Airtight around windows

Curious Geroge

I'm hoping someone may be able to help me re a query on the detail on application of the tape around the windows.

I'm in the process of application and using the Corvum tape from a well known supplier (not to mention suppliers) but I would ask if anyone that has used this around the window can tell me if the plasterer can plaster on top of this tape or should I be placing plasterboard on this and having the plasterer plaster that. The demo videos are always shown on timber frame houses.

Another question on the DPC line that comes up from the bottom of the window and application of tape. How have you done it ? The DPC comes up at the inside of the window, but what to do re the airtight here ?

bertie 56

Curious Geroge wrote: »

I'm hoping someone may be able to help me re a query on the detail on application of the tape around the windows.

I'm in the process of application and using the Corvum tape from a well known supplier (not to mention suppliers) but I would ask if anyone that has used this around the window can tell me if the plasterer can plaster on top of this tape or should I be placing plasterboard on this and having the plasterer plaster that. The demo videos are always shown on timber frame houses

As said in a previous post, the best product for skimming on top would have been the Fentrim, from the same brand :
http://www.boards.ie/vbulletin/showthread.php?p=89508634 :rolleyes:

I've used the Corvum all right, but in a timber frame ... :P
I wouldn't trust to stick some plaster on top, it's kind of smooth.
The Fentrim has some " hair " outside , made to stick with the plaster.

Now, if the job is already done, I would recommend you to cover it with some plasterboard before skimming.

Whatever the tape, the problem in general with skimming strait away is that you usually don't have enough tape in the window, unless you put a big thickness of plaster. Fitting a layer ( or two) of plasterboard allow you to have a good width of tape stick in the window frame, which is what is important for airtightness.
( I don't know if this explanation is clear ? )

Curious Geroge

bertie 56 wrote: »

As said in a previous post, the best product for skimming on top would have been the Fentrim, from the same brand :
http://www.boards.ie/vbulletin/showthread.php?p=89508634 :rolleyes:

I've used the Corvum all right, but in a timber frame ... :P
I wouldn't trust to stick some plaster on top, it's kind of smooth.
The Fentrim has some " hair " outside , made to stick with the plaster.

Now, if the job is already done, I would recommend you to cover it with some plasterboard before skimming.

Whatever the tape, the problem in general with skimming strait away is that you usually don't have enough tape in the window, unless you put a big thickness of plaster. Fitting a layer ( or two) of plasterboard allow you to have a good width of tape stick in the window frame, which is what is important for airtightness.
( I don't know if this explanation is clear ? )

Thanks Bertie; If I'm honest I had the Fentrim also but the lip was 20mm while the Corvum lip was 10mm and the 10mm on the window frame seemed much easier to hide with a single plasterboard surround. I was just looking for confirmation that the plasterboard is used by everyone (commonly) once the window is taped.

Curious Geroge

Curious Geroge wrote: »

Another question on the DPC line that comes up from the bottom of the window and application of tape. How have you done it ? The DPC comes up at the inside of the window, but what to do re the airtight here ?

Would anyone be able to supply detail on how they dealt with the DPC ?

bertie 56

Curious Geroge wrote: »

Thanks Bertie; If I'm honest I had the Fentrim also but the lip was 20mm while the Corvum lip was 10mm and the 10mm on the window frame seemed much easier to hide with a single plasterboard surround. I was just looking for confirmation that the plasterboard is used by everyone (commonly) once the window is taped.

Ok, I got it. The Corvum I've used is the 30/30, the square one , it's 30 x 30 mm. ( I put timber lining myself, quite close to the glass of the window so the tape is hidden )
The one you are talking about is the 12/48, I suppose , and the small lip is 12 mm . So, yes, easier to hide.

The Fentrim has a lip of 15 mm , so it's still OK to do with one layer of 12.5 plasterboard + 3/4 mm of skimming.
But it depends as well of the width of the foam between your blocks and the window frame .


About the DPC , I think you have nothing to do much about it for airtighness , just be sure that your tape sticks in your blocks in one side, and in the window frame the other side. It's my own opinion, please take advice with other people for this point.( A picture will help)

Curious Geroge

Just to be sure we're on the right track, I've attached some of the finished windows from today. Should anyone spot any issues with the application of the tape you might let me know.

2014-04-01 14.04.35.jpg

2014-04-01 14.06.19.jpg

2014-04-01 14.08.55.jpg

2014-04-01 14.05.32.jpg

2014-04-01 14.06.01.jpg

Curious Geroge

A couple of possible difficult one's tomorrow. Can anyone recommend how to airtight seal a corner window as shown.

2014-04-01 14.06.26.jpg

Also, the window installer had to add timber and I wondered how best to finish this ?

2014-04-01 14.06.36.jpg

esox28

George hey, don't get me wrong im not criticizing the taping but if your serious about airtightness your approch won't give a good result as it stands.
You ask wheather skim will go straight on to the reviels...well I wouldent for two reasons,first is the skim will crack at the window intersection with the tape, using bonding first may over come this if built out before skimming, secondly you have about 15mm taped to the window frame which will be seen if only using skim at a depth of 4-5mm.

What I think you need to do is start again.

as you have a block reviel right up to frame, I would get the reviels plastered with a smooth finish sand/cement then tape frame to plastered reviel.

When window are all taped up then plaster in the edge of the tape to the plaster with some bonding, just for extra protection.

Fit your 12.5mm plaster board for reviels and leave a protruding edge of 10mm for the plasterer to meet with sand and cement gray coat from wall.

esox28

Curious Geroge wrote: »

A couple of possible difficult one's tomorrow. Can anyone recommend how to airtight seal a corner window as shown.

2014-04-01 14.06.26.jpg

Also, the window installer had to add timber and I wondered how best to finish this ?

2014-04-01 14.06.36.jpg

Tape window to steel prop, you will need to box it in after.

second pic... Add another 2x2 Batton, smooth plaster the wall or use sealent but in any case use a membrane to wrap the timber from window to blockwork, tape frame to membrane and tape or stick membrane to wall. Then using your plaster board to finish the reviels but screw to timber sparingly.

declan52

You can use a bit of skim to give you a 40mm strip of a smooth band against frame. Make it wider if your tape that goes against the block work is bigger. This gives you a smooth surface to stick tape to. Some companies recommend using a mastic to stick to blockwork to fill out the roughness leaving no gaps. Then plaster over as normal or scratch it and use plasterboard up to you. As previous post says have to be carefull how much tape you have on the frame.

BryanF

Curious Geroge wrote: »

Just to be sure we're on the right track, I've attached some of the finished windows from today. Should anyone spot any issues with the application of the tape you might let know]

shouldnt your architect details & air-tightness tester be 'spotting' these things?:o

Curious Geroge

BryanF wrote: »

shouldnt your architect details & air-tightness tester be 'spotting' these things?:o

thanks bryanf, I hope they will but just finished them few today and wanted to get opinions in.

Curious Geroge

esox28 wrote: »

George hey, don't get me wrong im not criticizing the taping but if your serious about airtightness your approch won't give a good result as it stands.
You ask wheather skim will go straight on to the reviels...well I wouldent for two reasons,first is the skim will crack at the window intersection with the tape, using bonding first may over come this if built out before skimming, secondly you have about 15mm taped to the window frame which will be seen if only using skim at a depth of 4-5mm.

What I think you need to do is start again.

as you have a block reviel right up to frame, I would get the reviels plastered with a smooth finish sand/cement then tape frame to plastered reviel.

When window are all taped up then plaster in the edge of the tape to the plaster with some bonding, just for extra protection.

Fit your 12.5mm plaster board for reviels and leave a protruding edge of 10mm for the plasterer to meet with sand and cement gray coat from wall.

thanks esox28; I had thought seal the window frame to blockwork as done, then plasterboard around the window reveal with protruding mm to allow for finished plaster and then finish plaster the plasterboard.

Should I sand and cement the window reveal before applying plasterboard ? And is applying the plasterboard best done with a tuple or bonding ?

Very little info on best practice when doing blockwork that I can find.

BryanF

Best to Skim coat all the blockwork first

Curious Geroge

BryanF wrote: »

Best to Skim coat all the blockwork first

By skim coat do you mean sand and cement prior to finished wall ?

BryanF

Curious Geroge wrote: »

By skim coat do you mean sand and cement prior to finished wall ?

yes

Curious Geroge

BryanF wrote: »

yes

Cool, that's a couple of weeks out as the weather is allowing us to kick off outside plastering. The plan was to sand and cement, put the plasterboard around the window reviel, attach using tuples and then finish plaster. Your recommendation is to sand and cement and then tape and then apply plasterboard if I'm right. I can see why as the sand and cement seal the pours in the block before the seal is applied. How far wrong have I gone ? I seem to be getting different advice from one stop to the next but I've found good value in the forum. Is there any detailed resource's on how to for blockwork ?

Curious Geroge

Coming back to this post for any advise. With waste pipes that go outside of the house – if plastered around, do you still need to apply a membrane ? Also, at ground level, around the perimeter of the house - before laying the insulation / screed or after?

Someone mentioned asking the airtightness tester but he's not due on site for the 1st test until the sand and cement is done on the outter walls first..