Fitting advice

[JohnnyB]

I'm looking for advice on sealing around the windows and doors in our hempcrete house.

I was thinking I would use compriband tape and then airtight tape on the inside between window frame and studwork but the hempcrete doesn't have a smooth even finish and there are gaps under the timber spacers fixed to the timber frame.

Does compriband expand into small gaps and holes to seal tight againest the weather or would I be better to use FM330 foam and then us something else in the gap between the frame and wall to insulate the gap? 

If I used the foam any ideas on options to insulate the gap if it doesn't have compriband tape in there? Compriband would seem a little expensive/overkill if I use FM330 to seal the outside.

 

The outside is timber clad so I will have timber around the outside reveal and the inside will have woodwool board and then plastered.

 

Also any thoughts on fixing plates? I was thinking of simple metal strips but are there other options?

 

Thanks,

 

Johnny

 

[Nick Laslett]

@JohnnyB, I have some left over rolls of compriband, various expansion thickness if you want some to experiment with. TP651

https://www.illbruck.com/en-gb/products-systems/product-finder/tp651-trio/

 

 

[Redbeard]

Perhaps a v 'tight' coat of plaster (I would use lime, as I like it) for the Compriband to 'bear' on?

[JohnnyB]

4 hours ago, Nick Laslett said:

@JohnnyB, I have some left over rolls of compriband, various expansion thickness if you want some to experiment with. TP651

https://www.illbruck.com/en-gb/products-systems/product-finder/tp651-trio/

 

 

Thank you Nick, that is very kind.  cuold you send me your address please and I'll head round at some point very soon

[JohnnyB]

4 hours ago, Redbeard said:

Perhaps a v 'tight' coat of plaster (I would use lime, as I like it) for the Compriband to 'bear' on?

Yes, that would work but I'm not sure I have the time.  I would need to wait for the plasterer to come and put a thin coat on and then let it dry before I could fit the windows. The windows are arrive about the same time the plasterer is coming to start on the internal walls.   My previous attempts at plastering have been terrible so I'm not going to try doing it myself.

[ChrisInKent]

@JohnnyB I’m about to compriband tape my windows. Did you do the underside/ bottom of windows? All the videos I’ve seen just show top and sides taped.

[Mr Punter]

3 hours ago, ChrisInKent said:

@JohnnyB I’m about to compriband tape my windows. Did you do the underside/ bottom of windows? All the videos I’ve seen just show top and sides taped.

 

I do all round.

[Adaman]

Hi Jonny, you've probably already done the job, but I'd suggest burnt sand mastic to seal timber winders into a lime rendered masonry. It's hygroscopic and maleable throughout its life time to adapt to the expansion and contraction at differing rates of the materials around it.

  

https://cornishlime.co.uk/products/associated-products/cornerstone-burnt-sand-mastic/

 

or

 

https://www.lime.org.uk/burnt-sand-mastic.html

Edited November 24 by Adaman

[Adaman]

What width / thickness did you go for on those hempcrete walls?

[JohnnyB]

On 22/11/2024 at 12:21, ChrisInKent said:

@JohnnyB I’m about to compriband tape my windows. Did you do the underside/ bottom of windows? All the videos I’ve seen just show top and sides taped.

Sorry for the slow reply, I've been rather busy trying to get enough finished in the house to be able to move in and haven't been on here for a while.

I didn't use the compriband in the end as it needs a reasonably smooth/flat surface to work, and hempcrete isn't smooth. I ended up using the Illbruck FM330 expanding foam and that has worked well for my situation. I used it under the windows as well.

On 24/11/2024 at 19:25, Adaman said:

Hi Jonny, you've probably already done the job, but I'd suggest burnt sand mastic to seal timber winders into a lime rendered masonry. It's hygroscopic and maleable throughout its life time to adapt to the expansion and contraction at differing rates of the materials around it.

  

https://cornishlime.co.uk/products/associated-products/cornerstone-burnt-sand-mastic/

 

or

 

https://www.lime.org.uk/burnt-sand-mastic.html

I have done it but still have the main house to do next year so I will look at that for next time. As mentioned above I used airtight foam which has worked well but doesn't feel quite the right thing to be using with hempcrete but at this stage there have been a lot of compromises that's very few things I regret yet.

 

On 24/11/2024 at 19:25, Adaman said:

What width / thickness did you go for on those hempcrete walls?

It varies depending on the exterior finish and the wall build up needed to make the cladding longer up with the brickwork as we want it, but the thinnest sections are 380mm of hempcrete and 440 at the thickest.