Vapour membrane > T.Frame walls.

[zoothorn]

Hi- I'm a bit stuck on the next step on my TF 2-floor extention. Done the kingspan (2x 70mm).

 

Do I have to put a vcl membrane on next or something, before the p'Board?

 

My builder I think mentioned it back in oct (he's built main part of extention > me to do all inside stuff).

 

Thanks- zoot

 

 

 

 

[nod]

Looks tidy Zoot

 

You can rap a membrane from the ceiling to walls 

Plenty don’t 

Your good to go with the plaster-boarding if all your services are in 

[zoothorn]

4 hours ago, nod said:

Looks tidy Zoot

 

You can rap a membrane from the ceiling to walls 

Plenty don’t 

Your good to go with the plaster-boarding if all your services are in 

 

Hi Nod, but what I need to know, is if its compulsory to add this vpl membrane thing (I've never seen, or have any idea or any info on it.. both Youtube & the www isn't providing any clarity as I'd have thought, on even one good eg) for an extention now to pass B.regs. A definite answer.

 

Your post -suggests- its not compulsory. But there's no point me doing all the stages of interior work with the intention to pass B.Regs, for the officer to ask "is there a vcl/ no/ go back & put one in or doesn't pass then" if I've decided not to if I've established that its perhaps not compulsory.. but in fact it was.

[nod]

No it’s not compulsory 

 

[zoothorn]

45 minutes ago, nod said:

No it’s not compulsory 

 

 

Hi Nod. Ok thanks.. is there somewhere you've read to know this as fact? Or maybe you have BCO experience-?

 

Tbh if its a vapour layer to prevent moisture (from me emmitting it presumably), getting to the PIR/ timber frame.. erm.. how would it get through a plastered plasterboard anyway-??

[Mr Punter]

VCL is polythene which vapour does not travel through.  Plasterboard is vapour permeable.  Odd that the studs either side of the original window opening do not go down to the sole plate and that there are two top plates.  Did the design change after manufacture / design deadline?

[nod]

You could check with BC if you are worried 

Or use a foil backed or foam back plasterboard 

 

 

 

[ADLIan]

The use of a vcl is shown in relevant Bldg Reg Approved Doc & British Standard (and I believe timber frame guidance from TRADA)

[andyscotland]

As I understand it a VCL is required - it can be done by taping the foil faces of the PIR across all the timber but that's a bunch of hassle and not as effective as a standalone layer.

 

It's variously described as Vapour Control Membrane / Vapour Barrier / Vapour Check (with some arcane technical differences).

 

You don't need any of the fancy expensive ones though for your purposes. A roll of DPM or similar heavy duty polythene is fine (semi-transparent is easier for seeing the studs etc for fixing boards but I think a bit more expensive).

 

Given how susceptible timber can be to damage from moisture accumulating through condensation on the cold side of the insulation, and that you can get a roll of plastic fairly cheap and have it up in no time, I'd say it's a no-brainer.

[zoothorn]

44 minutes ago, ADLIan said:

The use of a vcl is shown in relevant Bldg Reg Approved Doc & British Standard (and I believe timber frame guidance from TRADA)

 

Hi ADLlan,

 

I'm sorry but can you translate this? (is relevant, or in relevant.. is there a typo here: if so "is relevant" means the sentence makes sense, & suggests [but only a suggestion- nothing definitive] that the vcl is needed). As it is "the use of a vcl is shown in relevant.." doesn't make a logical sentence: I wouldn't be surprised if this is worded exactly like so, wherever this is from.

 

Christ why can't this building stuff be comprehensible!?! its absolute insanity.

[zoothorn]

29 minutes ago, andyscotland said:

 

Given how susceptible timber can be to damage from moisture accumulating through condensation on the cold side of the insulation, and that you can get a roll of plastic fairly cheap and have it up in no time, I'd say it's a no-brainer.

 

Hi andyscotland. Understand majority of the post thanks. Ok so if as Peter suggests I can can get some stuff from screwfix, then of course it makes sense to consider doing this additional job. But how its done I have no idea.

 

Your last paragraph above: when you say cold side of the insulation, do you mean the backside (foil-back) of the PIR? or the thick shiny vcl outside of the timber frame, in the cavity? or do you mean the face-side of the PIR? (showing in my photo #1)?

[Onoff]

When I did my ceiling I foil taped all the joints.

 

 

 

When I put the boards up I laid the vcl on top then just lifted up with the board lifter:

 

 

[andyscotland]

48 minutes ago, zoothorn said:

 

Hi andyscotland. Understand majority of the post thanks. Ok so if as Peter suggests I can can get some stuff from screwfix, then of course it makes sense to consider doing this additional job. But how its done I have no idea.

 

Get a big roll of plastic. Double sided tape it to cover the whole walls with as few joints and penetrations as possible. Anywhere it has to join, overlap by 15cm and use wide foil tape (also screwfix/Toolstation) along the joints. Overlap it with a horizontal plastic sheet covering the bottom of the ceiling joists. Take it into the window bays etc as well and seal it up to the frame with tape/silicon. Ideally join it to the VCL/DPM at the floor, or seal it round the bottom edges.

 

You're aiming essentially to make a complete plastic bag inside the room.

 

The double sided tape can be a generic one from Screwfix etc, just needs to hold the plastic in place while you put the plasterboard up: ultimately the plasterboard will hold it in position and clamp it onto the tape/silicon round the edges to keep the seal tight over time.

 

You can also use some staples to hold it initially in places it wants to pull off the tape, then just put a square of foil tape over the staple.

 

48 minutes ago, zoothorn said:

Your last paragraph above: when you say cold side of the insulation, do you mean the backside (foil-back) of the PIR? or the thick shiny vcl outside of the timber frame, in the cavity? or do you mean the face-side of the PIR? (showing in my photo #1)?

 

The cold side is the side nearest the outside. Water vapour will travel there from the room (e.g. through little gaps between cut bits of timber, through gaps that form as the timber shrinks, through tiny natural cracks that will open up in the grain of the timber itself, etc). Then it could condense into liquid water and start to cause problems. Same basic thing as when you wake up in a tent on a cold day and the inside surfaces are soaked with the water you breathed out in the night.

 

The "thick shiny vcl outside of the timber frame" should be (and likely is) a breather membrane rather than a VCL. In theory that will allow vapour out of the wall and into the cavity before it condenses. In practice there can be a mismatch between the rate vapour gets in from the room and the rate it gets out through the breather/cavity : the more you can keep the moisture out on the room side the better. The external breather and internal VCL work as a "belt and braces" pair to make sure the wall stays dry.

[zoothorn]

@andyscotland & @Onoff

 

really appreciate the info, & pics there. That robot lifter.. jeepers wish I had one! its not too high tho my 1 ceiling to board @ 2m.

 

Ok, in my upstairs room (bedroom) the ceiling plasterboard & fluff above my builder has done.. thought best as at 2.3m H, I know I'd struggle pB'ing this high onto roof truss whatnots. So this hasn't been placcy sheeted. So is it still advisable to sheet the 3 walls?

 

I think perhaps, as I know I'd struggle doing placcy sheeting on lower room ceiling, I might just do the same: just sheet these 3 walls too.

 

I'm also wondering if its worth sheeting the lower workshop room at all, as its not a bedroom (no excess of human oomschka emitted), just a workshop.

 

What do you think?

 

 

[andyscotland]

I'd still do the upstairs walls, use mastic/silicon to seal the plastic as thoroughly as possible at the wall/ceiling junction.

 

And I'd still do downstairs - even tho it's a workshop you will still be breathing in there (and possibly moisture coming off any new wood that gets delivered?) etc and the air temp will be higher than outside so there's still a condensation risk.

 

You can probably get away without doing the downstairs ceiling, vapour between the floors isn't a major problem (as both sides of the ceiling/floor are at similar temperatures), the main reason to do the downstairs ceiling is to stop moisture getting there and then travelling along to the outside walls. If you did the wall and sealed it around the top, ideally going up between the joists over your offcuts of PIR, that won't be perfect but probably OK. That said I think you're insulating from below? In which case I'd reckon stapling a plastic sheet over as you go would keep the insulation in place rather than it drooping and getting in your way when you come to plasterboard...

 

Slightly off-topic, but you'll find it hard work boarding the ceiling without a board lifter, especially on your own and especially with full-size boards. It's not so much the height, but the business of holding the board above your head, without it snapping or moving into the wrong position, while you get the first screws in. The first few screws won't hold the weight on their own (they'll just tear through the board if you stop supporting it) so you're holding the board for a while. Also it will droop, so when you pull it flat it will be slightly "longer" than it seemed and may end up too tight to the board before.

 

It's not impossible - I replaced our kitchen ceiling like that, there wasn't space for a lifter between the cabinets etc. It was very hard going, and there were some larger-than-there-should-be gaps between boards that I had to fill afterwards. But there was only once I found myself stood astride the sink, balancing a plasterboard on my head and calling for my wife to help...

 

You can make timber props to help. You need one that's just a length of scrap a bit longer than the floor-to-ceiling height, with a ~600mm T-piece screwed to one end. And one that's more like a bird-table with a cross-shaped base (may need some weights on it), vertical section slightly shorter than the room height, and a T-piece on top. Stand the bird-table by the wall, rest the end of the first sheet of plasterboard on it. Lift the other end up and use the T-brace at an angle to wedge it against the joists. Screw the board into position, working from the wedged end to the bird-table so that you're working all the slack/droop to the free end. Then move the T-brace so it's still wedged on the first sheet, but overhangs the join, with the top of the T angled downwards away from the first board. That will give you a ledge slightly thicker than the PB to rest the end of the next board. Lift the board into position, then slide the bird-table under the free end (helps to have already got it in roughly the right place - could also make it easier to move with some casters on the base if you have some lying around). Then screw the board up, again starting from the wedged end.

 

It's just about viable to work like this single-handed, but you will find it hard to get the boards neatly aligned and are bound to drop the prop / get the board in the wrong place at least a few times. You may need to screw a scrap of timber to the floor at the bottom of the T-brace to stop it sliding out of position.

 

A board lifter isn't that expensive to hire (or from a quick google you can buy pretty cheap ones which you might be able to re-sell) and will be a lot quicker, especially because once the board is up there you can move it around to get it exactly where you want it.

 

 

[zoothorn]

Hi @andyscotland big thanks for that info too. Ok my plan is to placcy all the walls ( total, 2 rooms) but perhaps too much for me to plastic the ceiling of lower room, but I will consider it if I can get some direct eg Youtube clips I can follow. I do have a very useful extra pair of hands, my nice electrician who I can pay his std rate/ hr for any other jobs: the pB job I've got him lined up to do the job with me.

 

The upstairs bedroom ceiling is already plasterboarded by builder (not too great tbh) so it'll never be super-sealed with placcy anyway.

 

Re. plasterBoarding the ceiling: two things on my side, are height is only 2M.. & as said it'll be two of us doing the job: does this mean its feasable to do without a board lifter then?

[Declan52]

This will give you an idea. 

[Onoff]

3 minutes ago, zoothorn said:

Hi @andyscotland big thanks for that info too. Ok my plan is to placcy all the walls ( total, 2 rooms) but perhaps too much for me to plastic the ceiling of lower room, but I will consider it if I can get some direct eg Youtube clips I can follow. I do have a very useful extra pair of hands, my nice electrician who I can pay his std rate/ hr for any other jobs: the pB job I've got him lined up to do the job with me.

 

The upstairs bedroom ceiling is already plasterboarded by builder (not too great tbh) so it'll never be super-sealed with placcy anyway.

 

Re. plasterBoarding the ceiling: two things on my side, are height is only 2M.. & as said it'll be two of us doing the job: does this mean its feasable to do without a board lifter then?

 

Perfectly feasible. Making up a wooden T bar (or two) can help.

 

Just YouTube "plasterboarding a ceiling". Lots of videos.

[zoothorn]

2 minutes ago, Onoff said:

 

Perfectly feasible. Making up a wooden T bar (or two) can help.

 

Just YouTube "plasterboarding a ceiling". Lots of videos.

 

Hi Onoff.. great then that's the plan. Will look up making a t thing.

 

Re. the placcy stuff.. I seem to recall builder saying 'visqueen' or summat? now, is that the pro stuff he'd use & you suggest a cheaper alternative- is that the idea?

[Onoff]

3 minutes ago, zoothorn said:

 

Hi Onoff.. great then that's the plan. Will look up making a t thing.

 

Re. the placcy stuff.. I seem to recall builder saying 'visqueen' or summat? now, is that the pro stuff he'd use & you suggest a cheaper alternative- is that the idea?

 

Yes. I used the cheap stuff as per the Screwfix link I gave.

 

Cuts down the draughts via any slight gaps between pir and studs you may have missed. A cheapo staple gun is handy too. I have two from Lidl.

[zoothorn]

Aha ok- I usually miss s'thing & pick up when I go over the replies a 2nd time as I tend to do.. cheers for that.

 

Its a shame I can't make the upper bedroom ceiling airtight (already pB'd,  & gaps a plenty): its here especially I need it, as its leaking like a sieve with loft/ new roof above & wind hitting it so hard. Is there anything I can do, or is it just a Q of hoping the plastering job yet to do is good enough to form somesort of sealed 'lid'?

 

 

[Onoff]

This sort of thing. Still from a YouTube vid. Bloke's doing it on this own. He's standing on a hop up of some sort. T bars are made to such a height so they "wedge" near vertical. Best to have two people. It's a bitch when on your own and a T bar slips and falls and the board comes crashing down. Loads of ways to do it. Watch YouTube vids!

 

[Roundtuit]

51 minutes ago, zoothorn said:

 

Its a shame I can't make the upper bedroom ceiling airtight (already pB'd,  & gaps a plenty): its here especially I need it, as its leaking like a sieve with loft/ new roof above & wind hitting it so hard. Is there anything I can do, or is it just a Q of hoping the plastering job yet to do is good enough to form somesort of sealed 'lid'?

 

If you haven't got a VCL in your bedroom ceiling, I'd take the plasterboard off and do it again to be honest. Plaster might give you an airtight layer, but it won't stop moisture migrating.  If the pb is screwed on, most of if will be reusable.

[zoothorn]

7 minutes ago, Roundtuit said:

 

If you haven't got a VCL in your bedroom ceiling, I'd take the plasterboard off and do it again to be honest. Plaster might give you an airtight layer, but it won't stop moisture migrating.  If the pb is screwed on, most of if will be reusable.

 

Tbh Roundtuit, I couldn't contemplate/ face this prospect of undoing, & especially putting up a sheet it'll be a n'mare job never having done before. I paid the builder to pB & loft-fluff the upper room, & its done now (he only mentioned 'visqueen' with regard to the walls too).. besides its as per the rest of my rooms, & there's no problems here without a vcl.

 

I know its not the perfect job, & falls short of the top bullet-proof quality you guys do.. but it'll have to suffice for me. Matey above on his hop-up & t-things isn't going placcy sheet.. & he's far more pro than muggins here.

 

Thanks, zoot.

[PeterW]

Decent plastering job will make it pretty airtight so don’t panic. I would use a cheap polythene layer for airtightness on the ceiling under the insulation in the workshop, bring it down the walls and tape it. Then board it when you’ve carefully measured and marked where your down lights will go.