Insulating a Timber Joist Suspended Floor
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- เผยแพร่เมื่อ 26 พ.ย. 2024
- Well over 5 years later and I am back at it! This is how the renovation all started so at least we had a tried and tested method to use. We had intended to use solid PIR insulation however for several reasons chose to switch to mineral wool and save the boards for the next part of the build, all of which will be covered in the next video.
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Thanks again Tim I have learned so much from you. I’m the summer I will be insulating beneath my floor boards and will be following in your steps.
If anyone is doing this, there is a much simpler way of installing the membrane without hugely increasing the waste. Take some left over ply or OSB or if you don't have any just take an usb board (it's cheaper) you need to cut 1" strips (could be also wider if you need to increase depth etc. You run the membrane around the strip ( the direction depends on if you are extending the joist depth or just fixing) and then nail/screw/staple the strip/batten to the bottom of the existing joist. You'll end up with an inch (or more if you are extending) of waste per joist but you don't need to go on the floor, you work from the top and you save a lot of time and your back. But the video is amusing to watch! Also, if you have some roof battens just use that. This obviously doesn't work with rigid foam buy you should really think twice before installing PIR under your floor. It is not fire retardant in the slightest and you may need to meet code requirements which means extra fire measures. Not to mention that I'd love to see you run heating pipes in PIR!
Great tip I was told for stapling vapour barrier is to use bits of cardboard and double staple through. Spreads the load of the staple point and assists with them not pulling through. Great videos really enjoying 👍
Ended up doing just this but hitting staples through 3mm ply offcuts, worked great.
Tim i whole wholeheartedly love your channel. The effort you go though to bring us your projects is fantastic.
Well done, Tim. Another great video. You’re the most patient bloke I know!
The easiest way to get started is to wrap a small batten then fix the batten to the underside of the joist. Same with the last one on the run, that way to can fix it to the inside of the joist. Also makes sure everything is level (-er, ish 😉)
Good effort again working and moving stuff. my garage conversion is in a very similar clutter and hard to stay motivated :-) but the end is near looking forward to the next instalment
Fair play bud this is a great and very useful video. You have done amazingly well just getting on and doing it and filtering out the keyboard warriors. Lots of opinions out there. It all works though. The main thing is you did it!!! 10/10
If I can give you a small advice try cutting the isolation in package with knife long enough you can cut meters in matter of seconds
Or you can cut the roll with an old wood saw
Bread knife works a treat
Tim, is it not easier to cut the rolled insulation to width whilst it's still in the wrapper and then just cut to length?
What I've done in the past is to remove the build up excessive dust rubbish and soil which builds up over th decades especially with Victoria properties, then I cover the entire dirt with DPM and cover with concrete not too much enough to keep the DPM flat. Obviously where there are footings supporting sleepers cut around. This reduced the rising damp by at least 90%. If its a Victorian house the floor joists and sleepers which are fine need to be treated with preservative and dry damp treatment, face mask and use and gloves for PP are required and make sure the room is well ventilated and spray on( use the green Ronsil fence sprayer...they cost pennies on ebay). Broken or rotten timbers need to be replaced by tanalised timbers only.
Next plastering scrim and screw to lower side of joist and then take the scrim to the next joist running parallel to it and to the same thing you and do this to the width of the room and then repeat again 400mm apart and continue until you have done the length of the room you have now created a lattic for the 100mm rockwall to sit on. If budget allows put 70mm Selotex or Kingspan in between the joists first and then the 100mm Rockwall. Refit the floor boards...job done. Scrim is a lot tougher than breathable roof felt and easier to install.
Hi, we have 3 inch joists... do you have any idea of how to add insulation underneath these joists as well as in between? To reach 200mm of insulation?
Got one of them DIY saviours myself, can’t do without them and they don’t want wages👍❤️
I use garden fabric stapled to the bottom of the joist. The material is woven so breathes. Allows water to fall through should there be a spill. It is cheap, strong and easy to fit. I fold the edge over to double up in places for strength I use a compressed air stapler. It won't stretch and has worked well with mineral wool. I also dug out the solum and concreted in a DPM and enlarged air bricks. I don't DPM the warm side. Good ventilation does not require it. At floor level there should be minimum moisture and what penetrates will evaporate is a well ventilated void, physics make sure of that. Have had it in two houses now and all bone dry - IF the solum is dry. Victorian houses are a challenge but it's been up 120 years and it was the 60's and 70's vandalism that caused the issues. Oh I forgot to say I put 600mm of solid 4 inch /100mm insulation above dwarf walls to give 2inch/50mm of space for air to move. This insulation fitted with batons on joists nailed in place.
Good watching your approach and that you will try different materials and methods. Keep going your getting there and good luck with the expanding family.
Interesting insight, did you look at limecrete floors instead of concrete? Have a Victorian house with deep void and bitumen damp proof course has failed in places with wet caly soil below.
Jim Johnston I dug out old rubble and building materials left post construction (1890), dug out the sand and stone from dressing sandstone in construction phase and soils to above foundation depth. I then put down 3 to 4 inches of river bed (rounded) gravel, placed a DPM thickest I could find on top then a poured regular concrete. The concrete only serves to hold the DPM in place and stabilise the base. Concrete designed and placed to stay a solid slab without cracking. It's purely physical and will not absorb / hold moisture ( waterproofed additive to minimise) so even if I get flooding it's a pump out and dry out operation as worst case. I now only have moisture penetration through perimeter external walls which is natural and subject to equilibrium with. Outside soil moisture which can be controlled by reducing outside soils to original height - it has increased 5 to 8 inches in 100 years with 2 "new" surfaces being added including tar macadam type surface. I also intend putting a gully drain around perimeter of house and a novel subfloor ventilation to increase evaporation rate. It's all a balance of moisture in being lower than moisture out capacity. First room had a RH of 75% on completion in June and is now sitting at 55% in winter with the active ventilation still to be activated. I am aiming for an RH of 50% +/- 5% all year round in the room with NO vapour barrier in the suspended floor. I seal all the floors with either ply or sealant where there are cracks or gaps. Anyone that has been in the winter mountains know that even snow has evaporation in sub zero temps - as a physicist I know this so modest moisture movement is not a problem AS long as the subfloor is ventilated properly - I may post a couple of videos to show my methods if I get round to editing. I'm not as savvy as the restoration couple. Lime based concrete is NOT what you wand for a vapour barrier as it is porous. I have reprinted sandstone walls with lime mortar after removing cement mortar I do want a porous material here to unload moisture from the sandstone walls as it is meant to. I have 2 foot thick solid sandstone external walls. I am getting there and the comfort level of the house is noticeably better in completed rooms.
Thanks David, any videos you have would be very insightful as it sounds similar to what we face with an 1890s house and various modern bodge jobs by builders in the 1980s. Please let me know if you post anything!@@davidramsay6142
Great video and absolutely the right thing with the vapour barrier, bit of a faf fixing to the underside though 👍
The reason not to use netting is that it’s open to the air and you’ll loose some of the value of the insulation as the air pulls heat out of it. Part of the problem with underfloor is that you have 2 sources of moisture, one the floor and 2 the room. Typically the floor would be a bigger concern since it’s going to get some water ingress when it rains and that will evaporate somewhere. However with adequate airflow any surface condensation will evaporate and be carried off in the air.
Great video and channel - I’ve found it very helpful. Would you be able to provide a link to the insulation you use please?
Do you have a list of the products used. Especially the Breather Membrane. Thanks. Great channel
Great video.. thanks. What the product you used for the breathable membrane?
Are you sure nailing to the underside is allowing tImbers to breathe sufficiently. The idea of flowing the membrane over the top of joists allows timbers to benefit from the airflow beneath?
Could this be done under a log cabin cos kingspan is disgustingly expensive
Fair play for not falling through the joists shifting those appliances
I could remove the floor boards in the bedrooms and insulate the joists but it's a new extension which was done about 10years ago there must be a reason to why they did not insulate the flooring? The block work on the exterior has small vent covers that blow wind through the joists than then blow done into the kitchen down lighters. So annoying. I'd like to know where you get your drive and energy from doing all the stuff you do?
Great video as always I love the way you just get on with it.
Hi Tim, If you're stapling a membrane layer to the underside of the joist, can you think of any downside to using insulation deeper than the joists (not compressing the insulation)?
What is the brand name of the breathable membrane that you used in the video ?
Hi. Hopefully you can help, I'm just renovating our lounge suspended floor and been using your video's as a source of inspiration. I have just laid the DPM but am having great difficulting taping it tothe walls. I have tried every type of tape but none seem to stick very well. So I was wondering if you could let me know what you used please?
If its a ventilated floor the membrane will better maintain dead air than netting and be warmer .. right?
fantastic video tim iam glad you stopped as is getting late hard to concentrate enjoyed the video.
Its funny watching you go through the same decisions I did. Started out with tarp overlapping the beams then moved to underfelt at the back of the beams.
Only guy I would trust to work on my house, contractors don't give a dam about your property.i have even Heared them in the pub laughing at how the done a crap under the floor boards.
thats sick
I recently added wool insulation under my floor via the crawl space. Biggest issue was I have concrete joists so was unable to easily affix the netting. Ended up using command hooks with a sticky backing. As not enough room to swing a hammer. Any suggestions of a more robust way of fixing the netting, not that I’m in a rush to spend another weekend under there!!
Then what is better option support netting or breathable membrane?
So just to be clear, the side that would face the sky on a roof, is the side that faces down towards the earth?
I'm insulating my nans old house from the crawl space, the floor boards are quite scrappy so I was going to lay 10mm ply cut to look like boards across, would vapour sealing ontop of the original floor be ok ?
Thanks for the vid very helpful. Word anyone say you need a vapour barrier if your doing this to an upstairs room, over a dry garage actually. Which is freezing cold!
While it could be ok if garage vented and all breathable. The risk of condensation much greater as it will get colder as air moves down.
What happens to the vapour barrier when you might want to add underfloor heating?
Is there a video for the insulation using the netting ?
Great vid as always. I was thinking im sure i missed your dads resin floor video.
With this membrane are you trying to keep moisture from going down through it or up from below into the house?
Let's say you spill a cup of coffie or have a leak somewhere. Will the liquid just not sit under whatever floor finishing you have and be trapped? Not a criticism just a question. Thanks
@@theutilityarborist2428 i was thinking the same
Hi Tim, planning to do a garage conversion, your videos have been great, just a question i need to build a suspended floor to bring it level to the house but would you do the floor first and then build the stud wall which will sit on the joists?
Loving these videos! Is there a handy website people go to for the building specs for the UK? Distance needed between joists, the dimensions of the wood needed for different supports, stuff like that? Thx tons!
Just search for floor joist span tables. 👍
@@TheRestorationCouple Golden! Thanks heaps!
Hi. Great channel; really inspirational.Loved your original underfloor insulation series and used your guidance to complete one of our downstairs rooms; its been great. I'm now looking to do our hallway but rather than re-use the floorboards, we want to lay down t&g cement board instead as the final finish is going to be parquet wooden tiles on top, so replacing the floorboards will limit the overall floor thickness.The only issue is that the cement boards have to be glued to the joists (as well as nailed) and this raises an issue regarding the damp proof membrane. I'm toying with going without a membrane as the cement boards are supposed to be waterproof.Do you have any thoughts?
What brand / product did you use for the membrane? Tia
So so funny when you run out of staples
Funny to watch perhaps! :-) It's those moments when you wish you had an apprentice of some sort... one that happens to be stood there at 10pm with a pack of staples!
Are joist every 16inch apart
how long did the job take, thanks
Vapor Barrier should always be on the warm side of the floor, walls and ceiling. Is that a True Vapor Barrier you are using ?? or is it some sort of breathable membrane such as house wrap that goes under siding? Using Vapor Barrier on the cold side will trap condensation inside your floor which will get your insulation Batts wet, grow mold and eventually rot the wood.
Yes vapour barrier went on top. The breather membrane underneath is just to support batts, we have used mesh or netting in the past.
Posted 1 minute ago, instant click.
Will that first layer prevent mice from nesting underneath?
Good job!!
Why vapour barrier? What moisture you have under the floor... should stay there! If unwant to hold insulation up... just use strips of 4inch dpc
Is there a follow on video to this where we see the project progressed & finished?
Many, coming out each week. 👍
Your channel is pretty fun guy!
what type of stapler please?
AMAZING!
Not sure if I missed it but do you have an external access point for the crawl space etc‽
Yes, hatch from the other room. Just has some tools in the way at the moment!
Hi Tim. My joists above my kitchen and bedrooms have no insulation what's so ever and you can feel a draught coming through the kitchen down lighters. Any advise? Is there a reason for joists sweating with insulation?
Most likely condensation forming from warm air escaping up through lighting. More modern light fittings may be better.... Can you not insulate?
Membrane top and bottom to prevent thermal wash out
Wouldn't use rock wool, it deteriorates and compacts with age. Use hard stuff like Celotex.
Hi Tim, could you please offer me your thoughts. I have a bungalow, recently moved in to with waist height under floor crawl space. And desperate want to insulate asap. We have Laminate floors throughout, so too much trouble lifting the floors to insulate. I have plenty of crawl space to move around underneath, but need to understand the best way to move forward. I like what you have done in this video. But my problem and worries are is it a must with both layers of membrane ?. Could you spare 2 mins and offer your thoughts please ?
The membrane below it’s really just to support the insulation but is a good way to do so. The vapour barrier on the warm side, above joists, is important to prevent condensation. However it is possible that your laminate underlay will already provide that so it may be possible to do everything from below without too much risk.
The Restoration Couple Thanks Tim, just read all the comments. I think I’ll try the batts instead of loft rolls. With either bend sticks holding them in place after top layer. There’s no way am lifting all the top floors so will staple top layer on the bottom of the joists then fit the batts
@@game4alaughman was wondering how you get on because I'm in the exact same situation as you. Looking to insulate under our house with plenty of crawl space but won't be able to lift all the flooring up.
@@MrAas41 covid came pal and I had to retire, managed to get a free home insulation done by Scottish gov, opted for a spray foam.. wow what a difference, it really made the bungalow much warmer. The company was meant to use a wee robot that sprayed the foam but they couldn’t get it working properly so was done by hand with the hose. Yeah I would deffo recommend it, if you want to look down that rd 👍 no problems so far at all.
Only thing I wish I had the cash for before was to get sockets rewired 1st but it’s no bigger atm
@@MrAas41 it’s amazing the amount of heat I was losing without any insulation
Seriously, I’d be having full blown panic attack under them joists!!! Claustrophobia City!!
You have a lot of space under the floor, you should insulate timber joist underneath and you should make vertical insulation of your foundations. What you did is not enough and you will get cold joist and cold wall right above the floor. This usually cause rotten wet walls 150-200mm above the floor, rotten furniture and obviously make your house cold. If very cold outside and warm inside you chipboard will form condensation where in contact with the floor joist. Squeaking will also start with screws. Floor should be glued with polyurethane glue to the joist. Claustrophobic low ceiling.
Great video. Im planning an extension over the garage. I was thinking of battens and plasterboard on the block walls rather than dot n dab. That way i can insulate between as well as the cavity. If the insulation is foil backed is that my vapour barrier sorted? Also what would you do for the floor. Its a cold garage below
Yes the foil back pb is vapour barrier. Regs with garages is quite strict, I think you have to use thicker boards and fire resistant materials. Best check with BC.
Excellent video, Why do some people use king-span for this job, Is it cheaper this way or just less work. Thanks.
I have used both and actually have just shot a video on why I went this route, will be out in a day or two. In summary though, by filling the joist depth with soft insulation equals the same u value you would by battening each joist and putting in PIR/kingspan. Stud walls and roofs are usually not thick enough to fit enough mineral wool to meet minimum regs hence why I used PIR everywhere else. .. and yes cheaper and nicer to work with too.
@@TheRestorationCouple I am going to do this job in my lounge so very interested in this. Thank you for your reply.
I cheaped out by going with loft type rolls, I would suggest though that it's worth getting the more dense rolls or slab type as its a better fit and likely slightly higher performing.
@@TheRestorationCouple Thank you. 👍
warm moist air travels upwards!!!
the memory roll the name of it place to get it from wont to do my floor to lol
👍
Hi Tim can I ask what type of foundations your property has and if you had to do any work to the foundations before you replaced floor joists and reinstated your floor?
The building is the original solid wall structure so full foundations. The floor joists are hung on solid wall and sit on stud wall. Earlier videos will explain.
I don't like running plastic pipes beneath floors, ground floors especially, since "wee timourous beasties" have to gnaw continuously, to file their incisors down, plastic pipe tends to get attacked and causes leaks. Adding insulation provides both an easy source of nesting material and a hop up platform to get closer to the pipes.
Of course, improving insulation and noise reduction is a good thing... but there are drawbacks. Just saying.
I’ll make sure the cat is on guard. 👍
Meow! Purrrrrrrr. I tawt I taw a puddy tat. Good idea to make sure that any external vent bricks are all in tact. They tend to try and come inside around this time of year. If they want to chew anything, better off the electrics---> instant death! But I'm a plumber and as, such totally biased.
I'd have kept it on the roll, roll it under a joist then back on itself, pulled tight then stapled then move to the next
Easier said than done with pipes and cables to deal with
Would you need the vapour barrier on top of joists if you was laying chipboard flooring then laminate, with the laminate underlay containing a dpm ? Would this suffice for stopping the heat meeting the cold air underneath ?
Thanks
Most likely fine. To be honest with both our laminate and underlay no installer we didn’t need it here but for a few extra pennies it’s worth doing especially if it’s somewhere that may be carpeted in the future.
wow!....and you do laundry !?...... wow!
Good video 👍
I never like using wool insulation or any likes of it in cavity external walls. The amount of times iv seen it drench inside walls attracting damp. Its an inferior product as it prevents any ventilation. This is where kingspan comes in..
The vapour barrier issue is a bit confusing 🤷♀️
Simple rule. You just need a vapour barrier along the warm/room side of insulation. Same for roof, walls, floor, etc. Foil faced products have it already so just need taping.
@@TheRestorationCouple hi iam about to insulate under a ground suspended floor without lifting the oak boards. I wont be able to use soft insulation and a net due to not being able to put a vapour barrier between it and under the boards...will it be ok to try and get foil backed insulation between the joists? But I guess I will have cold areas where floor joists are. Thanks for reading.
Tim you are as nuts as i am.
I am in the Bath area, i have just built an annex for mum and dad and am renovating the main house. It would be good to swap stories once this COVID19 has blown over all being well.
Pm me if you want to make contact.
Thought you were pushing it, leave the washing.
Mobile air is the enemy of fibre insulation. A moisture-permable air-barrier is much different from netting. Then again, the wilds of the UK is far removed from my backyard of -40C and car-burying snowdrifts.
I had meant to mention 'air washing', the air flow is ok below the floors but probably not enough to have much effect and with the membrane above at least its not drawing warm air down from the house.
Clearly he's not aware that surrounding electrical cables with insulation is contrary to the regs. Cables covered by insulation should be derated.
1.0 or 1.5 mm lighting cable is no big deal as it's far from max capacity and generates little heat, but strictly speaking, the regs say no. Ring main, cooker cables, shower cables etc should not be covered.
They are all over the country of course and it rarely causes issues but I would be inclined to comply with the regs. They exist for a reason.
If enough slack cable, insulation should go underneath, if not, make an airspace for them or rewire.
Pregnancy cravings?!?! Have I missed something? If so congratulations. Will it 4-1 or 3-2 😉
Yes, they are having another one. Late spring, if I remember correctly. Although I don’t remember which team is gaining another player. ;)
Yep, mid May. It will be a surprise once again but something tells me I'm going to be in a house of girls! The dog and I hold our own... well we try!
First 😉
who was first lol
Allen Hart me
@@petermiller3882 You both seem to of posted at the same time lol...
Allen Hart I’m at the top first post
If it ain’t broke don’t fix it.
First
who was first lol
@@AllenHart999 me
Tim I don't get your DPM method because damp rises! If your concrete floor gets breached then the damp will be trapped in that zone and you will end up with wet rot. Yes you can say there is a DPM under the concrete but who can say if there really is or if it is totally intact and not pierced by a stone or something. Do you have really good airflow underneath? I don't recall you mentioning airvents. It doesn't seem like a good idea to me because what is the DPM doing that the floorboards don't? A DPM there won't impact your energy bill yet could prevent you becoming aware of an issue until it gets chronic. To me this seems to go against your thinking about breathability and two way flows etc. I guess if your airlfow is really good then all will be well but I would regard vents as being the main issue, the more the better I think.
Another slighty related issue - leaking washing machines! Been the victim more than once, my sister also. Perhaps you can get a gizmo to monitor it in some way? The point is even a few cupfuls of water can cause a lot of damage, you can get these very slow drip leaks going on. Just thinking it is a great help at leat having a visual check and not to have the machine rammed against the wall where such things are hard to detect. Anyway HTH's.
Don’t be confused by the fact I used DPM material, it’s just a vapour barrier. With t and g boards and a finished floor it is not that vital but if you imagine our original pine floors with all the gaps it is far more important. In the ground floor of the main house it has a huge impact on heating as cuts all drafts blowing up, or worse drawing warm moist air down. It has nothing to do with moisture below, cross vented air space will manage that. VCL on warm side is usually insisted by BCO anyway. 👍
Well if BC have approved it then it's all good. But what I don't get is you seem to have eliminated all airflow to the bottom of your joists. If water comes in from above won't it just get trapped in the insulation due to the lack of airflow? I am not sure what the point of breather membrane under the joists is as the airflow under there will be removing any moisture.
BC will insist on it so not really an option. Membrane under is only doing the same job as the netting did. It does help with the air wash effect which reduces performance of insulation slightly when using netting. Ventilation under via vents and air bricks is plenty for keeping dry. 👌
Well thanks for the replies, I am not suggesting you are wrong, just questioning if there really is any scientific evidence for using breather membrane under joists??? I take it BC are saying you can use it so as to be able to insulate the full depth of the joist???
It no doubt sounds very boring to many, but I do think with a suspended floor in a utility room the biggest concern is water getting in from above, I can see why insurance companies aren't too keen on the idea. I think if I ever did one I would be tempted to go for the PIR boards, get them very level and use a good sealant tape. Like when I had a leak here on oak boards it was barely noticable apart from a damp smell. Yet when I got them up a shoal of silverfish ran for cover and the chipboard was shot. Just saying if you go with a couple of layers of flooring and PIR boards any leak is more contained, IMHO at least. It is just a thought for anyone else thinking of having a utility with a suspended floor.
Would have been MUCH easier to attach 1"or 2" strips of wood near the bottom of each joist then put/screw thin plywood over the strips then insulate. If damp use all treated lumber.
It pains me to watch you kneel on beams. That would be spy torture to me.
It looks as though he’s wearing knee pads to me (the sort that fit in special pockets on your work trouser legs)
Now you know we go under and over, i would rather use more membrane than crawl about doing a beached whale impersonation 😂 keep up the good work.👍
I'd cringe if you put a foot through the membrane! I always want to see DIY jobs go well👍
I did actually stand on the insulation by accident as I lay membrane down, a couple of hundred staples are surprisingly strong. 😂