Airtightness tape around windows

springer111

Hi everyone

Just wondering if any one can advice me on this.

I have airtightness tape ready to fit around me newly installed Windows (block new build) only there are hollows between the fitting straps for the Windows and the cavity closers and blocks. This is due to window straps fitted at an angle because of gaps around the Windows. Have filled gaps around Windows with expanding foam. Will I foam in behind the window straps so the airtightness tape will have something to stick on to???

Sorry if that is hard to understand 😬😬

893bet

Picture would help?

Also ensure you are using the correct tape. Each brand has 10 or 15 for different applications.

springer111

If you google " prodomo sealing window gaps" it's like the first pic only not as extreme. See if I run tape along down the side of the window the straps prevent it sticking to the cavity closer and blocks. Should I fill gap with expanding foam out as far as the straps?? At least it would be sticking to something then??

rampantbunny

springer111 wrote: »

Hi everyone

Just wondering if any one can advice me on this.

I have airtightness tape ready to fit around me newly installed Windows (block new build) only there are hollows between the fitting straps for the Windows and the cavity closers and blocks. This is due to window straps fitted at an angle because of gaps around the Windows. Have filled gaps around Windows with expanding foam. Will I foam in behind the window straps so the airtightness tape will have something to stick on to???

Sorry if that is hard to understand 😬😬

Apply some airtightness tape over the actual strap from the window to where it meets the cavity closer. Continue the tape past the end of the strap itself and make sure each side of the strap is also well covered.

If nails are proud of the strap hammer them in etc.

springer111

rampantbunny wrote: »

Apply some airtightness tape over the actual strap from the window to where it meets the cavity closer. Continue the tape past the end of the strap itself and make sure each side of the strap is also well covered.

If nails are proud of the strap hammer them in etc.

Many thanks. If I taped the straps and then used the expanding foam and trim at window straps. At least tape will be better stuck to something between the straps??

Or is that pointless

rampantbunny

springer111 wrote: »

Many thanks. If I taped the straps and then used the expanding foam and trim at window straps. At least tape will be better stuck to something between the straps??

Or is that pointless

OK, will def. need a pic now. Sorry don't know what you mean by 'better stuck to something between the straps'. The tape should be wide enough to cover the strap itself and then stick to the cavity closer, not to what is under the strap i.e. foam in your case.

The way I imagine it, depending on the height of your windows you have maybe 3 straps which come (at an angle) from the side of your window frame back to your cavity closer. Lets say the cavity closer is the old fashioned block.

You were thinking about putting foam between the window frame and the adjacent cavity closer. Go ahead; the foam will not be your primary airtightness barrier but it can't hurt* even if foam is 'supposed' to degrade over time.
I caveat the word 'hurt' because it is possible to do damage if the expanding foam forces your window frames to bow - therefore, avoid using too much foam and better again, use a low expansion foam.

No point putting foam behind the straps (not sure how you would even manage it). Is the strap at that much of an angle that it will take the nozzle of a foam gun?

Just tape over the strap like I said previously. How are you working your way around the window? What is the rest of your detail?
On my build I applied AT membrane all the way around the reveals, cill, head, which covered all my straps. But I taped over the straps also so that rough edges and nail heads wouldn't puncture the membrane.

springer111

rampantbunny wrote: »

OK, will def. need a pic now. Sorry don't know what you mean by 'better stuck to something between the straps'. The tape should be wide enough to cover the strap itself and then stick to the cavity closer, not to what is under the strap i.e. foam in your case.

The way I imagine it, depending on the height of your windows you have maybe 3 straps which come (at an angle) from the side of your window frame back to your cavity closer. Lets say the cavity closer is the old fashioned block.

You were thinking about putting foam between the window frame and the adjacent cavity closer. Go ahead; the foam will not be your primary airtightness barrier but it can't hurt* even if foam is 'supposed' to degrade over time.
I caveat the word 'hurt' because it is possible to do damage if the expanding foam forces your window frames to bow - therefore, avoid using too much foam and better again, use a low expansion foam.

No point putting foam behind the straps (not sure how you would even manage it). Is the strap at that much of an angle that it will take the nozzle of a foam gun?

Just tape over the strap like I said previously. How are you working your way around the window? What is the rest of your detail?
On my build I applied AT membrane all the way around the reveals, cill, head, which covered all my straps. But I taped over the straps also so that rough edges and nail heads wouldn't puncture the membrane.

Sorry I'm too much of a newbie to post pics. Ya gaps behind straps are around 1 inch. I think I'll follow your advice. Just wrap the straps and then tape from window in to the block

rampantbunny

springer111 wrote: »

Sorry I'm too much of a newbie to post pics. Ya gaps behind straps are around 1 inch. I think I'll follow your advice. Just wrap the straps and then tape from window in to the block

That is a substantial gap. Mine would have a max if maybe 3mm.

If you wanted to save tap, cut some sections of AT membrane and just tape it over the strap. You won't feel going through roll of tape covering those straps.

Are you putting insulated plasterboard around the reveals?

springer111

rampantbunny wrote: »

That is a substantial gap. Mine would have a max if maybe 3mm.

If you wanted to save tap, cut some sections of AT membrane and just tape it over the strap. You won't feel going through roll of tape covering those straps.

Are you putting insulated plasterboard around the reveals?

Sorry I'm a bit of a novice at this. Was going using the siga fentrim tape all around Windows. I know we are doing 62.5 insulated slab but I don't know about the reveals. How would that fit?

rampantbunny

springer111 wrote: »

Sorry I'm a bit of a novice at this. Was going using the siga fentrim tape all around Windows. I know we are doing 62.5 insulated slab but I don't know about the reveals. How would that fit?

Because my cavity closers are very close to my window frames, my straps are pretty straight. I can put standard plasterboard (not insulated) over these and plaster over.

With a gap like yours, the cavity closer must be back from your window frame a good bit. An insulated plasterboard could be fitted to the reveals.
Where the insulated board meets the straps, you'd have to rebate/notch the insulated backing to allow room for the strap to run behind. Your insulated board would be nice and flat against your cavity closer regardless of the angle of your straps.

You wouldn't be using 62.5mm board around the windows. Something slimmer would be needed. Have you a builder/contractor onsite or is this your own self-build?

springer111

rampantbunny wrote: »

Because my cavity closers are very close to my window frames, my straps are pretty straight. I can put standard plasterboard (not insulated) over these and plaster over.

With a gap like yours, the cavity closer must be back from your window frame a good bit. An insulated plasterboard could be fitted to the reveals.
Where the insulated board meets the straps, you'd have to rebate/notch the insulated backing to allow room for the strap to run behind. Your insulated board would be nice and flat against your cavity closer regardless of the angle of your straps.

You wouldn't be using 62.5mm board around the windows. Something slimmer would be needed. Have you a builder/contractor onsite or is this your own self-build?

Thanks for your reply. Yes it's our own self build. We have a builder alright, it's a family member so have the option to do some things ourselves

Option 1
So could I get say a 25mm rigid insulation boards, apply to reveals and notch out for the straps. Then apply siga fentrim tape from window frame back to block and let the guys slabbing finish it off with ordinary plasterboard

It option 2
Just get an insulated plaster board and fit that. I presume I can get a tape to go over that. One that can take the plaster after. The tape with the holes??

I think option 1 is easier for me. Being a woman I'd probably find the cutting of the rigid insulation easer than the insulated slab ;-)

Does this sound like a good option so? I know more expense with insulation but you can never have enough of that right??

Thanks

rampantbunny

springer111 wrote: »

Thanks for your reply. Yes it's our own self build. We have a builder alright, it's a family member so have the option to do some things ourselves

Option 1
So could I get say a 25mm rigid insulation boards, apply to reveals and notch out for the straps. Then apply siga fentrim tape from window frame back to block and let the guys slabbing finish it off with ordinary plasterboard

It option 2
Just get an insulated plaster board and fit that. I presume I can get a tape to go over that. One that can take the plaster after. The tape with the holes??

I think option 1 is easier for me. Being a woman I'd probably find the cutting of the rigid insulation easer than the insulated slab ;-)

Does this sound like a good option so? I know more expense with insulation but you can never have enough of that right??

Thanks

It all depends how proud the straps are from the cavity closer...you'll have to work this out and get insulation to suit. Just be mindful that if you go too thick with the insulation, you could end up encroaching on your window frame more than you might like i.e. you might end up covering too much of your frame.

You could also buy the insulation affixed to the plasterboard...I don't have any on my build at all, but think it comes in thicknesses like 32.5mm, 37.5, 52.5 etc...

You should apply the airtight tapes from window to blockwork first (and over straps like mentioned above).
The remainder of the cavity closer (if block) is not in itself airtight. This can be made airtight by parge coating (thin layer of plaster). Install the insulation. You could do all this work yourself if you want to save money, and afterwards get the guys slabbing to install the plasterboard. Or, if you want to save time, get the guys slabbing to install insulated plasterboard telling them to notch the insulation over the straps.

An alternative to parge coating the block is to tape AT membrane to the window, and run it over the straps and into your inner leaf blockwork. Work involved here too, but only requires tapes and membrane as opposed to trowel and plaster.

I'm not familiar with the Siga tapes, but you just need to make sure what you get is suitable for the window junction and will stick to blockwork. I think you'll need to buy a 'mastic' to apply to the block work before you'll be able to stick the tape to it.

[Edit]
I'm not sure applying tape to plasterboard and then skimming over that is the done thing for airtightness. Doesn't sound right to me. Tape to the blockwork.

893bet

Take a photo and upload from your phone.

Here is what my windows looked like after taping. A few of the straps were proud but nothing major. 10-15 cm at most. I just covered them with tape. The plastered built out the reveal with bonding and applied the slab then.

rampantbunny

893bet wrote: »

Take a photo and upload from your phone.

Here is what my windows looked like after taping. A few of the straps were proud but nothing major. 10-15 cm at most. I just covered them with tape. The plastered built out the reveal with bonding and applied the slab then.

10-15cm...your plasterer did well to hide that

springer111

893bet wrote: »

Take a photo and upload from your phone.

Here is what my windows looked like after taping. A few of the straps were proud but nothing major. 10-15 cm at most. I just covered them with tape. The plastered built out the reveal with bonding and applied the slab then.

Boards.ie says I'm not allowed post a picture because I'm still considered New user??

rampantbunny

If it's an inch as you said it was behind the strap then I can't see a plasterer building up that much..even 15mm+ is a decent amount.
Installing insulated plasterboard also helps combat the cold bridge at the window reveal.

If all the reveals are the same amount back from the window frame you could angle your standard non-insulated plasterboard back, just as the straps are angled. This can look nice and give the impression that the window is wider than it actually is.
That's if you don't mind the cold bridge without the insulated board.

893bet

rampantbunny wrote: »

10-15cm...your plasterer did well to hide that

That was at the very most and only the odd one. Most were flat.

I notice a few friends building who went with a certain notorious Munster based company with massive gaps around windows. Seem to be allowing far too much.

rampantbunny

893bet wrote: »

That was at the very most and only the odd one. Most were flat.

I notice a few friends building who went with a certain notorious Munster based company with massive gaps around windows. Seem to be allowing far too much.

Don't think you spotted it but you're using cm instead of mm (I hope)..
Surprised at you 893bet..coming from a self build you know the devil is in the detail, and there are details everywhere

BryanF

springer111 wrote: »

Thanks for your reply. Yes it's our own self build. We have a builder alright, it's a family member so have the option to do some things ourselves

Option 1
So could I get say a 25mm rigid insulation boards, apply to reveals and notch out for the straps. Then apply siga fentrim tape from window frame back to block and let the guys slabbing finish it off with ordinary plasterboard

It option 2
Just get an insulated plaster board and fit that. I presume I can get a tape to go over that. One that can take the plaster after. The tape with the holes??

I think option 1 is easier for me. Being a woman I'd probably find the cutting of the rigid insulation easer than the insulated slab ;-)

Does this sound like a good option so? I know more expense with insulation but you can never have enough of that right??

Thanks

Option 1 - BUT Put a base layer of plaster on the block work, so that this is your air-tightness layer throughout the house, watch sockets/penetrations in this plastered block layer, as block is porous!. Once block has a plaster coat, you tape from window to plaster and then add either plaster, sealant or tape depending on product to form the air-tight seal (refer to the product data sheet), then add your insulated plasterboard assuming there is adequate insulation outside the air-tightness membrane (so that its is in fact acting as a vapour barrier). Too much drylining may bring the due point inside the air-tightness later, which you don't want.

Edit: IMO and based on your posts in this thread,
1. you would benifet from an air-tightness course( this is just one day and not very expensive, just google, they are on regularly)
2. Stop, and look at all of the envelope and work out the air-tightness strategy and where this needs to happen at every location in the external envelope. Perhaps get some assistance from either your architect or an air-tightness tester - which you should be getting to check you comply with building regs, but really to figure out the finer leakage points.
3. Check you provisional BER and the proposed:air-tightness, Mvhr requirements, renewables and thermal bridge factor etc.

THE DON FANUCCI

What does it mean to use a return block at window reveals? and if I have a pumped bead cavity how does this affect sealing my windows with tape?

dathi

THE DON FANUCCI wrote: »

What does it mean to use a return block at window reveals?

it means who ever drew up your plans is about 10 years out date

fatty pang

dathi wrote: »

it means who ever drew up your plans is about 10 years out date

…. or is simply cognisant of the difficulties in getting somebody (who knows what they are at) to stand over a window/door anchor fixing into the 100mm wide face of a block ‘on edge’.
I’m all for minimising cold-bridges, but at the risk of being deemed old-fashioned, I would maintain that structural integrity comes first.

BryanF

fatty pang wrote: »

…. or is simply cognisant of the difficulties in getting somebody (who knows what they are at) to stand over a window/door anchor fixing into the 100mm wide face of a block ‘on edge’.
I’m all for minimising cold-bridges, but at the risk of being deemed old-fashioned, I would maintain that structural integrity comes first.

I'm all for 1:5 details of this particular window

fatty pang

BryanF wrote: »

I'm all for 1:5 details of this particular window

Nothing new - closer block.
My preferred choice would be a Cavalok structural cavity closer. Facilitates direct fixing (advisable for doors in particular) and acts as a former, minimising the chance of a cock-up by brickies. Oh... and it's thermally pretty good as well.

ht9zni1gs28crp

Its really hard to start the onerous task of advising people when even the basic details and strategy hasn't been sorted.

I'm sorry to say its destined not to be the best you could have achieved.....

ht9zni1gs28crp

.......

MacConmhaigh

Hi guys, has anyone got any pictures of applying siga corvum pre folded tape to windows for airtightness?

BryanF

MacConmhaigh wrote: »

Hi guys, has anyone got any pictures of applying siga corvum pre folded tape to windows for airtightness?

Yes
The manufacturer

Tigerandahalf

Instead of opening a new thread where could I get a felt weatherstrip to put around a front door frame to stop a small draught. Door isn't closing fully square but I think this would be the best option.

Thanks

Can anybody advise the best way to seal this from an air tightness point of view. There is an 8 inch cavity. I have the pro clima tapes, but will i also need to use air tightness membrane across this cavity ?

How is this then finished, is plasterboard glued on ?


IMG_20171007_130605.jpg

MacConmhaigh

[Deleted User] wrote: »

Can anybody advise the best way to seal this from an air tightness point of view. There is an 8 inch cavity. I have the pro clima tapes, but will i also need to use air tightness membrane across this cavity ?

How is this then finished, is plasterboard glued on ?

Possibly two roles of airtightness tape over lapped,?? Depends on plasterer, some use bonding first and some use plasterboard! Get onto your engineer and plasterer.

MacConmhaigh

MacConmhaigh wrote: »

Possibly two roles of airtightness tape over lapped,?? Depends on plasterer, some use bonding first and some use plasterboard! Get onto your engineer and plasterer.

Unfortunately to my cost my engineer is barely able to advise on building a chicken coop, and the plasterer will do what ever is quickest.

The tape would be too narrow to just double lap.

MacConmhaigh

MacConmhaigh wrote: »

Possibly two roles of airtightness tape over lapped,?? Depends on plasterer, some use bonding first and some use plasterboard! Get onto your engineer and plasterer.

Try this so, staple a dpc to a length of ply and square up all window reveals with it. Then screw your plaster board onto it and put airtight tape around that. Plus on outer most ply to wrap it around.
Alternatively employ another engineer or an airtighness company to do it all for you.

MacConmhaigh

MacConmhaigh wrote: »

Try this so, staple a dpc to a length of ply and square up all window reveals with it. Then screw your plaster board onto it and put airtight tape around that. Plus on outer most ply to wrap it around.
Alternatively employ another engineer or an airtighness company to do it all for you.

Will this not rot over time ?

MacConmhaigh

MacConmhaigh wrote: »

Try this so, staple a dpc to a length of ply and square up all window reveals with it. Then screw your plaster board onto it and put airtight tape around that. Plus on outer most ply to wrap it around.
Alternatively employ another engineer or an airtighness company to do it all for you.

I found an image similar to what you describe. But would it now be possible for cool air to travel between the PIR board and the plywood to the inside cavity ? Or is there a type of plasterboard i could use instead of the plywood ?

In my case above if i use plywood is it not making the PIR completely redundant i.e. i could take it out and just let the bead come flush to the back of the plywood ??

listermint

You put Ply over the top, covering the gap.

Once in you tape the outer corner joint with SL Contega Tape. Solida, You can also use that on the inner joint Window to plywood. You dont need to use the teson stuff Contega will do both.

Finally plasterboard over the top and plasterer to finish.

Done.

I assume the Plywood would be fixed to the internal leaf only, what would you suggest to do that i.e. just screws and wall plugs

I would have to make a channel in the ply to fit over the window straps(as shown in the image of the previous page https://www.boards.ie/vbulletin/attachment.php?attachmentid=430078&d=1507494123). There would likely be a gap between the ply and the PIR should i put something here or would it be better to remove the existing PIR and let the bead come right up to the back of the ply ?

listermint

Use multifix concrete screws they are handiest to fix in. You don't need to channel out the strap it's flush.

Don't over think this. Ply tape plasterboard. Done

dfader

[Deleted User] wrote: »

Can anybody advise the best way to seal this from an air tightness point of view. There is an 8 inch cavity. I have the pro clima tapes, but will i also need to use air tightness membrane across this cavity ?

How is this then finished, is plasterboard glued on ?


IMG_20171007_130605.jpg

Why not just,
1. Clean up excess foam with knive
2. Tape window to insulation with siga fentrim or similar
3. Expanded mesh over whole lot back to block
4. Sand cement render over as airtight layer.

Don't see the need for plywood box now that the windows are strapped in. Ply box would have been good to close cavity prior to window installation.