Garden Room Workshop: Part 15. Wall Insulation & Vapour Barrier

[@simonjarvis7362]

For cutting PIR there are purpose made handsaws for the job and they create MUCH less dust. They have a cutting profile similar to a large breadknife. They can 'wander' a bit though on thicker stuff 50mm plus. However if you want to make your life really easy you can buy 150mm jigsaw blades with the same 'breadknife' profile. These do a fantastic job, even in thick PIR. Very quick and low on dust.

[@AliDymock]

Love it. I wonder if they make circular saw blades for the task too...

[@simonjarvis7362]

@@AliDymock Hi Ali, yes they do, my apologies, I should have included that. Look for a circular blade called 'Centrefire" by Bullet Tools. American brand but available on Amazon UK. I have only used the handsaw from Bahco and the special jigsaw blades from Bosch.

[@AliDymock]

Super, I'll pin your comment to the top for others to see 👍

[@garyr1522]

And the fact that you have pinned the above (as it;s clearly a top tip, however amazing a Festool mini chain saw thing would be) is further evidence of your ludicrous helpfulness! @@AliDymock

[@stancullen2408]

I cut pir with a knife then like plasterboard snap over and cut other side very quick easy method

[@bobwhite8638]

Next time you want to cut the foam, use a electric carving knife like the ones used to carve a turkey. Clean cut, no dust, quick cuts and no beads. No wasted material by having blade cutting a curf through the material.

[@onnozweers]

I've seen lots of videos on DIY building, renovation and insulation, but none as crammed full with knowledge and tips as yours. Thanks!

[@AliDymock]

Thanks Onno, I appreciate that!

[@DM-qd5yr]

the clarity and attention to/ level of detail...love this series.

[@tomnorth783]

Absolutely fantastic video. I’ve learnt so much in this video. I never knew that the vapour barrier goes on the warm side of the room, so you wouldn’t do, vapour onto brick then batten then pir. You would go, batten on brick first, then pir in between, then Vapor barrier. Such a brilliant video. This guy is fantastic. So classy and always happy to learn and teach and help along the way to the viewers. Thankyou for this video. Tom.

[@rubiconexotic8753]

I’ve never seen plastic sheeting put up over the joists internally before plaster boarding. If you’ve got Tyvec on the outside I’m worried you’re trapping moisture inside the walls (timber) which can lead to rot. I wouldn’t be surprised if your walls start to sweat when it gets hot. I’m pretty sure PIR insulation does that job already. Correct me if I’m wrong

[@bucketandspade]

This is exactly what I'm thinking...I'm currently part way through my build, and logic tells me wrapping the inside like this is not good. Different states in America, moving north into cold regions, it makes more sense, but in the UK, this can't be right.

[@ThisDesignedThat]

In the process of building my own shed and have been researching this a lot. From my understanding: - Tyvek outer wrap is a BREATHER MEMBRANE. It lets moisture pass through it on one side but does not let 'bulk water and air penetrate it. - The vapour barrier on the inside of the walls is to stop vapour from the inside of the building passing through the walls and hitting the cold side of the insulation and condensing.

[@stimuli9443]

Thanks for taking the effort to share what you learned, and explain everything in thorough detail. I really appreciate that you don't treat your viewer like an idiot, while also not making assumptions about what they might already know.

[@AliDymock]

So glad you like it. That's right, nothing is dumbed down but nothing is left out either :)

[@eamonholden8083]

Brilliant detail and step by step nothing missing, been looking at a project to convert my old garage into a useable space. This will help me immensely thank you, by far the best instructions love the use of the diagrams to explain certain aspects of the build.

[@LikeDesignHero]

Thanks for taking the time to make this video Ali, all the blog articles you read are SEO generated garbage that don't actually go into the details or realities of building this DIY. yours is really definitive

[@CraveThatCoin]

Needing to know which vapour barrier to get, come back to your video and there it is right in the description. Thanks a lot!

[@iangodbehere19]

Insulating a concrete garage, this video series is awesome, thanks so much

[@davewheeler6027]

I am insulating a single skin room attached to the back of the house. Did you leave a gap between the studwork and the wall or go flush?

[@ThousandJourneys]

Thanks for continuing with this series ... it's invaluable help for me, and I'm sure many other people too.

[@hipdogdsv]

So many questions answered via your videos. Im about to convert a 14 x 40 shed with lofted ceiling into a tiny house.

[@MrGlenfraser]

I'm just about to add an upper floor extension on the house in timber as the brick cavity wall is too small so will be using some of these tips....

[@garyr1522]

Others have said as much already but still feel compelled to say what a fantastic series this is: literally perfect balance of detail and getting on with it. Top job Ali, seriously good videos (from sunny, in isolation, Wrington, Bristol).

[@AliDymock]

Thanks so much Gary, it helps to know they are hitting the right cord so thanks for taking the time to comment!

[@GeekStreet]

Had this pop up on my feed, great video and good attention to detail. This is the thing about doing it yourself you can take your time and avoid cutting corners also a good help when getting builders in as gives you reference point to compare with!

[@AliDymock]

Spot on. Even knowing a bit about this stuff can help you identify cowboy builders.

[@pulporock]

I’ve made that exact statement, no one is more interested in your build than you. Excellent vid, well explain, and shown. Cheers

[@AliDymock]

Great minds 😉

[@2wheelspy]

Finally. Thanks for uploading Ali, I’m sure I’m not the only one been checking for your next video.

[@MrJohnnynapalm7]

Lots of top tips, a bit of Festool action and DQ Quads (I think) - what a great combination! 👌👍

[@caskwith]

Great to see another video. FWIW standard plasterboard is a perfectly good vapour barrier on it's own (once painted) if you install it properly. Of course a polythene sheet behind it is extra insurance and doesn't hurt but isn't strictly necessary.

[@AliDymock]

really? Hmmmm. So does the paint act as a vapour barrier or the plasterboard or together? And is this the case if you don't do a full plaster skim and just tape and joint (drywalling)?

[@caskwith]

@@AliDymock It's the combination. The bare plasterboard provides most of the resistance and then you cover it in paint which is like sealing it up. The vast majority of top floor ceilings in houses are built like this, plasterboard on the ceiling and then above it is unfaced fibreglass insulation. Works just fine on ceilings like that.

[@tuurkishman]

Great job mate, lots of good ideas to get me going

[@Chrismartin88]

Cut Your installation to the correct size of gap then cut out any grooves needed for pipework and electricity cables but cover the back of the insulation where the cut is with silver tape folded into all the crevices and gaps before placing over the electrics or pipework

[@M00seL00seAb00tH0use]

Great to see you back. I hope its all going well in the new house.

[@blueangelstudios]

+Have been waiting a while for the next installment. Best series on how to build a garden room. Awesome.

[@AliDymock]

Thanks Chris!

[@robinlaker]

This series has been brilliant! I’m just starting a timber frame conservatory build on the side of my Mum’s annex. There’s a covered decking there already but, after watching your videos and doing some research, I’ve realised it hasn’t been built properly. I’m essentially starting from scratch. I’m a self employed mechanic/car builder/restorer by trade and a keen DIYer - after the eye-opening and stressful experience we had with the builders who worked on the annex I’m doing stuff myself.

[@AliDymock]

That's awesome, good for you. I must say, it's nice to have control so good choice and once you break the stages down, you realise it's very doable! Best of luck, with your experience you'll do great. Feel free to send photos Robin, I always learn from them 👍

[@robinlaker]

Ali Dymock thank you for the encouragement! I work from home and I’m extending my workshop bit by bit as well. This will be my first venture into a domestic build and I’m really looking forward to it. I’ll definitely document the build and keep you posted 👍🏻

[@robinlaker]

Ali Dymock I’ve just ordered the materials for the framework so, providing COV19 doesn’t disrupt delivery in the next few days, I’ll be good to start next week. One thing I wanted to ask (I’m sure you’ve covered the topic somewhere and have been asked before) - did you look into putting a breathable membrane under the floor insulation over the joists? Tyvek suggest you use Supro in a suspended floor but that’s with a wool/glass quilt or batt insulation. Quinntherm’s installation guide is as per you’ve done. My only thought was could moisture in the air from underneath get into the floor joists and soak into the sides of the PIR and not be able to get out? Perhaps I’m massively overthinking this but I’d really appreciate another person’s perspective on this. One idea I had was to staple dpc to the top and sides of the floor joists to form a barrier between where the timber and the PIR meet...

[@AliDymock]

@@robinlaker I haven't covered it again but will do so, though no quite the question you ask. The floor and insulation should be open to the underside to allow air flow. It's trapped air that is the problem and why houses have air bricks to allow that flow of air under the floor. A breathable membrane isn't really required because it stops rain water (mainly) which you won't get underneath your garden room. You could use it but I'm not sure it would do a lot. Not quite sure what you mean in the last sentence (I can't picture it) but I really think it's not needed and could actually cause problems. Do you have a link to Quinntherm's installation guide? I'd be interested to see/use for a future vid.

[@robinlaker]

Ali Dymock that all makes sense. There’s a lot of online info and it’s difficult to know what to go with sometimes. www.quinn-buildingproducts.com/insulation-boards/floor-insulation/insulating-suspended-timber-floors-between-timber-joists/ - hopefully that link works?... 👍🏻

[@MarcDymock]

Excellent work Ali 👏

[@paulround8501]

You don't need to worry about insulating around cabling as your electrician will already have derated the cable to take insulation into account. Derating essentially means taking the maximum current rating of a given thickness of wire and reducing it by a factor based on what it is going to be surrounded by. In stud walls this typically always accounts for the wall filled with insulation.

[@tionanima]

I've never seen a channel with 36k subs but 300k views per vid. Congrats

[@AliDymock]

I guess it could be turned around: I've got all these views but not many subscribers 😰😉

[@nickb7040]

BTW to cut insulation I got some 150mm long insulation jigsaw saw blades from milwaukee, cuts like butter and virtually no dust as its more like a knife and not a cutter. U also can do angle cuts well too by using the angle on the jigsaw.

[@AliDymock]

Sounds brilliant. I'll do the same in future for sure!

[@stiffrock3036]

been watching 👀 from the first episode thought i would watch how you built yours as i was just starting mine and was looking and learning how and where to start its been a massive learning curve doing it all myself .. after watching all your videos and a few others built up the confidence i just went for it turned out pretty good 😉 i went for concrete base, shiplap cladding, wool insulation, plasterboard then plaster, rubber roof, tiled floor, with underfloor heating, 😅😅 with a shower room with toilet, total size 3.8m x 7m

[@AliDymock]

Wow, with underfloor heating too, sounds grand - do you have pics?

[@stiffrock3036]

I Documented it with pictures and videos but my phone got stolen so lost most off the project will upload the ones I have plus ones off it finished

[@AliDymock]

That sucks! sorry to hear that. Well if you fancy having it on the website regardless, pop me an email: www.alidymock.com

[@mariah4451]

Excellent to see you back Ali. I'm starting to plan a workshop build for this summer and your videos are all I will need to guide me along the way. I'm so grateful to you for taking the time to share your beyond generously comprehensive 'how to' advice and seriously detailed research into all areas of your build and your great camera work too 😃👍 I hope all is going well with your new home alterations 😃😃

[@AliDymock]

Thanks Maria. Great, can't wait to see yours!

[@mariah4451]

@@AliDymock 😃👍

[@AliDymock]

Hey Maria! I couldn't help but notice you didn't comment on my latest video and you ALWAYS COMMENT! so I wanted to reach out and make sure you're okay?

[@mariah4451]

@@AliDymock What a lovely thing to do Ali, thanks so much. I'm great thanks. I don't know what's happened there, that I've missed one of your videos 😕 I will catch up immediately 😃😃 I hope you are both well and keeping nicely busy 😊 Take care and stay safe 🌼

[@AliDymock]

​@@mariah4451 glad to hear it! :)

[@Bozzerrrr]

Absolutely excellent series sir! I was enthralled. I’m only thinking of building a summerhouse, nothing on the scale of your build, but found myself binge watching your build rather than what I probably should have been watching/researching😂 Its great to see somebody putting so much effort into a project and, at the same time, so much effort into passing info onto others. Keep up the good work with projects at the new place. Thanks and Bravo!

[@AliDymock]

Thanks! Sorry to have stolen your evening! Best of luck with your summerhouse!

[@opumfrey7625]

I can’t tell you how good these videos are! Keep them coming!

[@AliDymock]

Thanks for encouragement Oliver, it's appreciated!

[@alasdairmackenzie515]

Welcome back, Ali! Hope the move up-country went/is going well.

[@newlinkdirect]

Ali +1 great series, love that you explain the thinking... so good. I'm going to do my own.. and your series is a big plus.

[@neilsomers5644]

Ali, another great video. I really look forward to your videos as I am planning my own garden room to start this summer. I hope all is going well with the new house and thanks again for continuing this series

[@AliDymock]

Thanks for your support Neil, it means a lot :) I will be getting the next few out more quickly but will be about a month before the next one

[@roberthardy2013]

I use the aluminium tape for lotsofthingsand it sticks really well, BUT it has virtually no mechanical strength in tearing mode etc. I would have used this to seal then Gorilla duct tape on top for strength, this stuff is really strong and also sticks well.

[@ranjitpatel496]

You sir are amazing taking your time with making this video, it will help me greatly with my outdoor office.

[@AliDymock]

Glad it was helpful Ranjit!

[@Chad-ski]

I was looking at insulation between my roof rafters in my loft. I didn’t have a clue but a lot of things explained 😁

[@ABell676]

Can’t wait to see the projects on the new house.

[@AliDymock]

me too! We're saving at the moment lol

[@ABell676]

Ali Dymock I bet 😂 Tip for someone who’s been there. Try to do one room at a time. It’s tough but worth it.

[@AliDymock]

Absolutely - definitely the best way to go, I'd go potty otherwise. Doesn't always pan out like that as it turns out:. The downstairs shower room could really do with being upgraded from a 6mm to 10mm cable for the electric shower. That means I need to take the plasterboard off the hallway to make way for the wire. As I'm doing that we may as well put spotlights in the hall ceiling. Since I'm doing lights I should probably get the ones in the utility/boot room done too. Oh and yeh, I need a new consumer unit with RCD protection to stop us getting electrocuted in the shower 🙈🙈🙈😭😭😭

[@ABell676]

Ali Dymock 😂 tell me about it. I changed a radiator to a triple column cast iron in the sitting room and ended up changing all the flooring, fixtures, making fitted cabinets in alcoves etc. It never ends 😆

[@robertthompson1993]

Very helpful. Will be watching the rest. Thanks for sharing.

[@Pawel-s3i]

This summer I’m gone build exactly one like yours, thank you for all instructions... well done 👍🏻

[@rss112]

Great video, currently converting the garage into a living space. The insulation part really helped as the builder is trying to do it on the cheap!

[@tonym992]

Great advice and well explained. Thank you.

[@antgaunt]

This couldn't have come at a better time! thank you so much! :) And thanks for the rubber roof code too!

[@andreycham4797]

you put OSB on outside of the walls, if vapor find a way to get in walls it will never dry out of there than you should have left small gap between insulation and plasterboard to let foil to reflect heat back in the building

[@AliDymock]

2 good points of discussion! 1. The OSB is somewhat breathable so will let moisture out. Also there are small gaps between the OSB so it should be fine. You can go without OSB or ply on the walls but the walls won't be as sturdy - there are always pros and cons of course. 2. True, you need around 50cm gap for the foil to radiate heat back so that would have left about 40mm to fill with insulation. Which is likely to be better?: 40mm insulation reflecting heat or 90mm insulation. My bet is on the latter, but again - pros and cons.

[@anonymous_bot_bot]

Ahhh... more videos! Keep them coming.. I may just overtake you and used your vids as inspiration and direction so far.

[@lapinchiloca]

thanks for the info, I'll be doing a similar job next week for the little one's room 👍

[@AndrewHelgeCox]

09:50 Anyone who copies your warm roof should definitely not add any insulation under the joists. That would pull the dew point down and risk lowering it as far as your lower deck / top of your joists.

[@AliDymock]

Agreed, only for cold roofs

[@RickGrimes807]

True👍

[@bwisternoff8986]

Keep it up mate. Loving these vids x

[@kolgrillarn]

Leave 1cm on every side and fill it up with sprayfoam. Much easier, locking the insulation and airtight> warmer👍

[@keendnb]

Festool are the nuts, I borrowed a friends when over boarding my wife's salon for the tiled floor..... Made light work of it

[@vikingofengland]

As ever a great video. I am about to start wall and ceiling insulation (I have a cold roof) so this has answered a few questions I had.

[@AliDymock]

Glad to hear it Justin 👍

[@Terrythemaker]

I’m so glad I watched this video as I’m just about to insulate my double brick built garage and was going to put the vapour barrier on the wall side of my studding, as I had seen this on another well known video maker. Great detailed video 👍🏼

[@gman1087]

Good morning Ali ...nice to see your next instalment....looks like ur nearly there!.....hows things going with ur new home....do keep us up dated old bean !

[@AliDymock]

haha I will. We really haven't done much and have kept to the 6 month rule of no works and new ideas and thoughts have come to mind but this year should have a few interesting projects. This series is the priority though, otherwise I'd annoy everyone I think lol

[@MadsFeierskov]

I really hope to get started on mine garden room next year and this series have given me confidence that I won't encounter pitfalls that I can't manage on my own. I just discovered posi-joists, so I want to look into making a warm roof that's not as tall, if that's at all possible. Unfortunately pir foam insulation seems to be pretty rare in Denmark, so I'm worried it might be too expensive to consider. Seems to be nice to work with, especially for floor and roof.

[@AliDymock]

Good stuff. Get the base/floor right and the rest will fall into place. Posi-joists look great especially if you have a really wide span (6m+)! Best of luck with your build!

[@kyehunter1855]

This is such help with the garden room I’m now building just would help if they came out a bit quicker so won’t need to wait till next video to come out but still such help

[@AliDymock]

Glad they are helping Kye. Heheh I know, I'll do my best to get them out quicker.

[@archangel6415]

Just use a bacofoil roll and slice accordingly. Use a spray adhesive and apply or, a spray bottle with slightly thinned PVA. Well worth considering. I’d use 1000 gage polythene, especially on a small are where it’s less expensive

[@bucketandspade]

This bacofoil trick could well be genius

[@mattbailey818]

Carcassing timber dimensions generally seem to be less than their stated size when regularised. How do you get round this for insulation - for example 100mm insulation for 100mmm joists when the joists are more like 95mm. If you go for a 90mm insulation Does the gap between the insulation board and the full width of the joist matter?

[@AliDymock]

I went for 90mm and no a little gap between insulation and plasterboard is fine

[@MrDazthaman]

Solid content pal, new sub earned.

[@beefyu.k.1600]

I’m on part 15 👍 very well presented watched them straight through on the tv so not seen the comments. setup is slightly different for KZbin on the tv Awaiting this weather to break and starting mine 4x4,foundations in ready. All I’ve done is watch the videos is there a point in a price has been established and broken down. Cheers very good content enjoyed the viewing 👍

[@AliDymock]

Not sure I understood the penultimate sentence but glad you like it and watched on the big screen (well big screen for youtube anyway!)

[@stephengreen909]

Just came across this channel.. Stunning.. 🌟🌟🌟🌟🌟

[@AliDymock]

Welcome Archie!

[@karenhayhurst2960]

Drywall sealer is to seal the plasterboard when it has been taped & jointed so the paint has a uniformed surface. If you don’t use drywall sealer you could see the joints once painted

[@AliDymock]

Ah so the marketing was correct and it wasn't a waste of money, excellent 👍

[@luv2poker1]

Absolutely brilliant videos mate. Exactly what I needed.🤘🏻

[@POUSEaroundtheHOUSE]

Just been watching some of your garden room videos, I'm a bit late to the party! Brilliant work, really informative and well made videos. Keep up the good work and I look forward to more projects from you in the future....as if you don't have enough to do already!

[@AliDymock]

Thanks dude! I've been watching your vids on and off for years 😀

[@POUSEaroundtheHOUSE]

@@AliDymock I remember you asked me a question about something a year or two ago then put two and two together. I didn't realise you had a channel at the time! Seriously though excellent vids and good luck with your channel.

[@pavelholderik7371]

I was also waiting for next video, I am pro builder but some of your thoughts are very helpful and I must say that I learned from you :) never to olde to learn new bits :) Just putting the windows in over the weekend :) thank for the advice with the FlexTape

[@AliDymock]

Wow I find that quite amazing and humbling.Thanks Pavel!

[@richardcox916]

Great to see another video from you Ali. As spring is just around the corner could you switch to the outside for the next video....Searching you tube, there doesn't appear to be much in the way of information on cladding and materials in the uk !!

[@AliDymock]

It's a good idea, the next one will be on plasterboarding but I could divert after that one. I was going to save to the cladding for the final (ish) video to go out with a bang! If you have any questions though on cladding, shoot me an email and I'll do my best to answer :)

[@dannymurphy1779]

Robin Clevett did a video on cladding the other day. Also Charlie Luxton did one yesterday on the H&R channel.

[@AliDymock]

Couldn't find the first but H+R one was useful and confirmed my thoughts 👍

[@reubend5991]

Amazingly helpful, thank you!

[@smithbuilt]

Sword saw... no kill like over kill. Love it

[@bluestsky1999]

I wonder if a air gap between PIR boards and the outer panels is needed? In case vapour penetrates, it gets some space to dry or drip down.

[@Dave5843-d9m]

Cold bridging is always an issue with heavily insulated walls so foam fill all gaps and ideally tape over with foil tape. Cable conduit is ideal and can be foamed over no problem. Check the regulations but conduit can require a larger cable or for ring mains run each 2.5mm line in its own conduit. Correct spec cable for the load won't overheat.

[@robowen66]

Little tip, saw against an engineer's square to keep the insulation cuts straight. They sail in when the cuts are perpendicular.

[@WestMalvernMummers]

Absolutely great videos, Ali, and they have helped me immensely with my own garden studio renovation. Sorry if this has been asked before but when insulating the floor, should there be a gap between the insulation and the plywood? My floor is over quite a big void as the building is on a steep slope. And there are air bricks all around. So from bottom up it would go: void, then insulation boards fitted between joists, then vapour barrier, then plywood. Then possibly laminate flooring. If a gap is needed, where would the gap be? My feeling is that no gap is needed...? Thanks!

[@fareed7865]

thanks for giving me such a great idea

[@andrewtabberer5610]

Hi Ali, Im interested how you got around the building regs ref 1 mtr from the neighbours garden what was you Class 0 wall option. If this is covered in a video please let me know which video and ill review again thanks

[@4rsxh]

You mentioned at the end of the video you wished you'd left an air gap of a couple of CM between the floor and insulation? did I get that right, so would it be better to sing the insulation board a little lower in the joists to create this gap at the top?

[@amateurvegan2636]

Very informative and well presented, you earned my subscription :)

[@AliDymock]

Why thank you kind vegan 🤗

[@robertdowd464]

Great vid's it seems fortunate that you fully insulated your roof i.e. overhangs , if not then warm air going through the "gaps" in-between the roof beams could condense on the cold vapour barrier ?

[@robertdowd464]

great videos , my garden room is under construction with a warm roof , I haven't put a vapour barrier in so will have to put one in from the inside, you mentioned on the floor not to put polythene sheet on top of ply" why is this ? many thanks

[@nisarzaman]

Just subscribed and just became a fan

[@davidrowe8747]

Another helpful video, thanks! I really appreciate your thoughtful approach to problem-solving and have now watched almost all of your videos. I want to insulate (using foam/polystyrene sheets) a new shed framed out of 2 x 2 battens, which has 16mm shiplap cladding on the walls and 11mm tongue and groove on floor and roof. Can I just check I understand your rationale for where to put the moisture barrier (I'm using polythene sheets)? You suggest the following order from outside to in: (1) shiplap siding, (2) insulation, (3) moisture barrier, (4) sheet lining material (I'm using 11mm OSB). Is your rationale that when inside moisture hits the moisture barrier, you want the moisture barrier to be as far away from the cold source as possible? So, the problem if I switched (2) and (3) above is that the polythene would be close to the outside siding layer, and inside moisture would be more likely to condense?

[@LeeTavMusic]

I’ve only just worked this out today, a year after you asked the question. From looking at a couple of other vids, you would be correct that the vapour barrier would be between the celotex (what I’m using) and the mineral wool (rockwall etc). What I would like to know is if it is recommended to leave a small gap between the inside of the cladding (with the outer being the exterior wall) and the celotex, like I have seen suggested. Just glad I saw your question, I hope you built your shed successfully if so! 👍

[@pmeadows34]

I didn't think the walls needed noggins as other wall framing videos don't include noggins. They make the point that OSB will create the necessary rigidity for the wall studs. But that said, the noggins are certainly handy for sitting the insulation on

[@leemjfreeman9856]

Nice tidy job. Although, in the industry we would recommend against a vapor barrier on the walls, especially for those doing garage conversions (in the comments) as this can make the wall sweat and cause more more problems. A vapor barrier on the floor is a must though.

[@AliDymock]

Yeh for brick or block I'd agree, better to let the wall breathe

[@klaeLIFE]

Hi Lee, my garden room is a concrete block wall with a stud frame inside filled with insulation. I was planning on building the stud wall and having OSB on the wall and wrapping it in house wrap as Ali did and then putting it up against the blocks. Is this not advisable? The problem I have is that the concrete wall on 2 sides is not tall enough (and I cant make it taller) and so the top 50cm of my wall is exposed. Any advice would be appreciated!

[@klaeLIFE]

@@AliDymock Can you please take a look at the comment i left for Lee and let me know what you think?

[@02Tony]

Fantastic to see another video. Thanks to your videos, you are making a huge contribution in helping people such as myself make it possible to build such great buildings.

[@abbbee8918]

Ali, hope you don't mind me asking you (or somebody else who can answer definitively) but I am trying to decide how to insulate the walls of a similar build to yours. Basically I will have from inside out; plaster board, vapour control layer, stud work, OSB board, breathable membrane, batterns, and cedar cladding. How do I insulate in the stud work? Option 1) Full thickness (Like your's Ali) for 'maximum' insulation. Option 2) leave approximately 1" air gap between insulation and plasterboard i.e. insulation up against the OSB. Option 3) leave approximately 1" air gap between insulation and OSB board. i.e. insulation up against the plasterboard. My understanding from speaking to a chap from an insulation seller is that option 2 is correct. Apparently any thermal gains from full thickness filling are equalled by having an air gap and the fact that the foil is more effective at reflecting heat. but this doesn't seem to be the most common. Can someone who can claim to be some sort of authority on the subject explain why all three techniques are in use and which one is best please. Obviously I don't want to fork out for 90mm insulation boards when I can use 70-75mm boards instead. Also can someone tell me how deep into the wall electrics need to be to meet building regs - I've heard 50mm. Thank you

[@AliDymock]

So that all sounds perfect to me and you're on the right video for this so I'm not sure what you're looking for exactly. Either use PIR as I did or thermal wool insulation right?

[@abbbee8918]

Qu1. Air gap or no air gap? Qu2. If air gap, where?

[@Danny-dt8pj]

Great video. Question if I may. Is the plastic vapour barrier necessary if the PIR and taped timber necessary? I read somewhere that it's not necessary as the PIR is the vapour barrier and i was concerned if moisture gets between the two it could cause problems. Cheers great videos

[@AliDymock]

Correct, aluminium tape over the studs is just fine, in fact it's the best vapour barrier as long as it doesn't peel off. It doesn't stick well to wood but does to the foil on the insulation so just make sure there is plenty of overlap (get a wide roll)

[@stevepengilley8166]

Hello, could you please explain why I shouldn't put a vapour barrier on top of chipboard? I just rebuilt my floor with new joists, kingspan insulation (with the foil vapour barrier sides) between them and 22mm t &g chipboard on top. I have made air vents through the raised foundation walls and fitted a moisture barrier on the dirt ground and walls etc all sealed to stop damp coming into the void under the floor. I was then going to put a radon barrier (I'm in Denmark) with built in vapour barrier and footstep attenuation on top of the chipboard flooring, then a wooden or vinyl flooring on that. As far as I can tell that's where it should go: between the finished floor and the subfloor. Isn't stopping the vapour in the warm air of the room reaching the chipboard a good thing?

[@ruuubarbski]

Nice garden kill room.

[@AliDymock]

😂exactly what my mate said. It looked like a scene from Dexter!

[@warrilow2008]

Hi Ali - following closely as im about to take delivery of my log cabin. when installing the PIR board in the walls, i noticed that you didn't leave any gaps or spacers behind them for air flow. i trust your judgement as all of your decisions are research based, so would be good to understand why you didn't do this. your words will give me a guide to if i build a small air pocket behind the PIR or just slot it in.

[@AliDymock]

The idea is that the battens that go on the outside between the wall and cladding create that air gap instead of doing it between the studs.

[@negara54]

I spoke to a technical adviser at Celotex who told me that there should be some ventilation behind the back of the insulation and the OSB, so to use 80mm thickness insulation set against some noggins to prevent it touching the outer surface.

[@shug176]

I have 50mm pir board but my shed is 70mm slots can I use a 25mm packer then tongue & groove straight over the kingspan?

[@SailPink]

Excellent however did you consider Kingspan SIPS for floor, walls and roof . A barrier should be a breathable membrane for timber frame to avoid interstitial condensation ?

[@AliDymock]

I did look at SIPS and do think they are very good but for a few reasons I decided to go with timber framing - I think it's stronger, you can change your design at any point, more bespoke etc. You're right, the breathable membrane is important but goes on the outside of the the building - see Part 12. The vapour barrier (impermeable) stops or greatly slows vapour getting in the walls and the breathable membrane (permeable) allows vapour out to the outside.

[@tonyshaw7272]

Must admit... daunted by a build... torn between the adventure of getting exactly what i want and the safe option of buying an off the shelf cabin.... so much conflicting advise on social media... vapour barriers, membranes and where to have airflow for damp and condensation prevention are my latest struggles.... im getting a little lost

[@AliDymock]

Well I’m not going to say that self building is quick or easy but it is very rewarding and you’ll learn new skills doing it. It IS very achievable. As for membranes, understand the science first and then it becomes clear.

[@tonyshaw7272]

Ali Dymock thanks Ali... if you get a chance what’s your opinion on this so far.... kzbin.info/www/bejne/eoOvdZaDgryGeNE

[@vassy5447]

Hi. Great video. Watched most of the videos in this series. Well done. One question for you please. How do you hang something heavy on an insulated plasterboard please? Thanks

[@handle1196]

Have you ever used EPS insulation sheet. Been looking at it today, it says you need to go 30% thicker than pir but its 50% cheaper and doesn't off gas so therefore retains its r value forever where as pir drops off a lot over time.

[@AliDymock]

I'm aware that there can be a drop off in PIR that has gas in it rather than air as that gas escapes over time - a bit like a double glazed window. If you have thicker studs, say 6x2"s then EPS or XPS might be a good option but no I've not used it. However I'm thinking of building another garden room with a concrete base and it's no big deal to dig deeper to get that extra thickness of polystyrene and save the money over PIR so defo worth considering. Overall it depends on how warm and fast you want your GR to heat up. Many houses have no insulation and they're perfectly liveable so polystyrene is certainly better than nothing. Go for it I say.

[@handle1196]

@@AliDymock since posting this i had a look into the eps and was surprised that it is highly flammable. I thought it might have been treated for this type of use but seems not. I suppose it depends what your using it for and a garden room isn't a livable dwelling but they are a big investment. I've not looked into xps to compare or super foil/super quilt.

[@Dontmindme__]

FYI no minimum height for consumer units from floor on things like garden rooms as usually they don’t come under building regulations. Great vid btw 👌🏼

[@silentvibe]

Great videos thank you. Any chance of a rough cost estimate on all the materials? Thx

[@AliDymock]

Glad you like them! Umm I haven’t quite totted it all up yet but will get to that. I think you can build something similar for around 12-25k. There’s a big range because of choice of materials. Obviously a 3x5m garden room would be less than half the cost of this.

[@silentvibe]

@@AliDymock sorry just noticed your reply. Thx..that really helps. all the best. 👍

[@deepwinter77]

Do you need both a polythene vapour barrier and a tyvek barrier. I've read some contradictory information, but from what I can gather Tyvek alone would be fine. Would love some input from anyone that has some xp in this type of build. I'm building a workshop.

[@kerrmckendrick4517]

Brilliant bit of video/editing work. It must have been as much, if not more, effort than the actual build itself! Anyway it's totally inspired me to get going and I'm now at the PIR flooring stage. Re newer advice about putting a vapor barrier between the ply and PIR/joists (with air gap). As with an earlier video, presumably there would be no need to glue the ply to the joists anymore to prevent movement? would you recommend another solution to cater for movement?

[@AliDymock]

You're so right, it was and is much more work than the actual building work! Yeh good question, you don't strictly need the grab adhesive, just helps prevents squeaks and keeps the floor solid. Even if you put down a polythene sheet you can still use grab adhesive as the screws will hold the ply/OSB in place 👍

[@Bart-dg6qv]

13:36 I'm wondering if there's going to be moisture between that green poly and styro filled wall?

[@AliDymock]

There shouldn't be, nope!