Underfloor insulation retrofit full demo

[@jonathanfletcher9533]

Steve, you have such a lovely calming fuss-free delivery to camera, the video was great to watch with a fantastic end result. Good to see the work done without an arsenal of uber-expensive tools. I recently did a very similar job insulating my dining room floor and found using a pallet breaking tool (sold at Screwfix, Toolstation etc.) massively sped up the floorboard removal process. looking forward to future videos 👍

[@JoanneMccorry-nicholl-zz9bx]

Great video. Very well explained. Feel a lot more confident about tackling this job.

[@SteveWardellDIY]

Glad it helped. Thanks for watching.

[@AlexeiTetenov]

Did you consider numbering the boards before removing them, so it would be easier to place them back in the same order?

[@SteveWardellDIY]

I did that for the next room and it’s a helpful tip. Thanks for the great feedback

[@Daz159100]

I really wish I did this when renovating my place rather than just lifting a small amount and shuffling along the ground, it was not air tight and im sure is next to pointless! nice video.

[@jwester7009]

12:20 I wonder if it wouldn't be better to screw a board to the underside of each joist? Then you get room for at least 100mm insulation

[@SteveWardellDIY]

Yes, that would definitely allow more room for insulation. I was keen to leave an air circulation gap under it where it passes over the timber bearers beneath, to help keep them dry.

[@neilsjmcmahon]

Very thorough. Don't think I would have had the patience to be that careful with the floorboards - reef em out regret at leisure

[@matthewcalder4351]

Brilliant job best video I've seen on this subject so far.👍

[@SteveWardellDIY]

Thanks Matthew. Great feedback.

[@Lord-Brett-Sinclair]

Nice work. I did a basic version of this 30 years ago with fibre glass loft insulation and a staple gun. Had to crawl under the floor and work on my back. 😢.

[@SteveWardellDIY]

Sounds like fun Andrew. Glass fibre up your nose 😂

[@jp6975]

Nice video - appreciate you posting it. I'm tackling this next month in the bedroom above my garage. Dreading lifting the laminate and the floorboards as everything is TnG. I'm dreading putting it all back together even more! I was cutting 100mm celotex last year for insulating the base of a garden room. Incredibly difficult to keep a 90 degree cut. I clamped a straight edge and used a jigsaw with a bosch blade specifically for this... and even cut the blade to 105mm but it still wandered. As I'm doing the bedroom, and probably the 2 rooms downstairs as well... as well as the garden room walls and roof... I'm thinking of buying a used insulation cutting saw and then selling after use.

[@SteveWardellDIY]

Great idea buying a second hand insulation saw. I don’t suppose you could insulate the bedroom floor via the garage ceiling instead?

[@danyo1972]

Great job. That’s a lot of work. I hope it’s cosy.

[@SteveWardellDIY]

Thanks for watching @danyo1972 it’s definitely better than it was.

[@stuartibbotson7179]

HI steve where did you get your carpet from I have been searching for something like that ,,thanks for the video too

[@SteveWardellDIY]

That was from Carpet Right Stuart. It cost a few bob but was worth it.

[@_Damian_.]

Nicely done, looks like it went quite well too. The same task has me daunted since I moved into my 1930s property 4 years ago!

[@michaelfraser5723]

never be daunted by tasks that test you

[@loosecannon5813]

Half of the task is taking the plunge and getting started.

[@SteveWardellDIY]

Hear hear! Having the confidence to go for it, and the staying power to see it through. Thanks for watching

[@SteveWardellDIY]

A dpm would go beneath structural components to stop moisture rising into them. This would be beneath the timber bearers that support the floor, for example. A vapour barrier would stop the moisture in the warm air in the room moving with the air as it passes through the floor and reaching a dew point. In the case shown the continuous aluminium layer creates this vapour barrier, and blocks moisture penetrating into the insulation or joists from the room.

[@pumpkinhead456]

Wood fibre batts are such nicer material, they can be fitted just using friction and require no vapor barrier (so you can leave a few boards down if it's a precious floor - mine was and I did). If you go down the smelly PIR route (the chemical smell turns my stomach) always wear a dust mask, you could also consider gapo-tape to get a tight fit. As an aside, it's much easier to lift nails with a bit if wood under your crowbar.

[@SteveWardellDIY]

Wood fibre batts provide poorer insulation for the same thickness. Friction will only overcome gravity if really tight. Better to support the insulation. The vapour barrier is to prevent moisture from the room entering the floor and a dew point occurring on the timbers. It’s not for the insulation. Leverage on a crowbar and the need for packing will vary depending on the height of the nail head, the amount of bend in the crow bar, the strength of the person and other factors, so it’s not really something that can take a sweeping guide. I use packers when the application needs it. Thanks for watching.

[@martinquinn7804]

Nice professional job and detailed documentary enjoyed watching thank you

[@SteveWardellDIY]

Thanks for the kind feedback Martin

[@martinquinn7804]

Your very welcome Steve and merry Christmas to you and the family 🎄🎅

[@ivanbeavon9050]

Brilliant video ! All that was missing was his Missus coming in and wanting to know how long it's going to take 😂

[@SteveWardellDIY]

In the time lapse video of insulating the other room Mrs Wardell can be seen sweeping up! Naturally curious to know when the job might finally be finished, but always lots of cups of tea and support. She’s a keeper. 😀

[@mcswainy]

Great video thanks. Need to do this in my 1930s semi. Got a slow leak somewhere down there to sort too, plus a number of other issues like rats smells.. Been avoiding it until the kids are older, but I think they might just have to live on a building site for a few months😅

[@1979com]

would be nice to get an up date on how the retains heat and heats up during this cold winter. thanks for the video

[@SteveWardellDIY]

Hi Mohammed, we’re in the first winter since installing, but I’m watching the stats carefully. It’s too soon to say but the room feels warmer than before, and it’s hard slowing the log burner enough to avoid over heating the room, even with the room door open

[@mrb3483]

Good job there Steve, fussy free no nonsense job, well done. (was it much warmer after that job)?

[@SteveWardellDIY]

Thanks for watching MrB. The room does not get as cold as it did, but doing this through the whole ground floor is needed to make the full difference. Also, beware the need for air to ventilate the fire/wood stove if you have one. This room now sources its air from the rest of the ground floor.

[@morganrobertson6865]

Thanks Steve for a very helpful video. I'm looking to do a similar job in our1930s house with 100mm joists but I gather this system wouldn't provide a good enough U value for current regs. I appreciate you probably didn't involve Building Control but they will be visiting the property as an extension is being built and I didn't want to be midway through this job when they are on site if I haven't told them about it. Do you think it is possible to insulate between 100mm joists over a ventilated crawl space in a way that would be approved by Building Control?

[@SteveWardellDIY]

@@morganrobertson6865 Thanks for the feedback. You’re right, I was improving from nothing to as much as I sensibly could based on the existing design constraints. Where retrofitting and limited by the design you’re obliged to do the best you can. I needed an air gap to allow air to circulate over the timber wall plates to keep them dry, and chose 25mm as a minimum for this, leaving 75mm for insulation. Building control requirements change with time too, so the requirements for new and unhindered retrofit will probably have changed since I was making the video. I recall retrofit used to be different and less demanding to new build. The approved document for this can be found here assets.publishing.service.gov.uk/media/662a2e3e55e1582b6ca7e592/Approved_Document_L__Conservation_of_fuel_and_power__Volume_1_Dwellings__2021_edition_incorporating_2023_amendments.pdf New build and retrofit both currently requires a maximum thermal conductivity “U” value of 0.18W/(m2·K), as per the tables on pages 24 and 25. I think I was installing the predecessor to GA4000. The data sheet for which is here celotex.co.uk//assets/tds-uk-insuk0003a-en-celotex-ga4000.pdf 75mm thick board, as I was using has an insulation value of 3,40(m².K/W) Using the Celotex site’s own calculator for a timber floor in a square room scenario 4x4M using 75mm GA4000 the U value calculates to 0.30W/(m2·K), so no, it does not meet current regulations. To achieve 0.18W/(m2·K) on the Celotex calculator in a between the joists arrangement, you would need Celotex XR4000 150mm minimum thickness, but you’ll need to confirm this using your room size for the perimeter/area ratio. If this is accurate then you’ve not enough depth between joists, but potentially could put 100 between and 50 under, depending on joist ventilation and vapour control design. Best chat with your building control inspector to confirm their requirements and get their advice, and this detail ought to have been in the design submitted to building control too, so may be worth checking that. Also worth noting the approved document says that the U-value of the floor of an extension may be calculated using the exposed perimeter and floor area of the whole enlarged dwelling. This will impact the calculation. Hope this helps.

[@martynbuzzing3327]

My floor removal job was a bit different, as the boards are tongue and groove, and were old sizing. Turned out a bit more expensive than I first thought. Informative video though, thanks.

[@SteveWardellDIY]

Thanks Martyn. Tongue and groove was a great way of transferring load between boards, and it stops draughts too. Pain in the arse to take up though. I feel your pain.

[@HealthTruthMovement]

Cheers for the video, food for thought!

[@philflip1963]

If your a skinflint you can hold the insulation up with string looped underneath it and nailed to the top of the floorboards with tacks. I done, (didid) this and it worked!

[@SteveWardellDIY]

Hi Phil, yes indeed, though the cold air beneath may circulate in any small gaps between joist and board, so a nice tight fit is needed. Great to hear your insulating your home too.

[@Alixstair]

I bet it's cosy in there now, plus the room acoustics are probably more pleasing!

[@SteveWardellDIY]

Thanks for watching. The room seems more sound absorbing than it was before. I assumed this was due to the heavy carpet, but am not an acoustics expert.

[@Aboutsixtwo]

I’m getting conflicting info about if a dpm or breather membrane is needed , fears of condensation/damp I have suspended floor same as you but not sure if I need more than in this video

[@thecatandthewitch3428]

Theoretically the celotex doesn't need any DPM, as it is already damp proof. The difference is the way it is laid on the joists I think, as it should be thigh and airproof (that's why he's using silicone in the video)

[@yorsoul1555]

Did you consider using Gapotape? It’s a spongy tape that fits on the edge of the insulation board and takes up any error and forms a snug fit on the joists. I went to a retrofit seminar recently and saw this product. You have inspired me to tackle this project but may replace floor boards with marine ply. Thanks

[@SteveWardellDIY]

Hi Yorsoul, it wasn’t a product I was aware of the at the time, maybe due to it being new to the market, so no I didn’t. I will be trialling it in the future though. Worth noting that battens to stop the board and sealing the gaps is a recommended method by manufacturers. It’s an airtight method. Hopefully Gapotape will be just as good, but it still needs a level of care in the cutting.

[@adamwilks]

You must have knees of steel! Great job.

[@MishMash22]

Great video. On such a difficult awkward job.

[@azerabdullaev2281]

I really enjoyed watching your video. You have done a really great job. Thank you for sharing your experience with us.

[@arnoldmonk6381]

Great job, I’ve been putting off doing ours for a good number of years. Has it made the room any warmer? We have the same type of floor with vents and the room is hard to heat. Just watching you made my knees hurt! Treat yourself to some trousers with knee pads in, don’t wait till you’re 60+ with bad knees😊 like me.

[@SteveWardellDIY]

Hi Arnold, thanks for the feedback. Yes the rooms feel warmer and heat more quickly. Stopping all airflow is a big factor in my view. Beware if you have an open fire or old stove, they need ventilation and this will reduce it.

[@MrGlenfraser]

@Steve Wardell How long did that take you to do???

[@SteveWardellDIY]

It’s a few days from start to finish, depending on what other stuff you’re doing.

[@sextonblake4258]

Nicely done. Couple of suggestions: 1) a rip claw hammer might be handy. 2) a tool for dismantling pallets might work better in places than a crowbar. 2 prongs sit either side of the joist and you get lift in 2 places. Means you don't have to force your way between the joist and the board. I pre drill the batons and then use the driver,which is shorter. Celotex is a good choice. Anything fluffy might need a thin sheet of ply to keep furry friends from making a home.

[@SteveWardellDIY]

Thanks for watching and for the tips Sextonblake. I’ve never owned either tool so will look them up. Fluffy insulation would be less insulating and may allow airflow through too, so I’d avoid it. If a subfloor has rodents in it their access routes need to be stopped as soon as possible. Chewing cables and other damage could be a much bigger problem than nesting, as would their eventual ingress into the rooms above scavenging for food.

[@pianomanjc3]

Yes. I have one of those tools; fantastic. Also meant it was easier not to damage the boards.

[@weihaihu2265]

Thank you for your 40 minutes

[@mikeheasman2594]

Nice work, my floor boards weren't that great so screwed them to the underside of the joists to support the insulation. Renewed ring main just in case and removed rads, replacing with underfloor heating.

[@mcswainy]

Great idea, was just thinking of doing something similar myself. That would also allow for 125mm insulation presumably if joists are the same size.

[@SteveWardellDIY]

It’s a good reuse of the boards. My joists are 4” so limited to that for insulation

[@user-su1bi8xx9d]

We just moved into a house about the same age. Wed really like to insulate the house better. There are currently solid oak floors throughput the downstairs (not original but beautiful and good quality). Unfortunately when they were placed i dont think insulation was put down! You seem fairly DIY savvy!.. could it be possible to remove and reuse the oak floors if we did something like this?

[@SteveWardellDIY]

Probably yes, but you need to find out how they were laid. The oak may be tongue and groove. If so you’d need to start with the board that was last to be laid last on one edge. Take a look along the skirtings and see if you can work it out. Beware they may have used adhesive. If they have then it may not be possible to separate them without damage. Hard to give accurate advice without seeing it though.

[@WHATSUPWATSON]

Can you feel the improvement in floor temperature?

[@djm4160]

I walked on under floor heating you can definitely feel it I’d say better than having radiators

[@SteveWardellDIY]

Yes, the lack of draughts, particularly around the edge is noticeable. Thanks for watching.

[@RooibaardBoerseun]

Should the insulation not be up against the bottom of the floor boards? Leaving an air gap leaves potential for damp to accumulate between the top of the insulation and bottom of the floor… isn’t it..?

[@SteveWardellDIY]

An interesting theory, but the upper insulation surface should be the same temperature or close to that of the room, so no risk of condensation forming. A small gap may allow minimum air circulation around the boards, but I doubt it’s needed. The boards will breath to a limited extent through the underlay and carpet above, but cannot get moisture from below due to the continuous foil layer atop the insulation.

[@RooibaardBoerseun]

I was surprised to see that you installed a carpet is it just your preference ? I know many people don’t particularly fancy the wooden floors but you went through all that trouble I thought you will have them sanded and refinished. Would condensation pose a problem should the carpet and underlayment be removed in the future?

[@SteveWardellDIY]

@@RooibaardBoerseun I think condensation would be even less likely if the boards were exposed. I wanted a comfy feeling underfoot, because it’s a sitting room, hence the carpet. When I did the kitchen I replaced the boards with new solid oak and left them exposed. It looks great. Sanding old pine boards produces a nice finish, but they dent easily and it thins them sanding off enough to leave them clean. I’ve done a few rooms that way in the past with nice results, but it’s a dusty job too, using a floor sander.

[@AlexeiTetenov]

16:35 Did you need to level the floor, so it would be perfectly flat?

[@SteveWardellDIY]

Yes indeed. A six foot level was used regularly

[@thecatandthewitch3428]

Hi Steve, my hubby and I enjoyed your video somuch that we wanted to try the diy upgrade for the insulation in our 1880 cottage. What makes me doubt about the chance for us to succeed is that in our case the air ventsare above the level of the floor...so I don't know how much the insulation would be effective and if it would be recommendable to consider it.

[@SteveWardellDIY]

The effectiveness would be much less with the vents above the floor, and sealing the void with the insulation with no ventilation beneath could lead to unwanted moisture build up and timber rot beneath the floor. Best have it surveyed by an engineer before deciding the best course for you.

[@thecatandthewitch3428]

that is exactly my big concern. Thanks Steve@@SteveWardellDIY

[@thecatandthewitch3428]

Me as a diyer, the only option Isee here are telescopic underfloor vents@@SteveWardellDIY

[@Sara-sd4lo]

Hi, would you recommend adding a Damp Proof Membrane under or on the top of Celotex? Planning to do the same but using Laminate flooring instead of carpet, thanks!

[@SteveWardellDIY]

Hi Sara, probably not below, because the upper foil layer will be a vapour barrier. Adding another in a different place may trap moisture between. I don’t think one is needed above either, because the foil layer does the job.

[@jimirons833]

If you would be so kind where did you get that carpet and underlay from looks perfect for a room I have to insulate TIA

[@SteveWardellDIY]

Carpet and underlay came from Carpet Right, but the same underlay I found cheaper elsewhere when I did the next room. Tredaire - Kensington Deluxe - 11mm - Carpet Underlay - 10.96m2 amzn.eu/d/4i8aFI8

[@jimirons833]

@@SteveWardellDIY thank you so much 🙏 ps don’t change your mic keep it real

[@SteveWardellDIY]

@@jimirons833 no probs. 😀

[@giuliosarchiola]

Great video. Thanks for posting. I’m considering doing the same thing but i’m worried the lack of air circulation could create dump and rot the wood. Is that a risk? Thanks

[@SteveWardellDIY]

So long as the sub floor is ventilated properly at the main wind loaded and opposite side, so that fresh air circulates beneath the insulation, the risk of damp should be reasonably controlled. If you are very concerned you could look to install a dpc across the underside of all timber elements, but it would mean lifting the joist bearers to get it under and behind them.

[@hewoguys2506]

good job but i would of put a dpm on top of insulation then boards coz yes its all good having everything air type but if u havent left enough air flow between floor and insulation it will sweat so when you are insulating creating any air flow just as important

[@Jonnysonone]

So the ‘air gap’ you have left under the floor board and above the PIR…what prevents that from condensing with temperature changes?

[@SteveWardellDIY]

The gap and upper surface of the PIR is at or very close to room temperature, not cold, so will not be a space or surface creating a dew point.

[@paulboyle8522]

Great video mate, really helpful. I’m going to have a crack at this in my living room. Was there much wastage as those sheets are not cheap?

[@clivewilliams3661]

I would have maximised the floor insulation to get the greatest benefit. Whilst the 75mm board is not up to current regs, the regs are on their inexorable way upwards and 75mm will soon be seen as mean. The reason about retaining air flow over the dwarf supporting walls does not stack up because it is very easy to chop out individual bricks in the 1/2 brick wall to promote air crossflow without any real loss in structure. The thicker insulation board can be supported on nails or screws driven in to the sides of the joists instead of battens that take up too much space. Indeed, even greater insulation than the depth of the joists can be installed using standard stainless steel door frame cramps.

[@SteveWardellDIY]

You’re right Clive, about the dwarf walls. More importantly I want air to get to the end supports that are onto the external walls. These are the ones that have suffered most rot historically. The battens provide an air seal to the joint between board and joist. It’s a critical component I wouldn’t remove, even for an extra 25mm depth. 75mm is already mean. It should be twice that, but it’s a huge difference from air flowing and no insulation to a sealed 75mm solution, and not that much more when doubled up. Thanks for the feedback.

[@clivewilliams3661]

@@SteveWardellDIY One alternative would be to incorporate a a composite solution say, using multifoil draped over and between the joists with a thinner PU foam board between the joists That would overcome the concern about air tightness and create a full vapour proof skin. I have used multifoil very successfully that has outperformed sole PU installation that means we aren't reliant on over deep constructions.

[@SteveWardellDIY]

@@clivewilliams3661 I’ve not used multifoil before, but it’s sounds like a good option. What’s it like to work with?

[@clivewilliams3661]

@@SteveWardellDIY Relatively easy and it comes in a 1.3m wide roll x 5m long, you simply roll it out. Joints are usually overlapped and if necessary taped with aluminium tape, giving a 1.2mm working width. The material fluffs up about 25mm but is easy to handle and fixings are normally stainless steel staples. The material is draped over joists and the like and is crushed when finish boards are fixed over the top, this creates a thermal and vapour barrier. The system relies on an airspace of 25mm on each side of the multifoil to maximise performance that means the construction depth is 50-75mm before any additional rigid insulation or board finishes. I have used multi-foil as a sarking felt under roof tiles and then around and up into roof rafters that were only 100mm deep to give an insulation value that exceeds the current Bldg Regs best value. The issue with multifoil is that its effectiveness cannot be calculated in the standard way and relies on experimental results. I prefer to specify Actis Triso-10 as the customer service especially with thermal performance is very good, they also provide estimated performance for bespoke systems that is generally accepted by Building Control. Buying the various brands of multifoil from builders merchants is expensive until you factor in the cost of the labour to install it. However, multifoil can be purchased as surplus material at very advantageous rates.

[@SteveWardellDIY]

@@clivewilliams3661 this is awesome insight. Thank you for posting. I’m going to read up some more and maybe look at using some

[@barryfoster453]

Steve, sorry this is about two years' late, but can you say why you didn't just remove the joists, fill it with sand and then lay the PIR? Why leave the timber in? Thanks. Sorry, should have said, the reason I ask is because all that timber still has to be ventilated, so negating a lot of the insulation.

[@SteveWardellDIY]

Great question. There’s a few reasons. The space below the floor is quite deep and would have consumed around 8 tons of sand. That’s a lot of work. The weight of the sand would have placed load on the inside of the walls, and I’m unsure what impact that may have had. The ventilation air passes under this floor on to the next subfloor then the next so we would have starved ventilation from the rest of the house causing damp elsewhere if we’d filled it with sand. Sand costs money. The subfloor void is used for services such as water, gas, and heating pipes, and electrical cables. These may need maintenance access which would be much harder if there were sand there. If sand were used with a floating PIB layer we would then have needed a floating chipboard or concrete floor on top, which would have been more time, money and materials. I’m now starting to wonder why you would consider using sand instead of the existing joists. Let me know your thoughts please.

[@barryfoster453]

@@SteveWardellDIY Thanks for replying. I'm actually a heating consultant, and I was reading some work stuff this week about just how bad timber floors are at conducting heat, rather than concrete floors. I have to be honest and say that this was news to me (though I did know that there wasn't much in it either way) - when we do calculations, it's all done for us, we just input the structure and dimensions, etc. It appears that when everything is taken into consideration, especially ventilation of the existing timbers, it might be better to go with a solid floor. This can only be achieved by filling the void created. Concrete is out of the question, but sand is actually very cheap, at £39/850kg, so would only have cost you £312. I take what you're saying about services you already have running through, and yes, if the ventilation goes on to other rooms, it would need piping set within it. I think there's an argument, though, for when undertaking a complete refurbishment, for just taking all the timber out...sand, DPM, PIR, then a slab screed. There would be no weight on the side walls, by the way, as the force is primarily downward. You only have to be concerned about lateral forces when it is scaled up to considerable depths. I used to explain this to students - try getting on your weighing scales and then lean on the wall. The scales stay the same. It would be interesting to run it past BC and see what they think. Having totally refurbished two properties, I think I'm too old to do it again, but I still have ideas that I would like to try out.

[@SteveWardellDIY]

@ That’s really interesting Barry. We do just rely on those calculators and not really know. The depth at the front of the room was nearly a metre, hence the side load concern, but I agree it’s notably limited when studying the physics. The screed layer would need to be edged from the existing structure with foam strip or some such, to allow for expansion, and there’s a great opportunity for underfloor heating in the screed as part of a journey to an air source boiler replacement. There’s merit to it, particularly if it’s a whole house being refurbished, and yes, I’d be keen to learn what the BCO would say too. They may suggest using ballast or type 1 compacted in layers rather than sand all the way, but probably fine as it would meet the regulations.

[@tomasrazgus7331]

Don't you need to add hydroisolation underneath those foam boards?

[@SteveWardellDIY]

Provided there is good airflow underneath, and a good damp proof membrane segregating timbers from damp supporting structures, no, I don’t believe you do Tomas. It wouldn’t harm to though, if you have some and the time to apply it.

[@tomasrazgus7331]

@@SteveWardellDIY Thanks. Addition question. How to protect those boards from mice or whatever it could be?

[@SteveWardellDIY]

@@tomasrazgus7331 The air bricks in the walls of our home have small gaps, big enough for insects but not mice. The only time we ever had mice under there was when I was rebuilding the linked utility room. Little blighters took the opportunity to set up camp. Humane traps caught them and I let them out a couple of miles away

[@PoohBear01]

Any difference with the stove now youve sealed up air draffs?

[@SteveWardellDIY]

Hi Poohbear. The stove had no requirement for an external vent, so I expected and hoped sealing the floor would not change anything. There’s no noticeable difference to the stove working, though the room gets warmer than it ever did before, even with the door open.

[@PoohBear01]

@@SteveWardellDIY Thats good to hear as Im the same with no vent requirement but looking to do the same soon.

[@SteveWardellDIY]

@@PoohBear01 I checked the gas use for the house for November this year vs November last year. It’s 20% less this year. We may have had a comparatively warm month but I’m hopeful it’s a trend due to the insulation. Time will tell.

[@phosmathena6433]

Thank you. Is it a dirt foundation or cement? What do you recommend? House over 100 years old. Foundation is dirt and not sure of pipes. Thsnk you

[@SteveWardellDIY]

Hi there. The subfloor is dirt in this property. So long as you ventilate the sub floor properly, with air bricks at each end, I hope you would find this insulation method works for you. I don’t know where your pipes are. You’d need to find out.

[@myabcpilates8783]

Great video

[@krishchaddha1651]

could you have used gapotape to get a better fit? instead or as well and top tape?

[@SteveWardellDIY]

Hi Krish, I’m not sure what gapotape is. Aluminium foil tape is recommended by Celotex to create a continuous foil membrane, so that’s what I use.

[@krishchaddha1651]

@@SteveWardellDIY kzbin.info/www/bejne/hZ7OZ2uQYtl4bbc

[@SteveWardellDIY]

That’s a really interesting video Krish. The shapes and sizes of existing builds are not as accurate as the standard frequency in the new build, so there’s no way of mass cutting and using Gapotape to make up the differences. The pieces I had to cut were all one offs, and were accurate with very small gaps. The insulation capability would not be reduced by any amount of note by small gaps that are sealed to prevent airflow through them.

[@StickyBrickit]

Did you consider using a vapour barrier as well?

[@SteveWardellDIY]

Absolutely yes, and I discovered the continuous foil upper surface with foil tape bridging the joists provides a vapour control layer. Thanks for watching. Steve

[@pcatful]

Was there no crawl space? I think I would have crawled under with fiberglass batts and shove them up between the joists, Instead of tearing the whold floor up and cutting each insulation board one at time. Or maybe just insulate and line the crawl space. It doesn't look like you have crawl space ventilation anyway, so how big a deal is the all the air sealing which could be taken care of with an underlayment when you lay the hardwood.

[@SteveWardellDIY]

Hi Peter, there’s about 300mm - 500mm depth of crawl space across the room, and it’s ventilated from outside via air bricks. I cleared the air bricks to make sure they work for the future, and airflow is absolutely needed to keep the subfloor moisture level low enough. Installing fibreglass batts is an option I’ve used in a previous house, but has a lower insulation value and does not prevent airflow, so is no where near as effective. Solid PIB is a better solution.

[@mikgsal1384]

Excellent job thank you. Since this is a diy solid floor insulation will you be able to reduce your EPC rating by doing this?

[@SteveWardellDIY]

Hi Mik, yes I think it will contribute to the EPC, so long as you can evidence it’s there, so best take some photos. Check with your local EPC surveyor. They’re named on the web

[@telosfd]

Wonderful! I like this kind of job.

[@SteveWardellDIY]

Thanks 😊

[@tincanpete]

Helpful video, thanks!

[@erlwindegans3954]

Why reuse the floor boards and not stick chipboard down if you carpet over it anyway? Not a critic, just a question

[@_Damian_.]

Why waste money buying new chipboard flooring when the floorboards are still good?

[@erlwindegans3954]

@@_Damian_. mlre solid and less squeaky but that is my opinion 😂

[@_Damian_.]

@@erlwindegans3954 ... if you have the spare cash I suppose which a lot of people are struggling with at the moment, oh and don't forget the hassle of getting rid of 12m2 of old floorboards. As for squeaky boards, I'm sure he said he screwed them down, squeaks will be eliminated that way.

[@SteveWardellDIY]

Aside from the cost, I’m a Womble and a restorer, so prefer to reuse the old boards if they’re in good condition. They are as strong as chip board and when screwed down do not move or squeak. Easier to relift if there’s ever any subfloor issues too.

[@Anakinuk007]

Chipboard is cheap and cheerful. If you have good solid floorboards like these, you’d be mad to cast them off! Realistically with chipboard you aren’t going to/cannot make every single board end on a joist, which means over time those unsupported joints will creak, flex and bend. Floorboards are usually solid bits of timber and they are fitted over joists with no unsupported areas.

[@daithibailey]

Thinking of doing this myself at some stage, I was wondering though - why use silicone instead of expanding foam?

[@SteveWardellDIY]

I’ve not done much work with expanding foam. Could be a good alternative. I like a tight fit on the boards and silicone works okay if you achieve this.

[@huwtindall7096]

Is there a standard width between joists in the UK? If so I imagine you could also get insulation pre-cut to that width and save a lot of faff!

[@queeg6473]

Not in old houses.

[@SteveWardellDIY]

Not in 1915 when the house was built, but there was nothing stopping me reinstalling them at regular intervals. It’s a good suggestion 😊

[@rob19632]

Most joists are at 16inches very similar to modern 400mm. As a sparky I have taken up an awful lot of floorboards. Up north nearly every floor is tongue and grooved so much harder to take up.

[@SteveWardellDIY]

@@rob19632 I think you’re right. 16” seems pretty standard in most homes I’ve worked in. They were closer in the rooms in the video, nearer 14”, but with variance too.

[@richardgore2000]

The celotex was a snug fit, as required. But what if you screw the batons, that the celotex sat on, under the joists at right angles. The celotex then lay on a few batons to hold it up. I'm thinking less batons would be needed? Great video though.

[@SteveWardellDIY]

They wouldn’t seal the gaps though that way.

[@dee106ful]

Go easy boy you will definitely split these old boards. Take your time don't lever force but apply pressure equally. Must remember modern boards are not the correct size you may need to go to salvage yards.

[@richard.j]

Thanks for the video - did you consider rock wool instead with membrane over ( celotex - )fire resistance

[@SteveWardellDIY]

Yes Richard. The thermal loss capability of rock wool is much poorer than insulation board. You’d need twice the thickness or more to achieve the same insulation, which would have been harder to install.

[@richard.j]

@@SteveWardellDIY thanks Steve -understand thermal performance ( post green fell - wouldn’t specify a phenolic foam.)

[@SteveWardellDIY]

@@richard.j for me, and most in fire safety, that choice is based on risk assessment and compliance. In this case the flammable material is contained in an environment where ignition sources are low and highly controlled, and the house has good smoke detection, as all homes should. For the safety of my family and myself I’m satisfied the risk is controlled.

[@mr.wizeguy8995]

Would be better to cut them inch narrow than gap and use elastic spray foam around and all board seams.

[@SteveWardellDIY]

Better insulation? I’m not sure Wizeguy. Might be a messier job using spray foam. Give it a go and let us know.

[@mr.wizeguy8995]

@@SteveWardellDIY I'm sure i have done many just last week did roof insulation with similar board. You method isn't air tight it leaves tiny caps all over board. And when there is air leaks there might happen condensation and that leads to rot. Here is example video not mine but you get point. They also does roof and walls kzbin.info/www/bejne/kJi0faF6nrB3ntk

[@SteveWardellDIY]

@@mr.wizeguy8995 Rest assured are no open air gaps when following the method I’ve shown. Any tiny clearance gaps are sealed by the battens below, the foil tape above, and the three lines of silicone to the brickwork around the perimeter. Thanks for your feedback.

[@prodical666]

Could another method be to run your batons perpendicular to the joists every few feet, underneath, instead of parallel. This way you would save a lot of time, a lot of wood and you could get thicker insulation boards. Presumably as thick as the joist itself?

[@SteveWardellDIY]

Yes, you could go for that approach. I chose not to because preventing air gaps and air flow is critical. The battens beneath the joist/board joints help create an air seal.

[@prodical666]

@@SteveWardellDIY Yes good point, the batons running parallel would have more contact therefore more sealed. Food for thought as I am planning on doing this in near future.

[@riz_1ne]

Can you tell me if the wood battens you used to support the insulation are normal untreated strip wood or do you have to buy treated battens ?

[@SteveWardellDIY]

Hiya. The battens were treated roofing battens. The sub floor moisture content will be similar to outdoors, so good practice to use treated. Also, untreated battens may not be so readily available in the UK, as they are generally supplied for the roofing market where they must be treated.

[@riz_1ne]

@@SteveWardellDIY thanks for getting back to me, would you no what size your battens were exactly and where did you buy them from as I’m having a hard time finding treated battens with small measurements

[@SteveWardellDIY]

@@riz_1ne they were from our local builders’ merchant Parkers. I can’t recall the size.

[@aali4276]

Great job

[@TheNorthernmunky]

Great job mate.

[@SteveWardellDIY]

Thanks Logan. 😊

[@josephbohme7917]

do a standard in each bay and use a Spray in foam for the gaps if you have a 1" interor gap it is better than a single layer thcker foam and is free insulation!! these joint could even have 1/2" shheta blow ao the beams are fully insulated - no bridging. Better to cut narrow- move it elseswhere before you shave it.

[@SteveWardellDIY]

Hmm, not sure I agree with your 1” air gap theory Joseph, I’d have to look into it .

[@thebakers9403]

Great job & excellent advise - just about to embark upon a similar job.

[@jimirons833]

Beautiful job 🫡

[@alanupcraft2758]

Would this bee a good idea between the roof rafters.

[@SteveWardellDIY]

Yes Alan. Leave a 50mm gap above the board for air circulation. 150mm total is the current building regs requirement (I think) which can be achieved with 75mm between, for 125mm roof joists, and a further 75mm beneath the joists held in place by battens or plasterboard directly.

[@kevinkellaghan3888]

@@SteveWardellDIY This air circulation will also depend on the felt membrane in use in the roof i.e. breathable (modern roof roofs) or non-breathable (older properties). With older properties you will need the addition of roof vents (eaves and ridge) for crossflow air circulation. Just experienced this myself recently. Plan on doing this in the floors downstairs in my house, was wondering about air circulation but you seem confident it won't be an issue and I tend to agree with you. Thanks, great detailed video.

[@smellypunks]

Good work Steve. So the house was build in the 1920s?

[@SteveWardellDIY]

Slightly earlier, but yes, around then.

[@BruceLethal]

Is there any risk to moisture being trapped between the kingspan and floorboards? Also would be keen to see how noticeable the change is . Thanks

[@SteveWardellDIY]

I think not. Condensation builds by warm air hitting cold surfaces. There are no cold surfaces as the insulation as a temperature gradient through it

[@SteveWardellDIY]

I’ve not measured the fuel saving. Only time will tell, but it feels warmer in the room. With the log burner running it gets too hot, where it didn’t before

[@BruceLethal]

@@SteveWardellDIY awesome that makes sense

[@fabriglas]

Does this material off had or smell as my nose is very sensitive.... It would annoy me terribly if it did.

[@fabriglas]

Off gas , predictive text sucks

[@SteveWardellDIY]

Hi fabriglas. It’s a Celotex product I used. It has a smell that’s a bit fishy when cut, but none at all when installed and it’s completely sealed from the room by a foil layer when complete so even if it were to smell over time you wouldn’t smell it.

[@AlexeiTetenov]

I'm surprised that there is no thick plastic to seal unwanted moisture from the dirt floor.

[@SteveWardellDIY]

I installed a DPC under the dwarf walls of the kitchen as I was rebuilding them, but normally in these types of houses the dirt floor is open to the sun floor void and the moisture kept in check by the air bricks delivering a continuous flow of fresh air. I cleared the air bricks as part of the job, as they were partly blocked.

[@Game0verFool]

A reciprocating saw works a treat to cut the nails of any floorboards stuck under the skirting 👍

[@SteveWardellDIY]

Great idea. Tricky doing it safely though.

[@marksecker1596]

Well done.

[@LabRat6619]

Why did you start in the middle of the floor, I was taught to start at threshold or where someone has cut before. Also, if you were laying carpet, why didn't you use ply to refloor your room?

[@SteveWardellDIY]

I don’t know if it would have been easier starting anywhere in particular. Maybe doing the middle first made it less likely I’d fall through 😀 Ply costs money and the old boards were fine. Reusing materials is more sustainable too.

[@georgeroberts6457]

great video i do have to say using a sharp knife to cut is not the path i would have gone down at a minimum a hand saw is a must

[@SteveWardellDIY]

Thanks for watching George. There are some new serrated knives and battery operated fine toothed saws on the market that would make a more accurate perpendicular job of it. I like using a knife as the dust produced is minimal. Using a saw means vacuum extraction or a dust mask.

[@inmadmads3755]

his brilliant.. Instead of the baton, I would use Expamet Steel Angle bead.

[@SteveWardellDIY]

Interesting alternative Inmad. Would that be cheaper?

[@davidaitken952]

Using a carving knife one handed whilst cutting towards your other arm whilst balancing on two beams?? Take your work outside to cut in a flat open space with the correct tool and live longer. Whilst you had the boards up I would have placed a dpm on the foundation for a little bit extra protection from moisture ingress through the slab.

[@SteveWardellDIY]

Thanks for your tips David. The DPM is an interesting one. Difficult to use a carving knife two handed, and if it’s sharp it shouldn’t need two handed levels of force. Space wasn’t an issue, and the knife was controlled okay. I’m happy with the risk assessment but always encourage others to do their own.

[@JohnnyMotel99]

In reality, cold air sinks and hot air rises. So a just as effective method would be rockwall batts, insulate and draught proofing.

[@SteveWardellDIY]

I suspect airflow, due to air pushed into the subfloor from outside and warm air rising up chimneys and out other ways, may cause air transition through the floor boundary to play a big part in poor building thermodynamics. Simple warm air rises and cold air falls logic may not accurately apply, and stopping airflow through this critical boundary may be a really important factor.

[@JohnnyMotel99]

@@SteveWardellDIY Totally agree about air leaking through the old floor via the airbricks. I made the comment about rockwall batts, because my brother has an old victorian house with a very similar situation on the ground floor. He put in batts between the joists and it made a massive difference to their bills.

[@andrewspence5642]

what carpet underlay did you use?

[@SteveWardellDIY]

Hi Andrew, I used Carpet Right’s most expensive rubber one. Probably got ripped off but it’s lovely. I’ve since spotted some 12mm thick wool underlay online that may be a pretty good cheaper option. I’m not an expert on this, though I do fit all my own carpets to make sure it’s a good job

[@kevocos]

Good video but I definitely would not have used foil backed PIR in this instance. The insulation needs to be breathable and ideally hydroscoptic. Using PIR runs a high risk of holding dampness against the joists and especially so at the joist ending, and if that occurs that becomes a major problem.

[@SteveWardellDIY]

I’m unsure where you think the moisture would come from @kevocos, as the subfloor is ventilated and the foiled internal side provides a vapour barrier preventing a dew point further down. If a hygroscopic insulation were used instead it would absorb moisture and risk transferring it to the timber, causing the problem you’re concerned about.

[@simonstv923]

What a fantastic guide - Thanks so much for doing this Steve. How long did it take? All done in a day?

[@SteveWardellDIY]

Hi Simon. Installing the battens and insulation was done over a couple of days, but there were other jobs such as replacing rotten timbers and clearing air bricks that extended the job. The other time lapse video on this subject was 9 hours, to install insulation to a prepared space 12 sq m

[@briansteer8209]

Looks like it needs a good rewire before you put insulation everywhere

[@SteveWardellDIY]

Yes indeed Brian, the whole house needed a rewire when we moved in. It’s been done as part of the insulation project where not already completed.

[@tobybarker6808]

I'd have used foam to seal, but thats cos I love foam!

[@pumpkinhead456]

It's great that people have a shot, but probably shouldn't post them as instructional videos. There are ways to have done this quicker and better, and with more info (like which screws to use, why screw and not hammer etc). I'm sure it will be beautifully warm however!

[@SteveWardellDIY]

Bit odd suggesting people shouldn’t post videos pumpkinhead. As you can see from the comment, lots of viewers have found useful tips and guidance from it. It’s always possible to improve of course, though I doubt I’ll redo this one. Do suggest how to do it quicker and better please, and the type of fixings you think are best, and the community will benefit from your insight.

[@pumpkinhead456]

@@welldoneboysgoodprocess step 1, label all your floor boards. An easy way is to do top to bottom in letters, left to right in numbers. That'll make it much quicker to put them back down. If you are screwing the boards down, use a screw like Space Wirox that has the double thread, if you are leaving the boards exposed use a cut clasp nail. Best pilot drilling the holes at the ends of boards, no need for mid boards. If you have to use PIR I'd recommend gapotape for a proper seal, I'd really encourage a natural insulation however like Steicoflex - no need for a vapor barrier with it. The Restoration Couple and Gosforth Handyman both have good videos worth watching.

[@pumpkinhead456]

@@SteveWardellDIY I love people posting videos, I was just saying it's more of a video of how you have done it rather than how and why it should be done a certain way.

[@pumpkinhead456]

@@welldoneboysgoodprocess it would be a waste of cash between floors, you could use sound proofing rock wool for noise purposes but no need for insulating. Internal wall insulation is a good bet and worth doing well, worth doing some research!

[@SteveWardellDIY]

@@pumpkinhead456 agreed, no point between floors unless the room below is kept a lot cooler/unheated, such as a garage.

[@Daisy-wy5mn]

Wish I’d insulate my floor before I tiled it 🫣

[@Binbag1010]

Clout nails ? they are cut clasp nails.

[@SteveWardellDIY]

Yes! Cut clasp. That’s the ones. Used by victorians and edwardians alike.

[@HaroldBarrett]

I have to do all this 😩

[@SteveWardellDIY]

Hi Harold. You could always buy a new house instead 😁

[@irenebignall7245]

Personally I would of made an hole and gone underneath and cut the kingspans to fit between the rafters

[@SteveWardellDIY]

Hi Irene, I’m unsure what you mean. I could get though the joists to beneath, but didn’t really need to much, and the insulation is cut to fit between the joists. Help me understand 😂

[@irenebignall7245]

@@SteveWardellDIY i replied earlier into your video,then realised you didn't have much room to get underneath to fix in the insulation,and also it was a bit trickier to maneuver around the pipework,so yes you did it the best way and it was thoughally enjoyable

[@SteveWardellDIY]

@@irenebignall7245 that makes sense, thanks for writing back.

[@Pete.Ty1]

👍👍👍

[@craiggreenhalgh1082]

Thank God I've Got Solid Floors In My 1930's House .😂🤣😎👍

[@SteveWardellDIY]

😂

[@hewoguys2506]

one thing i must say how u spend all money on good insulation level a decent tape measure but dont buy a saw 😅😅 make no sense

[@SteveWardellDIY]

Thanks for watching Hew, and for your feedback. Using a saw creates dust and I wanted to avoid this. The knife is a steady and reliable way of cutting dust free, but takes practice to use accurately. It’s tricky on thicker sheets and probably best avoided on anything thicker than 75mm. If I were to do another project with large volumes of insulation I would invest in a fine toothed reciprocating saw and guide. There are some good products out there.

[@hewoguys2506]

u should of used a foam gun on edges

[@SteveWardellDIY]

Actually Hew, having seen the product at a trade show, I’ll be using Gapotape in the future.

[@jayg7889]

I hope you let your Mrs carve the Xmas Turkey.

[@SteveWardellDIY]

You’ve hit on something there Jay. Mrs Wardell would have made a much neater job of it.

[@nigelsmith1198]

Painstakingly slow.! I’ve just completed 100m2 and cut that with a skillsaw and dust extraction.! Far quicker

[@SteveWardellDIY]

Sounds like a great option Nigel.

[@michaelfraser5723]

No sign of death watch beetles

[@SteveWardellDIY]

No none Micheal. I’ve found lots of rotten joists but no beetles or evidence of them