Cold Floors & Walls in an Old House ~ What Can Nick Do?

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Roger is back to look at Skill Builder viewer Nick's insulation problem.
Here's Nick's message:
Hi, I hope you have some solutions to how to insulate these solid 9" walls and sub floor.
I've endlessly researched information about how to insulate and how to manage condensation but there are so many ways to do it and why you shouldn't that it's driving me mad.
To 50mm lime plaster these two walls is £3300.
Thank you for your time, Nick
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#AskSkillBuilder #diy #insulation
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[@rufioh]

I’d add that whilst the floor is up, they might have a chance to run some Ethernet wiring that their old house wouldn’t have had before.

[@wr3099]

Good idea but also an idea for those who do not have a chance to lift the floor - even if you're redoing carpet you can run a flat ethernet cable down before the new carpet and it'll do the same neat trick

[@DavidBrown-bs7gg]

I mean you could, but that will date too. Go wireless

[@SkillBuilder]

wired always beats wifi

[@MadDog_Rules]

@@DavidBrown-bs7gg For under the floorboards, that's why you run the ethernet cable through some cable protector, that's flame retardant and animal/rodent proof, that way if you ever need to replace the ethernet, you can just tie/tape to the end of the old ethernet and pull the new ethernet cable through. If you do lay it under the carpet, it's better to run it keeping to the outsides of the floor, so there's no traffic stepping on it every single day. Also hard wire beats wifi all day long. 🙂

[@DavidBrown-bs7gg]

@@SkillBuilder In terms of performance/latency yes wired is superior, but there are other factors to consider. Our house is over 200yrs old and we have 20+ rooms each with at least one device that requires a network connection. To run CAT6 cables to every room would be a huge undertaking, in terms of cost, time and potential damage to the fabric of the building. Instead we have a Wifi6 mesh with hubs dotted around the house that delivering at least 100mb/s to every room. This is acceptable for 99% of use cases, and can be deployed in minutes for very little outlay. To that end, I take a more pragmatic approach and would argue that wifi is NOT always the right choice

[@aledjones84]

Good advice on insulating the floor, that will make big difference. Roger should have pointed out that in the photo there appeared to be an air vent/ brick. Its important that isn’t blocked up as that suspended timber floor needs to breath underneath it. If using wool insulation just tack some vapour barrier at an angle to stop the insulation blocking the vents. Other option on the wall is to stud it out and insulate between.

[@michaelp761]

Absolutely agree, air movement is critical in preventing condensation build up.

[@assom1985]

I agree that the room has to breathe, but can I ask does the room need three vents and at the bottom? or will three holes in the top corner of the room covered by an air vent suffice?

[@krisholyoake7321]

Just done this to an old wall at home that was extremely cold. 3×2 frame with Kingspan in between, tape and join plasterboard. Nice and easy and very effective

[@user-nx8ii4ef7f]

Reading the comments, and my being due to upgrade a Victorian end terrace.....it is surprising the lack of consensus as to how to proceed! Such a common structure across the country too!!

[@univ01883]

Same! I'm exhausted by it, I don't know how to proceed, everyone has conflicting advice.

[@TheDavidsims]

I've just ripped out dot and dab plasterboard - the interstitial condensation meant there was massive mould growth and the board was very damp and crumbly

[@Confusedduckling499]

Were they external walls? I thought dot and dab was fine on internal walls but on the external walls, best practice was to stud to avoid cold bridging.

[@TheDavidsims]

@@Confusedduckling499 Yes external, the orginal lime walls next to the area were bone dry

[@peterjameswalmsley9185]

Roger said use insulated boards on walls which will stop condensation

[@eddiewilliamsmentalist]

Roger isn’t giving good advice, you would be better off studding or counter battening the wall first, bad idea to dot and dab on a house with no or little cavity

[@roversberg]

i just want to say thnx for the video's..they help me a lot in what to do and choose in a lot of ways..in my old house..guys..thnx !! from the netherlands

[@richardpope2114]

Spot on advice about the walls , I dot and dabbed the insulation board on with Soudal low expansion adhesive foam as it really sticks to the board and the wall and about the same amount as normal dot and dab but with extra at the top and bottom on the board ( PVA wall first ) but buy it in boxes of 12 as it works out £7 a can not £18

[@noneofthegearnoidea]

Ty Mawr Lime sell a lime plaster system that includes a cork board for insulation that you can plaster straight on to. Can be used internally and externally. Worth giving them a ring, they're technical support is really helpful.

[@emmaearnshaw3282]

They also do wood fibre based insulation boards that you can render straight onto with Lime plaster, that way you'll keep the walls breathing a bit, and its a lot cheaper than cork. £3k is to much, so, keep looking for someone and make sure they use lime putty, not the Nhl stuff.

[@rumusic787]

Ive used that on my single brick rear extension. Works well.

[@freebornjohn2687]

What's wrong with the NHL? I've spoken to Mike Wye consultants and other lime experts and they recommend it if you want to mix your own render up. @@emmaearnshaw3282

[@lksf9820]

@@emmaearnshaw3282 The problem with wood fibre boards is you need a dead straight and flat surface to fix them to, apart from that their system looks very good if you adhere to it all.

[@richardsandwell2285]

If possible I would always try and install a couple of access traps for access for either crawling underneath if deep enough or even just being able to thread future pipes or cables. Conduits can sometimes negate the need, but it is all about thinking long term and future proofing.

[@stephenmatura1086]

Personally, I try to avoid nailing or gluing floorboards down, preferring to screw them as you never know when you might need to lift them at a future date.

[@Tom-hl7wc]

It will squeak and that doesn’t meet current regs.

[@adamuk73]

I put access hatches in mine to but there's a lot of room under my floor

[@8bitsim]

Fine with traditional boards but if they are t&g chipboard as is the case here you can't lift them anyway unless the whole lot come up and even then it would be difficult with the skirting in the way, they really should be glued

[@venividivici1401]

Screws will also penetrate the vapour barrier 👎

[@waynemoore8615]

If there is a vapour barrier, then you would only be gluing the boards to that, and not to the joists, so the whole lot can move all day long and squeak whenever it likes.

[@richardghost5701]

Brilliant advice there. Solved my challenge with a cold internal wall.

[@phooogle]

I live in an old double brick house with no air gap circa 1930s. I've done everything I can to the point of external boarding now :) Works well, but never be as good as doing it properly from the ground up.

[@martinaxford47]

It depends if he wants it to be breathable. I've just done a similar job, we used corkboard, which we stuck to the walls with a lime based adhesive. Then lime plastered over the top of the cork. It is a more expensive method, as all the lime products take longer to cure and the process is slower, so more labour cost. I work in Cornwall and Devon where we have a lot of natural stone buildings held together with lime mortar. Breathability is very important for older property's, often sealing them up with modern materials causes more problems than it solves.

[@lksf9820]

It isn't what he wants, it's what the building wants, that's where most people go wrong.

[@ETH92]

But if you don't have effective vapour control layers on the warm side of the insulation then any air that passes through the "breathable" plaster and insulation could condense on the cold wall behind. "Breathability" of individual materials is not the important factor, effective methods to keep relative humidity low and the dew point high are, and there are multiple ways to achieve this.

[@danielnorcli]

It would be good if Skills builder could do a video on spray cork insulation for solid/ old walls. I believe it can be as thin as 8mm and can be plastered directly. This is something I am looking at as there are areas that wouldn't fit PIR or other boards.

[@shumbaiscool]

We have an old house and we used the woodfibre system. Then it’s all breathable, very warm and we just used the lime solo finish coat over the top, looks amazing no painting required. But if you do paint; then make sure it’s breathable. These old houses with no cavity wall or very tight cavity’s, are designed to breath. Respect that and you won’t get any damp

[@DIYpozer]

Am doing the same thing right now actually! Got any photos you can share? Always curious :)

[@dugandav1]

Also, it looks like you have some support underneath the floor joists, please make sure you provide enough support for the insulation board such as kingsman. Otherwise there is a risk that even if the board is cut to a tight fit as the joists expand and contract that eventually the insulation board drop out. Good luck with the refurbishment.

[@stuartclarke9241]

Ive started doting and dabbing all my walls with insulated plasterboard i have a few external walls then plastered and the difference is incredible ive not connected my radiator yet its december so its getting colder and the warmth of the room is brilliant. GET YOUR HOMES INSULATED its worth it !!!

[@yesmarioo]

Is it safe to dot and dab cavity walls that get cold in winter. I am thinking about doing it but afraid l will get moisture trapped between the wall and the plasterboard and condensation. I live in a 1906 Victorian house so moisture is always a concern.

[@stuartclarke9241]

@@yesmarioo My walls are cavity too the idea with cavity walls are that the outer course should be the one that would potentially get moisture from temperature changes and solong as you haven't filled in your cavity (making a connection between walls for moisture to travel between) your internal course should be less reactive to the external temperatures I also did a PVA/Water mix on before doting and dabbing the internal wall. I'm not saying this is the right way but this way has worked brilliant for me and the room I'm on about has two external walls as I'm on an end terrace built in the 40's hope this info helps you.

[@yesmarioo]

@@stuartclarke9241 thanks for the tips, appreciate it.

[@stuartclarke9241]

@@yesmarioo No worries let us know how it goes 😃

[@Hew.Jarsol]

@@yesmarioo Same ere!

[@mikeheasman2594]

If you screw the boards down they wont squeak, its the board moving up and down on the nail shaft that makes the sound.

[@TheBigSugs]

Roger, if you put a vapour barrier on top of the joists, you then can’t glue the chipboard flooring on to the joists. Personally I’d recommend gluing the boards and not bothering with a vapour barrier.

[@thomasherrin6798]

The vapor barrier (Foil) is already on the foam insulation normally, it can be on one or both sides too, just mastic or expanding foam around the edges of the foil to the wood if you want a complete seal!?!

[@zassakavuma5877]

Only the joints of the boards need to be glued for building regs

[@SkillBuilder]

BigSugs I agree it does hardly anything and you are right about the glue

[@philipshore6924]

Can you explain what you would do on the window wall and how you would join up to the window and get a nice finish? Great vid, btw, very educational.

[@Jhhhf4479]

There are lime plasters with added insulation. Great for heritage buildings. Now far U values less than PIR but still might be considered. There are also such thing as breathable insulation boards like Redstone calsitherm climate board

[@james.telfer]

I've put Rockwool between the floor joists to replace the mostly missing thin planks of styrofoam the builder who owned the house before us tacked in. The Rockwool is just friction fitted between joists so doesn't need precisely cutting to size & it's not going to fall out because it's so firm.

[@Retro-cabin]

Subsites contain a lot of moisture and with rising water tables could have a few inches of water in now and again. I wouldn’t insulate the floor joists as I have replaced many a floor with dry rot outbreaks. I would put more plastic air bricks in and keep the underside nice and fresh, cold air does not rise. They could always put a thin layer of insulation on top of boards and combined with underlay and carpet would be ok. I would 25mm roofing batten the walls isolating the brick work with a plastic dpc to prevent any low level damp affecting the plasterboard. Then use 25 kingspan inbetween the battens and plasterboard on top. Or might be better to use an open cell insulation so any moisture can permeate.

[@patrickdrewello4196]

Would use mineral wool insulation in the floor - agree on the vapour barrier…. the other consideration is if the brickwork wall which the floor joists are supported on has no DPC… using mineral wool allows any moisture from the wall which travels into the timbers to evaporate down and be taken out via the air bricks…alt. as you have access to the joists, I would wrap them in a DPC before slotting them back into the wall and then do the PIR…

[@barneyc4919]

Insulated plasterboard seems the best idea but maybe not too thick otherwise risk of interstitial condensation?

[@matticulas]

Not if it's a solid wall, which is likely with this age of house. Insulated plaster is impermeable whereas you need breathable (or vapour permeable, if you prefer) so that air can pass through the wall and remove moisture as it goes. Otherwise water in the wall, from outside water/humidity, can't escape quick enough and freeze/thaw cycles will damage the structural fabric of the building. Internally if you have impermeable plaster then you need adequate ventilation to keep humidity in check. Lime plaster is naturally breathable but you can add hemp or cork to it insulate or use wood fibre board or aerogel matting underneath the plaster. Lime is easy to plaster with for a novice so he could do it himself as £3k is way too pricey - the materials are still a little pricey though so it will cost more than gypsum.

[@thomasherrin6798]

They apply adhesive expanding foam and two screws into wall for each board (Thickness of plasterboard plus insulation plus 50mm for screw length) at 3/4 height of board these days, not dot and dab, refer to KZbin videos (Screws must be applied to keep boards in place for so long in case of fire!?!

[@jmerica4818]

I would think the last thing you would want to do is insulate/seal the breathing ability of the brick from the inside, leaving it exposed to freeze thaw outside. Isn't this why most brick historic buildings are falling apart on the outside?

[@craigrodgers9693]

Absolutely correct. It is terrible advice. Increases massively the likelihood of ceiling joists rotting, the ends of the suspended floor rotting, and any wooden lintels decaying just for a start.

[@Hew.Jarsol]

How would you insulate the wall then?

[@jmerica4818]

From the outside is the best of not really any great ways. That way the brick becomes the heated part of the envelope.

[@craigrodgers9693]

@@Hew.Jarsol wood fibre, insulating lime render, there are even 'plasterboards' 'made of lime now with a breathable adhesive. Many options. The original questioner in the KZbin video asked if he should use lime. It appears they understand how a solid wall works more than the skillbuilder

[@jonathanjackson6457]

Bought my first house two years ago and have been renovating it on a low budget, I didn't want to buy the big thermal boards as the costs quickly add up for every room. Instead I bought standard plasterboard, used the plasterboard foam spray adhesive, sprayed a pattern onto the back of the board for adhesion, then I used standard insulation foam to fill any empty space on the back of the board and stuck them onto the wall. End result was cheap insulated 'foam' boards on the wall. Obviously not as good as proper insulation as it's not as thick, but still really pleased with the results.

[@wr3099]

Ingenuity pays off. I did something similar for the eaves (arches) on my upstairs rooms. They were really close to the roof tiles and a condensation magnet. 25mm insulation board, and 12mm standard plasterboard on top.

[@Flashjohnsparks]

I'd fill the floor with concrete, 100mm insulation,underfloor heating and 100mm screed, walls insulated plasterboard using foam to stick it on, maybe blue grit walls 1st.

[@mkij7987]

Whatever way you decide to insulate this floor it is critical that you check the floor vents, ensure they are clear, then do a calculation for the ventilation requirement for a modern suspended floor. My calcs usually indicate that more vents will be needed. Also, older houses may have new paths or patio slabs increasing the level of the paths above the level of the subfloor, this will allow water to migrate to the subfloor with potentially disastrous consequences. Keep an eye on the subfloor with a hygrometer if you can, check every few months for around 2 years, just to see if it's trapping moisture. Good luck with your renovation.

[@hoobsgroove]

Good advice

[@monkeyboy8424]

If you dot n dab plasterboard to a party wall each dot will act as a sound transmitter. Seperate from the wall with a stud/metal frame. Only dot n dab internal walls.

[@Hew.Jarsol]

Yes

[@burwoodbuild]

With period properties making up a huge % of 🇬🇧 housing stock this advice will certainly help a lot of people! 👍🏼

[@nickbutcher8389]

Thanks Roger for posting this, the problem with making a decision on insulation on solid walls is there is so much information out there on how to do it and not to do it, a lot of it is conflicting. To improve the EPC they want a minimum of 50mm insulation, my concerns of using PIR is the release of toxins and possible shrinkage. My original idea was to cross batten with breathable superfoil and then plasterboard, which would allow moisture to travel both ways through the wall, unfortunately I can’t find any feedback out there of it being used to give me confidence in it. There is so many issues with insulating homes incorrectly which can be costly to correct in the future, thanks, Nick

[@lksf9820]

You need a breathable insulation system, there is loads of expert advice out there if you look around.

[@janoginski5557]

You could render the brick wall with a Lime render, which can be gauged to ensure no cracking or at the minimum mitigate against the possibility, the great characteristic of Lime is that it breaths and you will not get condensate on the surface, unlike a cement based render. £3k is heavy I would say, but depends on the area to be rendered.

[@catabaticanabatic3800]

£3k? Someone is having a giraffe.

[@ricos1497]

I'm guessing the area to be rendered is London!

[@petesshed]

@@catabaticanabatic3800 ... yeah and a long neck one at that! ATB

[@petesshed]

@@ricos1497 😂

[@ionwerks]

Was hoping you might touch on Aerogel insulation under drywall. It's an amazing thermal insulator and very thin, I just don't know what the implications are in terms of breathability.

[@pumpkinhead456]

Perfectly breathable

[@rm9719]

Horrendously expensive though

[@pumpkinhead456]

Wood fibre insulation is an excellent product for insulating floors. You cut it oversize and it squishes gently in to make an air tight seal. You can run a breather membrane over the joists and under the insulation. For the walls, build out a stud wall to allow an air gap, or use a breathable product like spacetherm wallboard.

[@PaulSmith-pr7pv]

This over under is what I’ve seen other KZbinrs do. Although Rog says it should go over the insulation.

[@pumpkinhead456]

@@PaulSmith-pr7pv Rog said a damp proof membrane should go over, I'm suggesting a breathable membrane. It allows moisture to travel between the room and floor space, albeit in a very controlled and healthy manner. Much more healthy than wrapping your floor in stinky plastic!

[@stevend9960]

@@PaulSmith-pr7pv with all due respect, Roger is not a carpenter or a builder and his knowledge here is basic. He's recommending it the way the blaggy bodgers do in London which is wrong. There's so much wrong in fact, that almost everything he advises here should be disregarded.

[@waynemoore8615]

​@stevend9960 Then what SHOULD someone do instead? No use criticising someone's ideas if you don't offer a "correct" alternative. Some say the vapour barrier should always go on the warm side of the insulation. Some say put a vapour barrier on top of a concrete floor before putting the insulation down, then timber "floating floor" on top. Then that would be on the cold side. Does anyone know the real way? Or does it make no difference? Assuming that vapour is carried in warm air, surely it would rise and not fall to floor level anyway. Also I've been told not to use PIR insulation in a suspended floor, but use a breathable type (wood fibre, lambs wool, or hemp) with breathable membrane below, and vapour barrier above. There is still the issue of that vapour barrier being punctured by every single screw or nail. Anyone know the best option???

[@liam_j82]

Expanding glue is a must like your said roger, stops any noise and bounce, very messy glue but does a great job

[@telstar4772]

Hi Roger what video is the clip of Robin fitting the insulation under the floor boards from, I`d like to see how he fixes it in place and any other tips in more detail. Thanks

[@JoannaLouise200]

I am steadily wall insulating the whole of my ground floor Victorian flat by CLS battening out the whole wall with lengths & noggins (taking wallplugs/securing screws into brickwork below sound original plaster, then insetting with Kingspan/Celotex/Iko ultratherm or any of those insulating boards (min depth 25mm), then plaster-boarding over the whole lot. It takes forever doing it this way, but I never want to have to do it again! It keeps my rooms warm and provides some sound insulation.

[@SkillBuilder]

Are you putting in a vapour barrier?

[@JoannaLouise200]

It's laborious, but have been sealing all outer edges of insulating boards (where they meet CLS battens) with flexible decorators caulking, and am using metallised polyester (silver) backed plasterboard (screwed down to CLS battens) to finish. I'm only a DIY-er so hope this will be adequate! BTW Roger, I used to listen to you on LBC many years ago. If I remember correctly you had a regular DIY problem-solving slot on the Therese Birch (phone-in) show? Used to really enjoy your expertise & advice...still do! :) @@SkillBuilder

[@Grey_Area570]

What would you do on cavity wall insulation; we have a similar situation, lime mortar, soft red bricks on a slate dampcourse with 2" cavity.

[@michaelgoode9555]

With floors up and bare walls it is a perfect opportunity to run in networking and power cables. More sockets and network outlets are never wasted but do plan them carefully. Oh, and take pictures of the cables on bare walls and in floor / ceiling voids before you cover them for future reference. Similar for pipework in kitchens, bathrooms and en suites of course.

[@JaenEngineering]

Just run any cables according to the regs and there's no need to photograph for future reference.

[@shaundavey5938]

im thinking about digging up my cold concrete kitchen floor to replace with insulated block and beam.Would i need to ventilate this?Its one room only.....

[@tom314]

Excellent thank you, I need to do exactly this after christmas. It would be great to add some more details about how you would deal with the interface of the insulation board with the windows? Do you need to worry about condensation occurring on the uninsulated internal wall where it acts as a cold bridge to the external wall and if so how you'd deal with it? I have a feeling I might be overthinking this....

[@thomasherrin6798]

Paint it with black bitumen paint on the window jambs and apply an uninsulated plaster board with mastic adhesive over the bitumen once dry is one method and it works, black bitumen is messy though so gloves and cheap brush!?!

[@PercyJackson93]

Any good ways to suspend the insulation invetween the joists? I have just ordered some fibreglass insulation but its in a roll, not solid to be just push fitted tightly inbetween like others are doing here.

[@tospicy4ya]

Couple of questions about of new roof we've had 4 jetliner window s fitted one leaks when I looked at it 3 of then the front flashing is recessed so pools water can they be lifted after installation I know there are height adjuster on them for different roof tiles and also the roof beams are 70mm thick so if I leave 50mm gap and then Kingspan will only be 20 mm insulation if I use plasterboard with insulation I'll eat in the head height of the attic any ideas?

[@gdfggggg]

I do quite a bit of work on old buildings. Had flats that were damp, in various places. Some was a result of external ingress of rainwater and others were a result of condensation. I tried to resolve both issues: 1. I removed all of the old lime plaster on the walls 2. Did a 50/50 SBR mix X2 coats on the bare brickwork (stops salts from fireplaces and external water ingress) 3. Dabbed 50mm celotex to the walls (taped joints. Vapour barrier) 4. Fixed plasterboard onto celotex with Soudal adhesive (insulted plasterboard is very expensive) Worked perfectly so far.

[@SkillBuilder]

How did you dab the foil face of the board, did it stick?

[@gdfggggg]

@SkillBuilder yes, fine. You can dab foil backed insulated board straight onto the wall, so there's no reason not to dab celotex onto the wall. Worked well for me.

[@gdfggggg]

@@SkillBuilder I dabbed with normal powder form adhesive.

[@gdfggggg]

You need to fix the celotex after dabbing with mechanical fixings. They're a 10mm plug with large head that has a push in centre. Make sure the adhesive is dry.

[@robjworkshop5692]

Saw a guy in Warwickshire on YT who recommended InstaStik or similar (Mega stik?) for the pir to brick, then Everbuild clear silicone (glue/sealnat) for the plasterboard to pir (pir and p'board cheaper than just insulated p'board). I can't remember if he said to PVA/SBR the p'board first for better adhesion, but I probably would anyway. Gonna do my kitchen next year (stone walled cottage) this way. Ty Mawr lime just up the road, did look at the woodfibre board option, but getting it all lime plastered too many £££. @@gdfggggg

[@DerekTJ]

I had my suspended wood floor insulated like this last week in a 1949 Dublin semi-d - the difference is unbelievable. The room would cool down in about 10 minutes when the heating went off but now there is a very constant ambient temperature without the heating. I personally would advise against internally insulating as the heating would never be absorbed by the masonry/walls. Insulated externally.

[@lksf9820]

EWI is much less risky than IWI, but it also comes with many downsides and complications.

[@waynemoore8615]

​@@lksf9820 I'm consideration getting EWI. What are those drawbacks?

[@lksf9820]

@@waynemoore8615 Google it. It would take me a long time to type it out here. Roger has done a vid on it and there are countless other free resources available on the internet which discuss it.

[@mikestork3223]

Was looking in to insulating floors before and remember advice on leaving bottom part of the joist free from insulation because of moisture? Gave up in the end as so much conflicting information on the net, can you give your opinion on this matter as the boss is nattering about replacing all carpets again and won’t to do a proper job, same situation solid brick house suspended floors.

[@patrickwasp]

What about adding a stud wall with rockwool?

[@JasGawera]

Also make sure air flow is all good before putting the floor down.

[@rumusic787]

Roger, this is timely for me. I have a Victorian End of Terrace house. No cavity on front elevation (gable end is) and I have been considering adding insulation board to the front either side of the Bay window and below. My question is would it be better to remove existing internal render 1st or just board over it? External is rough cast. Thanks so much.

[@lksf9820]

Why are you asking a plumber on YT to give you advice on several thousand pounds worth of work? Wake up ffs.

[@kirkby0076]

A Decent Miltifoil for the floor... Insulation & vapour control barrier, all in one, for the floor. Maybe the wall also, or insulated plasterboard with vapor control, sealed tgrn a decent graphite infused wallpaper, then a decent wallpaper liner, then a acrylic thermal paint, in a colour of your choice haha..

[@WoodworkJourney]

Any advice for insulating a concrete floor? We’re in the process of buying a bungalow with concrete floors, obviously adding an insulated floating floor would be an issue with height. Is the foil bubble wrap stuff worth putting under a carpet?

[@SkillBuilder]

You can buy some excellent foil faced carpet underlay. Just check is ok for your carpet. I don't think it is good for carpet with a high wool content. Talk to the carpet shop www.simplyunderlay.co.uk/product/qa-powerwalk-silver/

[@Tparker51]

How do you stick roof felt down?

[@Pete.Ty1]

👍👍👍.Thanks

[@2frogland]

our house is 300 years old 16 inch solid walls we had our room 14 ft square lime plastered for a few hundred quid using nhl2 and a lime top coat nhl2 is about twice the price as std cement

[@NoOne-hv1wz]

That’s cheap for a full room

[@growingknowledge]

Check the SPAB best practice on insulating old buildings. You aren't letting the building breath with modern materials which are better suited to modern construction.

[@SkillBuilder]

I think there is useful information in SPAB but there is also a lot of bolocks.

[@growingknowledge]

Fair play

[@lksf9820]

@@growingknowledge There is also a load of bollocks on the Skillbuilder channel, this ^ is some of it. Learn how to spell breathe though.

[@8bitsim]

You often find that the cavity has filled up with debris over the years leading to a bit of damp at the base of the wall where the dpc or cavity has been breached and the brickwork is often very wet. With good old dense timber and ventilation the joists on that front bay wall may not rot easily in their current state BUT if insulated and injected with foam to seal the gaps as Roger mentioned you could have some issues in years to come.

[@SkillBuilder]

It is good to consider these things but the joists don't touch the wall so the foam does a good job. I have never seen any problems with it.

[@8bitsim]

@@SkillBuilder Ok I couldn't see that but filling the perimeter space would bridge the gap between the previously isolated joist and a potentially damp wall, most foams soak up water quite nicely.

[@lksf9820]

It's a solid wall.

[@8bitsim]

@@lksf9820 A solid wall would be more likely to be damp at low level

[@adamwrigh8805]

What a great ding dong of comments !!!!!! Well done everyone ! Im certain Rog will revise and update Re IWI theres a gov publication & bristolian publication that basically says vapour open ( breathable) and swipiwi map that shows areas in uk for both open and closed !!! Im looking into it at the moment but certain its adding years on me and I aint got many left ...

[@gurglejug627]

I'd dot and dab polystyrene insulation onto the wall, then dot and dab plasterboard over the top. Or perhaps build a studwork frame if the wall is likely to move, in which to fit insulation, but that has its own issues. *Never* use plastic sheet in any building - tar paper (the thin variant like a roll of black card, not the thick roofing material) is better as it inhibits rot, doesn't create a cold area to attract condensation where it touches wood and if it gets soaked will give way such that one sees a problem (and water is released) before wood rots. It's also far easier and more pleasant to work with. For the floor, if there is space, i'd hang a layer of PU (Kingspan etc.) insulation under the beams before filling between them, to super insulate the room. I'd probably go so far as to insulate the ceiling of rooms, too, as we may face a time when we go back to being able to heat only one room much of the time - the cost/benefit ratio and return period combined with effectiveness considerations based on other factors in the house is of course a question for each household, but I say super-insulate every time - i've done it repeatedly in different countries and the feeling of quick warmth and lasting comfort into the night, or even 24 hours, is wonderful. I'd probably fit an inter-room adjustable vent in each room too, and probably one to the outside, to manage and optimise airflow around the house - dead cheap and simple to fit and nothing to go wrong. And i'd always fit a wood burning stove which draws cold combustion air from under the floor so that airflow under floors is enhanced.

[@thomass5364]

Is breathable insulation better here?

[@philipowen-dixon8492]

Great advice as always. Is it an issue dot and dabbing PIR board directly to walls? I was told to batten the wall first then fix to the battens (I had already dot and dabbed to walls before being told this). Not sure the reason, possibly air flow.

[@SkillBuilder]

I think the adhesive is not a good bond on the silver foil.

[@ss-xy2im]

@skillIBuilder Iam thinking of external wrapping a house (single wall) is it a problem to also put insulation on tbe inside?

[@SkillBuilder]

you need to get some professional calculations done and find the dew point. Most insulation companies will help with this. The danger is interstitial condensation.

[@southwestphotography-fj6iy]

Tekwarm Thermal Basic Insulated Plasteboard -- is this the product you refer, with regards to the wall ?

[@peter762033]

I've heard of some people putting up studwork and insulating between the studs but leaving a gap of 25mm or so between the brick and back of studwork/insulation to allow the wall to breathe. Is this necessary? Cheers

[@garethwynne1989]

Only on single skin walls

[@SkillBuilder]

You really want a dead air space if you are having one. The important thing is the vapour barrier on the warm side

[@vyvhuddy8381]

Some installers recommend putting a breather membrane (e.g. roofing felt) under the insulation (i.e. on the cold side) to cut down drafts. But might this risk slowing down the penetration of any moisture through the insulation so it condenses on the felt?

[@james.telfer]

Seems illogical; How would draughts penetrate a supposed continuous layer of insulation (unless they expect to leave gaps which is a poor installation)? As Roger said, putting the moisture barrier on the cold side would just trap it exactly where it would condense and cause damp.

[@brianbutterworth8043]

I’ve seen several videos advising to place the vapour barrier under the insulation, where mineral wool is used, to prevent wind washing heat away. This was placed over the joists and under the insulation. I’m about to start this on my lounge floor, is this not advisable?

[@SkillBuilder]

Brian It is true that you can cut down on the airflow across the insulation. It is only an issue on mineral wool and removing the air flow can cause mould on the cold side of the wool. I would say, don't do it. I put mine in over 20 years ago and it is fine

[@ranxxerox6407]

What’s the better solution for the wall? PIR in between treated batten’s (with DPC) and then plasterboard, or go straight to insulated plasterboard with dot & dab?

[@samnichols4361]

My personal view is neither I think a better product is something like the lime warm shell, which is a wooden fibre board which allows wall breathability. You lime render over and on top of it, allowing breathability of the wall from the outside in.

[@ranxxerox6407]

Ok, so are saying the lime render has a better R-value than PIR? I’m not tradesmen, but constant searches on the Internet show that PIR is the better solution to help warm up the house? And as long as there are no damp issues in the wall.

[@hdunnett3]

If it's traditional solid wall construction, you do NOT want to use plasterboard, the moisture through the wall will eventually ruin it. They do a insulating lime render product which is meant to be really good, then skim with a lime putty.

[@jackrussell9811]

could he batton the walls insulate and plasterboard if the rooms are big enough to lose a bit of space ??

[@stpeter7432]

Yes. I've done the same on our 1850s house with solid 9" walls. Like the floor insulation, I put a vapour barrier between the insulation and the plasterboard. Works well - no more mould behind the wardrobes and beds!

[@DrJohnners]

@@stpeter7432 Hi, just wondering how you sealed the vapour barrier round the edges of the room, the sockets and when screwing the plasterboard. I'm doing 2 external walls in an upstairs room but not sure what to do with the edges if the moisture can simply go straight behind the battens at the edges, ceiling and floor?

[@stpeter7432]

@@DrJohnners It's not a hermetic seal. I did this mostly for the insulation value to prevent condensation on cold exterior walls. I did a first fix for the electric cables and then fitted the insulation between the battens. I then stapled a polythene vapour barrier over the whole lot. Then I screwed the plasterboard in place. When I cut through for the sockets and switches, I cut the polythene locally and fitted the back boxes. Sure, there's a gap but there shouldn't be any significant moisture behind the plasterboard (unless the wall exterior is letting it in!) At the ceiling, floor and room corners, I turned the barrier round the edge of the plasterboard and trimmed it off flush before I skimmed it. I did several walls like this and have not had any problems in the last 15 + years. Good luck with yours!

[@michaelodonovan6989]

What about dealing with where the moist warm air goes in such a well insulated / sealed room? Won't you get condensation?

[@Adam-ui3ot]

Batten, insulation then plasterboard.

[@Hew.Jarsol]

Which insulation fiberglass?

[@oldclimber5502]

2 years ago I use PIR board ( both sides silver faced ) between the joists of my kitchen floor, am I going to get trouble as this effectively is a vapour barrier below the insulation ?

[@SkillBuilder]

No it will be fine. The only way moisture is going to get through from above is down the sides so the joists will wick it out to the underside. You have air movement under the floor so it will take any moisture away. We are talking about very small amounts.

[@newbeginnings8566]

Old houses need some modern mechanical ventilation system if you upgrade the insulation everywhere.. otherwise humidity will be a problem..

[@SkillBuilder]

humidity is always an issue, new house or old. I have to limit the scope of the answers otherwise they videos go on forever.

[@emmaearnshaw3282]

Or you use breathable insulation and plaster.

[@newbeginnings8566]

@@SkillBuilder truth enough

[@Hew.Jarsol]

Do you have to remove the internal plaster on solid bricks walls first or not? I hear if you Dot n Dab, it bridges cold spots and damp through to the plasterboard..? Can you use fiberglass behind the boards? Thanks.

[@SkillBuilder]

Just use thermal plasterboard. It is a vapour barrier and you don't get cold bridging on the dots

[@Hew.Jarsol]

@@SkillBuilder Thanks. So no battens on internal (exterior) walls? Just dot n dab? No need to knock wall back to brick? Or just dot n dab thermal plasterboard in the wall?

[@op9602]

Hi there Roger, so the insulated plasterboard from Wickes they don’t have a vapour barrier 50% of traders are telling me if is on a solid wall you don’t need it and 50% are telling me that you need a vapour barrier to the insulated plasterboard as the moisture will go in the foam and start stinking and gets mould . So which one is as it’s very cold and I wish to do this internal insulation asap. And on internet most people don’t tell you exactly what to do with or without?

[@stevenhall7659]

I'm in a similar situation with a 100 year old, very cold property so this video is very interesting. My property has a 55mm cavity with a porous, silicate masonry block outer leaf with lime mortar and internal plaster. An energy assessor is trying to convince me to have the cavity filled with beads but I'm not convinced it's the correct thing to do. I have been considering insulated plasterboard, would this be a better option? I'm concerned this would then cause condensation in the cavity, I'm totally confused now.

[@stevenhall7659]

​@@johnsealey5334Thank you for your response. Have you considered insulating internally?

[@johnsealey5334]

@@stevenhall7659 not really, just thick underlay, lots of loft insulation, dehumidifiers. Most of the plaster has lost its strength I apply watered down PVA when decorating to increase strength. Patch repair if necessary. Brrr old houses but more space than modern.

[@stevenhall7659]

@@johnsealey5334 Thank you 👍

[@stephennobes59]

Surprised you didn’t mention to use gapotape in the floor to make it airtight. It’s The Plumber

[@SkillBuilder]

Gapotape is an expensive option

[@stephennobes59]

@@SkillBuilder thank you for your reply Roger and yes you’re right it is bloody expensive but by got it does the job well. A building with 9 inch walls and have used 25 mm PIR silver on both sides for vapour and heat. Then a plasterboard over the top and worked out £5 cheaper than buying them combined. Like the Skillbuilder KZbin channel for all the various topics that you bring to, not just tradesmen, but also general public as well. Keep up the good work. Steve It’s The Plumber

[@samnichols4361]

Worth noting that any attempt to improve the thermal insulation of a property in an England does strictly speaking come under building regs. A big renovation like Nick is doing would require upgrade of thermal elements and needs to fit Part L of approved documents

[@8bitsim]

An extension or loft conversion would require this but just upgrading an existing element would not require you to comply with the approved document, you can put in as much or as little insulation as you wish.

[@samnichols4361]

The wording is vague in part L, rather than being so specific. It is always better to double check so you don’t get pinged later - building regs are mostly there for a reason

[@8bitsim]

@@samnichols4361 I speak from experience, I have done work like this and have spoken to building inspectors about it and you do not have to comply with part L for this type of work.

[@samnichols4361]

Fair enough I will defer to your experience on this one. My advice was slightly different when I enquired with local building control but I have not done the job yet so it doesn’t really matter

[@waynemoore8615]

​@@8bitsim According to the approved document to Part L, it states that if you are renovating or replacing more than 50% of any thermal element (wall, floor, ceiling, roof) then it must meet current building regs regarding u values.

[@ironimp1]

Fraught with potential problems. Many housing associations are now ripping out insulated plasterboard and PIR floors as they contribute to poor indoor air quality. My advice (as someone who works professionally within this field and therefore understands the science) is use lime and fibreboard, or other breathable products.

[@jonnygunner65]

Ventilation is the problem there…NOT insulation.

[@bland450]

Do you need to insulate all the walls or just the external walls?

[@dirtmcgirt168]

Internal walls in always nice. Not as important as floors, external walls or ceiling. Some home cold air flows from floor to roof so making it airtight or insulating stops that and reduces noise between rooms

[@lksf9820]

That looks like a solid wall, so it's very bad advice to put PU and plasterboard on it. It'll work ok for a few years, but slowly mould will grow behind and the joist ends get damp and rot off. There are so many people bodging up old houses now with inappropriate insulation that in decades to come builders will be cashing in putting it all right. Modern lime plaster mixes do not crack, we do it better now than they often did back in the day. Back then materials were expensive and labour cheap so corners were cut. There is no shortage of breathable insulation systems on the market now so aside from cost there is no excuse not to use the correct materials and systems. All you're doing is creating problems for future owners or yourself if you live there long enough, but then that's nothing new....

[@lksf9820]

Dangers of IWI: kzbin.info/www/bejne/fparYnVnotJ3apo All RIBuilds vids are worth watching as they explain fully and test what happens when you insulate a wall. Why using filler foam to fill insulation gaps is a bad idea and why the manufacturers have come up with better solutions: kzbin.info/www/bejne/h3vWmHp6pr6Aj68

[@danielabrahams4061]

I would stick with lime on a house that had it originally. There are lightweight insulating renders available with fibres using NHL2

[@SkillBuilder]

I think the £3,000 price tag is a problem for those two little walls

[@Hamishmcbeth]

Has anyone mentioned wood fibre board insulation with lime plaster? Completely breathable. Surprised dot dab with pir plasterboard was advised on a solid external wall.

[@SkillBuilder]

The whole idea of insulated laminated plasterboars is that if forms a vapour barrier. Brethable means it allows moisture in as well as out. Wood fibre with moisture migrating through is not a great idea

[@Hamishmcbeth]

@@SkillBuilderthis is a genuine question, not arguing with you, do you know why Historic England recommend wood fibre and lime products for solid walls in listed buildings? All they talk about is allowing moisture movement and breathability, therefore the opposite to what you’re saying. Help! 🙏

[@Jason-cr3lg]

He’s a menace to traditional built properties… I wonder how many out there took his advise ended up with wet walls, rotting timbers etc… 🤦‍♂🤦‍♂🤦‍♂

[@SkillBuilder]

Rather than criticising me you could have offered your non-menace version. Thought not

[@amritbhupal8514]

Do you not need to then ventilate if you’re going to insulate..?

[@user-xg5eo4nj9k]

If there is a need to insulate an external wall what would be better out of external insulation or internal insulated plasterboard? The external wall will be getting rendered anyway Thanks

[@SkillBuilder]

You can put a 100mm thich insulation on the outside but far less internally. EWI also means the thermal mass of the wall is insulated and can act as a storage radiator to even heat out over the on off cycles

[@TryDiy]

Also put double the amount of sockets that you think you need!

[@jacobcohen9205]

What thickness of insulated plasterboard should I put on a gable wall?

[@SkillBuilder]

As much as you can afford.

[@charlieholdontolove9392]

I live in 1895 victorian terrace house with 6ft height in the basement. I can't lift any wooden flooring up but can access into the basement by a small hole in kitchen. How do I put insulation under the flooring in the basement? As its something I want doing next summer!

[@waynemoore8615]

There is no definitive answer, cos everyone seems to have different opinions. I am in the same boat as you, and currently it seems the best option is breathable insulation (hemp, sheep's wool, or wood fibre) between the joists, with a breathable membrane fastened to the underside of the joists. Make sure you have enough clear airbricks below the floor. I don't yet know how much insulation you need (to satisfy building regs u values), but ANY amount is going to make an improvement if you're just trying to keep warm.

[@sunshinechild-sv9kc]

hemplime would be a great job on the walls

[@nicktaylor7680]

Why not put the polythene moisture barrier on the ground to stop the damp rising.

[@JohnnyMotel99]

Solid insualtion sheet is expensive today, rockwool batts would be less expensive and just as effective. Mind you s/h Celotex sheets would be an alternative.

[@asilver2889]

Kingspanseconds - Google.

[@wr3099]

I'm thinking of S/H celotex sheets too. Definitely not cheap and for my living room it looks like a mammoth task (average DIY guy here). How would you hold up the rockwool? Tie it?

[@johnbarleycorn7845]

Batts are quite rigid, so friction fit usually keeps them in place, however if you use more floppy loft type insulation yo can keep it in place by stapling scrim tape between the studs. Cheap solution and it works Don't forget your vapour barrier!!

[@wr3099]

@@johnbarleycorn7845 good suggestion. I was thinking more for the floorboards. Would you need a vapour barrier there? Not crucial, right?

[@JohnnyMotel99]

@@johnbarleycorn7845 I should have said batts are the way to go. I've used batts on internal stud walls and it has worked fine.

[@Bobbisox-wo7zu]

Are insulated dry wall boards available?

[@SkillBuilder]

Yes they are called thermal plasterboard

[@DlStreamnet]

Hi mate - you said cover in poly and then said glue to the joists. Doesn't that mean you are just glueing to the poly? I silver taped my PIR and overboarded - then glued joints of boards. I didn't bother glueing to joists as it'd just glue to silver tape...

[@SkillBuilder]

I wouldn't cover with poly, but I know some people like the vapour barrier. I would just glue the boards to the joists

[@TheDavidsims]

Foam rod round the floor edges - better than expanding foam

[@dougsaunders8109]

I am currently insulating a 200 year Georgian place with SuperQuilt under the floorboards which gives the vapour barrier and insulation in one

[@stevend9960]

This is the advice I'd expect from a plumber that reckons he knows about building, carpentry, and plastering

[@SkillBuilder]

I am glad it met your expectations.

[@andy8nic]

I would use insulated lime render and maintain the breathability of the building like it was built to do. Cement and gypsum don't work in old houses

[@SkillBuilder]

This line is trotted out all the time but it is complete nonsense. Old buildings were not built to breathe, they were built of lime because that was what was availalbe. It has now been placed on a pedestal by people who knit sweaters out of their beard clippings. I have always lived on old houses and I use gypsum plaster and have zero damp problems and no mould. We have carried out a number of vapour permerability test on sand and cement with plasticer and NHL 3.5 lime and gypsum plaster. The biggest problem with gypsum is that is disintergrates when it gets damp but that is why I suggested using thermal plasterboard. The airborne moisture will not get through and the exterernal moisture will leave the way it came in. I have a kitchen with solid walls and thermal board, as specified by the architect to meet the U values and it has no damp issues whatsoever.

[@ealingbadger]

@@SkillBuilder Sweaters out of beard clippings - love it! Agreed, old buildings were not consciously built to breath. It was just a happy accident (borne out of necessity) that has stood the test of time. Using gypsum still makes me nervous though...

[@brynmorjenkins4376]

What happens if you want to retain the original features?

[@robjworkshop5692]

I'd like to retain the exterior stone wall in my kitchen, but sadly, the cost of energy today makes this financially impossible, so I'll be using PIR board to insulate it out - changing times... :(

[@philipgardner-uz5ne]

Have used the sheeps wool batts,with no problems yet(3yrs) they could not get approvals!anyone know why??

[@emmaearnshaw3282]

What approvals, building regs? and is that behind plasterboard?

[@SkillBuilder]

infestation of moths is a common problem with sheep's wool insulation

[@philipgardner-uz5ne]

@@emmaearnshaw3282 not too sure,it may be the council?/or do they rely on building regs,+its supposed to have a moth deterrent added

[@ealingbadger]

@@philipgardner-uz5ne Deterrents only last so long...

[@InsidiousDr9]

are those 2x4 floor joists?

[@SkillBuilder]

yes