Airtight strategy - block built

PROJECT K

Airtightness, oh i should have built timber frame...!:p

I have a fairly clear idea of what to do but thought i would send this out there for any other ideas and to benefit from the experience of those on the other side of a similar self build!

Window reveals:
Plan is to prime blockwork and use proprietary airtightness tape for timber windows to blockwork reveal - expanded metal over and plaster/skim. I have come across a problem where its virtually impossible to fix mesh to the concrete heads and while the tape supplier said you can plaster directly to tape only, they and i would generally recommend mesh also - any other ideas on how to do this? The plasterer suggested some form of skrim tape over the airtightness tape but im not convinced...! I dont want to have to ply this out either as i dont have the depth...I suppose i could try concrete screws (pre-drilled, maybe into plastic sleeves)?

FF walls to ceiling:
Original plan was to sand/cement first the membrane to the walls, then fit ceiling plasterboard and then skim all together (walls and ceiling). Plasterer is suggesting to fit ceiling plasterboard first (35mm services void) then plaster/skim everything - saves having to come back and wet the walls etc. The former i believe is standard <airtightness> practice but i dont see an issue with the latter? Also the airtight materials supplier is suggesting bonding the membrane to the walls first with a glue, is there any merit in doing this if the plaster will overlap by >100mm with mesh over? My immediate concern is that the airtightness test will be carried out after the plasterboard is fitted therefore only access to remediate any issues with the membrane is from the attic...

Junction of plastered walls to stud frame walls:
This is where my first comment comes from - its almost inevitable that in any block house you will come across this type of junction (in my case framing to hide a pocket sliding door, suspended ceiling (edge of slab at landing for example), studding out to allow shower valves (cant recess these in a 100mm block wall!), framing out bulkheads etc etc). In a timber frame house all this would have been much easier and straigtforward. But im obviously stuck with what i have - the plasterer recommends overlapping the masonry component with the plasterboard by approx. 200-300mm to move the stress joints away from the actual junction, then use reinforcing skrim to protect this joint. I will have to then use an airtight membrane behind this and make sure this is also overlapped by the plaster and mesh. Also will have to use concrete screws rather than anchors to prevent air leakage. Any other ideas/experience on how to do this?

Thanks
PK

Strolling Bones

Have you looked here

PROJECT K

yes thanks SB, im well aware of that document - basic and not much help in the real world...!

BarneyMc

PROJECT K wrote: »

Junction of plastered walls to stud frame walls:
This is where my first comment comes from - its almost inevitable that in any block house you will come across this type of junction (in my case framing to hide a pocket sliding door, suspended ceiling (edge of slab at landing for example), studding out to allow shower valves (cant recess these in a 100mm block wall!), framing out bulkheads etc etc). In a timber frame house all this would have been much easier and straigtforward. But im obviously stuck with what i have - the plasterer recommends overlapping the masonry component with the plasterboard by approx. 200-300mm to move the stress joints away from the actual junction, then use reinforcing skrim to protect this joint. I will have to then use an airtight membrane behind this and make sure this is also overlapped by the plaster and mesh. Also will have to use concrete screws rather than anchors to prevent air leakage. Any other ideas/experience on how to do this?
Thanks
PK

Not sure where you're talking about here but I'm guessing it's on the first floor? If so if you run your membrane OVER all internals walls then this will solve your problem? Could be a million miles out here so sorry if it's not addressing your issue.

PROJECT K

No barney, with the exception of one detail the rest are on the ground floor - in this house as is typical i am relying on the plaster as the airtight layer, but there are areas internally that abut external walls that are framed out etc so the strategy has to change to an airtight membrane with plasterboard. These issues are quite common, i am guessing most are just ignored and wont significantly impact on overall performance but thats the problem when you get too involved in the process!!! I have my ceiling membrane over all the internal walls anyway so no issues there...

Strolling Bones

Have you considered attending one of these

Strolling Bones

PROJECT K wrote: »

Junction of plastered walls to stud frame walls:
This is where my first comment comes from - its almost inevitable that in any block house you will come across this type of junction (in my case framing to hide a pocket sliding door, suspended ceiling (edge of slab at landing for example), studding out to allow shower valves (cant recess these in a 100mm block wall!), framing out bulkheads etc etc). In a timber frame house all this would have been much easier and straigtforward. But im obviously stuck with what i have - the plasterer recommends overlapping the masonry component with the plasterboard by approx. 200-300mm to move the stress joints away from the actual junction, then use reinforcing skrim to protect this joint. I will have to then use an airtight membrane behind this and make sure this is also overlapped by the plaster and mesh. Also will have to use concrete screws rather than anchors to prevent air leakage. Any other ideas/experience on how to do this?

Thanks
PK

2 possibilties

1. parge the locations of the studs using Gyproc Airtite plaster first i.e. before erecting frames

2. staple a strip of AT membrane up the first stud before you fix it into position and use mesh to bond the plaster to it

BarneyMc

If you're getting someone in to do all of this they should be able to deal with everything you mention here. I've done this and got the installer to explain all just to be sure - it all makes sense and am happy he know's what he's doing (he does nothing else).

If not then attending a seminar as mentioned above would be a great idea. I'm sure the people selling tapes, membranes, etc. would be more than happy to explain all.

PROJECT K

Hi Sb, yes i have a few years ago (different supplier though) - probably need a refresher in fairness as back then i wasnt personally aware of the issues i am coming across now as part of the build process...what i find though is that the suppliers will supply any amounts of tape, adhesive, glue, primers etc etc and i wonder just how critical all of these are (in relation to my first post)

PROJECT K

BarneyMc wrote: »

If you're getting someone in to do all of this they should be able to deal with everything you mention here. I've done this and got the installer to explain all just to be sure - it all makes sense and am happy he know's what he's doing (he does nothing else).

If not then attending a seminar as mentioned above would be a great idea. I'm sure the people selling tapes, membranes, etc. would be more than happy to explain all.

Mines a DIY project Barney, got some quotes and due to the complexity of the build/details they were quite excessive. I have some time on my hands so can work on this while electrics/plumbing are being installed. Is your guy doing the plastering also? THis is where i have an issue as due to the esequencing of the work, there will be a huge overlap between the two processes...

BarneyMc

PROJECT K wrote: »

Mines a DIY project Barney, got some quotes and due to the complexity of the build/details they were quite excessive. I have some time on my hands so can work on this while electrics/plumbing are being installed. Is your guy doing the plastering also? THis is where i have an issue as due to the esequencing of the work, there will be a huge overlap between the two processes...

Fair play to you! My guy is just doing the airtightness stuff but is really good at explaining the sequencing options and will work around this for me.

Regarding timber frame v block... you made the right choice in my opinion. But we'll not open that can of worms today

PROJECT K

thanks Barney, can you pm his details?

rampantbunny

PROJECT K wrote: »

No barney, with the exception of one detail the rest are on the ground floor - in this house as is typical i am relying on the plaster as the airtight layer, but there are areas internally that abut external walls that are framed out etc so the strategy has to change to an airtight membrane with plasterboard. These issues are quite common, i am guessing most are just ignored and wont significantly impact on overall performance but thats the problem when you get too involved in the process!!! I have my ceiling membrane over all the internal walls anyway so no issues there...

Have you already fitted the stud work in place? Sounds like you have and it abuts the external block work in places - and this is the junction you want to seal?

I'm thinking of a stud walls at 90deg to external walls here.

If the stud walls are in place, without plasterboard, I'd consider using a mastic sealant around the joint/s where the timber meets the block work. Some/most of the AT product manufacturers provide a glue like substance to tape their membrane to the walls. It doesn't set hard, so will allow a certain amount of movement. Not sure if it will stick as well to timber however.
The timber itself will then be part of the airtight barrier, provided it is not peppered with holes.
Any junctions with horizontal timbers you can tape around. You mightn't have access to all the joints but better than none.

I'm doing the airtightness in my own house (block build) bit by bit, but don't have the same issues as you, so haven't had to think of the above.
I am at the moment, parge coating all those areas that will not be accessible after the metal ceiling goes on. Edges of plasterboard as you mentioned.

PROJECT K

rampantbunny wrote: »

Have you already fitted the stud work in place? Sounds like you have and it abuts the external block work in places - and this is the junction you want to seal?

I'm thinking of a stud walls at 90deg to external walls here.

If the stud walls are in place, without plasterboard, I'd consider using a mastic sealant around the joint/s where the timber meets the block work. Some/most of the AT product manufacturers provide a glue like substance to tape their membrane to the walls. It doesn't set hard, so will allow a certain amount of movement. Not sure if it will stick as well to timber however.
The timber itself will then be part of the airtight barrier, provided it is not peppered with holes.
Any junctions with horizontal timbers you can tape around. You mightn't have access to all the joints but better than none.

I'm doing the airtightness in my own house (block build) bit by bit, but don't have the same issues as you, so haven't had to think of the above.
I am at the moment, parge coating all those areas that will not be accessible after the metal ceiling goes on. Edges of plasterboard as you mentioned.

Thanks RB, no fortunately the stud work/framing isn't in as of yet - I'm just in the preparation stages, trying to get my head around the sequencing of it all!!!😊

rampantbunny

PROJECT K wrote: »

Thanks RB, no fortunately the stud work/framing isn't in as of yet - I'm just in the preparation stages, trying to get my head around the sequencing of it all!!!😊

Sequencing is key alright. There's a couple of places I didn't get to before they were covered over. Have to keep going though and just try to remediate as much as possible afterwards.

I had a few AT guys onsite before I started, and asked specifically when they'd need to come on site i.e. when would be early enough to make sure nothing was 'too late'. They would have missed the areas I've missed myself so I don't feel too bad when the experts didn't spot things either.

[Edit: so if your studs aren't in place, simplest thing is to just parge coat behind them. There's a pink plaster product available that is more airtight apparently than sand/cement (at same thickness). I've used sand/cement in places, and the pink stuff in others.]

PROJECT K

Yeah the guys i had missed a few areas too (also didnt allow for sequencing etc) so didnt inspire much confidence TBH. I knew i would have to be there every day to keep an eye on things so that was main reason for going DIY on this bit...also having guys in on a price to do this isnt ideal either, this job needs patience and time to do it right.

hexosan

If your looking for Airtightness products Ive just had mine shipped from a crowd in Germany and saved substantially over the prices here. Products were all pro clima.

PM me if you want the details.

PROJECT K

Thanks anyway Hexosan, have all materials sorted!

johnwstafford

hexosan wrote: »

If your looking for Airtightness products Ive just had mine shipped from a crowd in Germany and saved substantially over the prices here. Products were all pro clima.

PM me if you want the details.

Hi hexosan, would really appreciate if you fill me in also.....pm sent

Shelly2013

hexosan wrote: »

If your looking for Airtightness products Ive just had mine shipped from a crowd in Germany and saved substantially over the prices here. Products were all pro clima.

PM me if you want the details.

I would be very interested in these details if you don't mind sharing again. Will send PM

barryoc1

Strolling Bones wrote: »

Have you looked here

Strolling Bones, in relation to detail 1.20 on the link (warm flat roof build up) is there an airtight membrane required above the ceiling plasterboard for airtightness or is it sufficient to fit the plasterboard and skim finish? Sealing the joint between the plasterboard ceiling and the walls. In short, will plasterboard with a skim finish be sufficient to provide an airtight layer?

BryanF

barryoc1 wrote: »

Strolling Bones, in relation to detail 1.20 on the link (warm flat roof build up) is there an airtight membrane required above the ceiling plasterboard for airtightness or is it sufficient to fit the plasterboard and skim finish? Sealing the joint between the plasterboard ceiling and the walls. In short, will plasterboard with a skim finish be sufficient to provide an airtight layer?

Google 'vapour control layer'

barryoc1

BryanF wrote: »

Google 'vapour control layer'

I understand what a vapour control layer is but on the warm roof detail it shows the airtight layer being at ceiling level. The vapour control layer is under the insulation which is above the structure. So my query is whether another membrane is required above the ceiling to form the airtight layer or will the plasterboard with a skim finish suffice.

ht9zni1gs28crp

barryoc1 wrote: »

I understand what a vapour control layer is but on the warm roof detail it shows the airtight layer being at ceiling level. The vapour control layer is under the insulation which is above the structure. So my query is whether another membrane is required above the ceiling to form the airtight layer or will the plasterboard with a skim finish suffice.

I wouldn't rely on the Skim finish, trust me and my last 9 hours experience of chasing leaks to get from 1.01Ach down to 0.59

Simple motto, if any question on airtightness or doubt, get it membraned or sealed. You wouldn't believe the half of where leaks get it.

sami2015

hexosan wrote: »

If your looking for Airtightness products Ive just had mine shipped from a crowd in Germany and saved substantially over the prices here. Products were all pro clima.

PM me if you want the details.

Hi Hexosan,
could you please send me these details as well... I have just sent a pm. Thanks in advance - sami

hexosan

PM's sent

PROJECT K

barryoc1 wrote: »

I understand what a vapour control layer is but on the warm roof detail it shows the airtight layer being at ceiling level. The vapour control layer is under the insulation which is above the structure. So my query is whether another membrane is required above the ceiling to form the airtight layer or will the plasterboard with a skim finish suffice.

Airtightness is all about continuity - depending of course on your particular detail, getting your airtightness "line" on the walls joined up to the VCL above the flat roof deck would be a nightmare! I have a similar application where i used a bituminous vapour barrier under the flat roof insulation over a plywood deck. As the insulation is tapered (formed to falls) i placed additional insulation (mineral fibre) between the joists then used a humidity sensitive breathable airtight membrane underneath which can be easily sealed/taped/glued to the wall to ensure simple continuity. Take care if adopting a similiar strategy with insulation between joists as this could potentially cause interstitial condensation (i have average 200mm high performance insulation over the deck therefore not an issue in my case)

Regards
PK

PROJECT K

oh yes and plasterboard+skim is not 'airtight'!!!...:)

BarneyMc

rampantbunny wrote: »

I am at the moment, parge coating all those areas that will not be accessible after the metal ceiling goes on. Edges of plasterboard as you mentioned.

I'm coming to this stage now and not sure I understand this. Is this not the right sequence?

1. Apply airtight tapes etc.
2. Plaster walls
3. Install metal ceiling
4. Install ceiling plasterboard
5. Skim ceiling plasterboard and plastered walls

rampantbunny

BarneyMc wrote: »

I'm coming to this stage now and not sure I understand this. Is this not the right sequence?

1. Apply airtight tapes etc.
2. Plaster walls
3. Install metal ceiling
4. Install ceiling plasterboard
5. Skim ceiling plasterboard and plastered walls

Sequence can differ Barney. My electrician wanted metal ceilings in for his first fix (to run cables), therefore my walls weren't plastered before ceilings were installed.

ht9zni1gs28crp

Have you timber joists or conc slab for floor?

The electrician here has tricky sequence, he needs to work with you on the Airtight as does the plasterer. The point where the wires exit the chase into the suspended ceiling needs to be air sealed to the best you can. Access can prove tricky to do the job correctly.

If I was approaching it again this time I would leave the suspended ceiling until after airtight test. If this means the Electrician has to temp tack wires to U/S of floor I would do as it means your chasing can be plastered over. It means you or your plasterer has good access to ensure the chases are filled at the top point.

BarneyMc

rampantbunny wrote: »

Sequence can differ Barney. My electrician wanted metal ceilings in for his first fix (to run cables), therefore my walls weren't plastered before ceilings were installed.

OK, where exactly do your cables run? I've never seen the metal suspended ceiling in the flesh. What depth was your suspended ceiling?

My cables are tied up to the underside of the concrete slab so not sure how it will work putting the suspended ceiling on now???

ht9zni1gs28crp

If your cables are chased vertically and tied to U/S of slab then I would aim at sealing these and getting the vertical internal walls plastered first. Yes it means two visits for the plasterer but in this new age game they are going to have to get used to two stage plastering. Don't close off ceiling until first airtest is run...

rampantbunny

BarneyMc wrote: »

OK, where exactly do your cables run? I've never seen the metal suspended ceiling in the flesh. What depth was your suspended ceiling?

My cables are tied up to the underside of the concrete slab so not sure how it will work putting the suspended ceiling on now???

Sorry Barney, meant to take a photo this evening but completely forgot. Here's what it looks like before slabbing: link

Before any wall chasing was done, I marked the approximate point where the metal ceilings would be. I told the electrician to chase to just above the metal ceiling line. He'd only need enough room to slide cables down into conduit so no point chasing all the way to hollowcore.

I had 'wrapped' my hollowcore, so to tie it into the internal leaf I ran expanded metal.
When chases done I applied (well my plasterer applied) the pink airtight plaster to cover the expanded metal and wrap, and ran it down just past the metal ceiling line making sure to apply some to the top of the wall chases.

Metal ceiling guy came and installed ceiling. Electrician came back and ran all his cables across the metal ceiling 'lattice' and down the vertical chases.
As for your electrician tying the cables to the underside of the slab...ROFL...no way that mine would be doing that. He needed an excuse to leave the site to take on 5 other jobs and when ceilings weren't in, he was out of there. Much simpler on your build.

ht9zni1gs28crp

rampantbunny wrote: »

Sorry Barney, meant to take a photo this evening but completely forgot. Here's what it looks like before slabbing: link

Before any wall chasing was done, I marked the approximate point where the metal ceilings would be. I told the electrician to chase to just above the metal ceiling line. He'd only need enough room to slide cables down into conduit so no point chasing all the way to hollowcore.

I had 'wrapped' my hollowcore, so to tie it into the internal leaf I ran expanded metal.
When chases done I applied (well my plasterer applied) the pink airtight plaster to cover the expanded metal and wrap, and ran it down just past the metal ceiling line making sure to apply some to the top of the wall chases.

Metal ceiling guy came and installed ceiling. Electrician came back and ran all his cables across the metal ceiling 'lattice' and down the vertical chases.
As for your electrician tying the cables to the underside of the slab...ROFL...no way that mine would be doing that. He needed an excuse to leave the site to take on 5 other jobs and when ceilings weren't in, he was out of there. Much simpler on your build.

So what did the Electrician use to close off the top of the chase then? If the electrician was in after the plasterer? It renders all the previous airtight work a waste of time if nothing was used. you airtight test will just fill the suspended ceiling with draughts making it impossible to find any leaks.

rampantbunny

miller_63 wrote: »

So what did the Electrician use to close off the top of the chase then? If the electrician was in after the plasterer? It renders all the previous airtight work a waste of time if nothing was used. you airtight test will just fill the suspended ceiling with draughts making it impossible to find any leaks.

Read carefully:

rampantbunny wrote: »

When chases done I applied (well my plasterer applied) the pink airtight plaster to cover the expanded metal and wrap, and ran it down just past the metal ceiling line making sure to apply some to the top of the wall chases.

Top of chase = airtight plaster
If you meant top of conduits...I've put mastic at these locations even though I think it isn't necessary.

BarneyMc

miller_63 wrote: »

Simple motto, if any question on airtightness or doubt, get it membraned or sealed. You wouldn't believe the half of where leaks get it.

My airtightness guy is adamant I don't need to apply membrane on the marine ply around my window reveals. I'm sure he's right as he's really experienced in this field and my initial blower test will reveal any leaks anyway. However, my worry is in x years time it may not hold up. Should I just ask him to membrane it anyway just for peace of mind if nothing else? :cool:

hexosan

I membraned mine. It doesn't take that long to do it and since you've to tape the ply anyway it doesn't cost a whole lot more.

ht9zni1gs28crp

BarneyMc wrote: »

My airtightness guy is adamant I don't need to apply membrane on the marine ply around my window reveals. I'm sure he's right as he's really experienced in this field and my initial blower test will reveal any leaks anyway. However, my worry is in x years time it may not hold up. Should I just ask him to membrane it anyway just for peace of mind if nothing else? :cool:

How many of these exact ply reveal details has he done? There is air in the cavity so what material is going onto the ply board, as in what size insulated plasterboard? A complete membrane from window unit back to the block is vital, other wise you are relying on the plasterer to get his corner bead exactly perfect 100% of the time along with the Ply board being totally airtight with no fixings in it.

Maybe show us your drawings of the jamb and head details?

PROJECT K

miller_63 wrote: »

...A complete membrane from window unit back to the block is vital...

I don't believe it is, if the ply is a decent quality marine ply it will be sufficiently airtight - the windows are taped onto the ply, the ply is taped onto the blockwork and the fixing holes are taped over (therefore not dependant on plaster to make these connections). Fix expanded metal with small slab nails and plaster over (which effectively provides a secondary airtight layer). Applying a membrane that you will have to puncture with fixings anyway will provide very little extra resistance against air leakage. The difficulty associated with trying to get a membrane dressed neatly into corners etc and taped onto the windows is unnecessary. Also the fact that there is air in the cavity means very little - air is all around these details - once an airtight layer is formed external air cavities shouldn't impact in any way...

This has been a standard detail to achieve airtightness and has been proven to work many times over - why complicate the detail with additional membrane?

BarneyMc

PROJECT K wrote: »

I don't believe it is, if the ply is a decent quality marine ply it will be sufficiently airtight - the windows are taped onto the ply, the ply is taped onto the blockwork and the fixing holes are taped over (therefore not dependant on plaster to make these connections).

This is exactly what my airtightness guy suggests. He said he can then 'glue' insulated plasterboard to the ply (there is a bit of space from the ply to the window frame so will bridge the gap with insulated plasterboard) whereas if there was membrane there then he would have to nail it which would not be great I suppose.

My only concern is over time will the marine ply crack, etc.?

PROJECT K

"My only concern is over time will the marine ply crack, etc.? "

I doubt very much that it would, and even if it did it would be most likely around the fixing locations so I would tape these generously. The ply generally isn't under any significant stresses in this application - I have seen marine ply used in external applications with render cover and never any issues...

ht9zni1gs28crp

That's fine if you trust the Ply to be totally airtight. I'm thinking more a practical solution and what worked well for me from experience which incidentally achieved 0.6ACH.

In effect you are doubling your workload and amount of taping doing it that way, for what saving maybe 100mm of membrane? You will also end up taping the corners of the ply too where the jamb board meets the head/cill etc. By the time you have finished a single piece of pre cut membrane say 200mm wide would have looked an easier more foolproof option,this is taped to the frame and taped back to the block. Leave enough slack to staple the membrane to the ply tightly in order for the insulated board to be fitted snugly.

The less taping and jointing you need the better IMHO.

BarneyMc

miller_63 wrote: »

That's fine if you trust the Ply to be totally airtight. I'm thinking more a practical solution and what worked well for me from experience which incidentally achieved 0.6ACH.

In effect you are doubling your workload and amount of taping doing it that way, for what saving maybe 100mm of membrane? You will also end up taping the corners of the ply too where the jamb board meets the head/cill etc. By the time you have finished a single piece of pre cut membrane say 200mm wide would have looked an easier more foolproof option,this is taped to the frame and taped back to the block. Leave enough slack to staple the membrane to the ply tightly in order for the insulated board to be fitted snugly.

The less taping and jointing you need the better IMHO.

Really appreciate your thorough answer but leaves me with my initial dilemma again.

Can I just ask how you fixed the insulated plasterboard - nails? And did you have any air leakage on your initial blower test with this?

petesy38

miller_63 wrote: »

That's fine if you trust the Ply to be totally airtight. I'm thinking more a practical solution and what worked well for me from experience which incidentally achieved 0.6ACH.

In effect you are doubling your workload and amount of taping doing it that way, for what saving maybe 100mm of membrane? You will also end up taping the corners of the ply too where the jamb board meets the head/cill etc. By the time you have finished a single piece of pre cut membrane say 200mm wide would have looked an easier more foolproof option,this is taped to the frame and taped back to the block. Leave enough slack to staple the membrane to the ply tightly in order for the insulated board to be fitted snugly.

The less taping and jointing you need the better IMHO.

Some pics to illustrate would be helpful!!

BarneyMc

A big plus if not going the membrane route is not having to nail the insulated plasterboard to the ply. My airtightness guy can simply glue it. Even though nails/screws 'fill their own hole' it would be nice not to have to pierce.

BarneyMc

Anyone with other opinions on this?

rampantbunny

BarneyMc wrote: »

Anyone with other opinions on this?

I've put membrane around the window reveals/head/sill.
I stapled this in place to the marine ply (staples do not go all the way through the marine ply). I need to finish off by taping the joint between window frame and membrane and back to block work also.
My windows have to be 'squared up' which means bonding needs to be applied before plasterboard is fitted. The plasterboard can adhere to this bonding, but I may still need a screw or two.
Need to see how it works onsite before knowing if I can get away without screws entirely.

galwaytt

BarneyMc wrote: »

A big plus if not going the membrane route is not having to nail the insulated plasterboard to the ply. My airtightness guy can simply glue it. Even though nails/screws 'fill their own hole' it would be nice not to have to pierce.

....although not quite the same, and we use OSB3, screws don't leak at the pressures we're talking about in a house - it's not a pressure cylinder we're building here folks.............

Just had the result of a preliminary blower test back on recent build at first fix, and pre installation of any plasterboard to walls or ceilings - 0.49 ACH. I'll be interested to see what happens that number once it's finished out.

rampantbunny

galwaytt wrote: »

....although not quite the same, and we use OSB3, screws don't leak at the pressures we're talking about in a house - it's not a pressure cylinder we're building here folks.............

Just had the result of a preliminary blower test back on recent build at first fix, and pre installation of any plasterboard to walls or ceilings - 0.49 ACH. I'll be interested to see what happens that number once it's finished out.

Do you expect the figure to increase/worsen?

BarneyMc

rampantbunny wrote: »

I've put membrane around the window reveals/head/sill.
I stapled this in place to the marine ply (staples do not go all the way through the marine ply). I need to finish off by taping the joint between window frame and membrane and back to block work also.
My windows have to be 'squared up' which means bonding needs to be applied before plasterboard is fitted. The plasterboard can adhere to this bonding, but I may still need a screw or two.
Need to see how it works onsite before knowing if I can get away without screws entirely.

So you're going the membrane route just in case the ply doesn't stand up to the airtightness test?