ICF and Insulated Raft Junction

[PaddyP]

Hi all,

 

I am currently building a house using a Kore insulated raft foundation and 350mm Amvic Passicve ICF block. Since the ICF walls have been completed we have noticed patches of damp on the slab where the ICF wall meets the floor. These damp patches are located randomly around the perimeter and are not located just under windows so doesn't appear to be an issue with sills. The raft foundation is our finished floor and will be polished in the coming weeks.

 

After contacting Kore their solution to solve this problem and prevent further issues is to install a basecoat and seal the connection this way. However, the house will battened and clad in corrugated metal so this solution is not of much use to me. From what I unfortunately only now see, this seems to be a fairly common issue. We have not yet completed our external cladding and flashings yet so perhaps that will solve the problem by directing water away from the junction and I am worrying prematurely. However, if this does not fix the problem it will be much more difficult to fix after cladding so would like to go overkill now if necessary.

 

Detail below was used during construction. Stepped DPC detailed was not installed due to the starter bars. In hindsight a hydrophilic tape/waterstop should have been added but unfortunately too late for that now.  

 

Has anyone come across a product solution to this issue?

 

 

 

 or can think of a

 

 

[FM2015]

Is your roof and guttering on?

[Russell griffiths]

Triton TT waterproofing membrane. 

Two coats painted on, from below ground to about a metre up. 

Just batten over it. 

Or use one of the peel and stick membranes, below ground to 300-400mm up. 

Stick the cement board directly on to either solution, and just batten down over the cement board. 

[saveasteading]

Assuming your overclad comes nearly to ground, then rain will drop off and run away, and only the very bottom of the cement board can get wet.

I think I would paint the bottom (exposed area plus 100 above and all the way down) in black bitumen paint, 2 coats. this then looks like  a narrow shadow in finished form.  (Blackjack or eq, £25/5l tin.)

[PaddyP]

Thank you all very much for the replies. 

 

Yes @FM2015all roofing and guttering is on and windows in. Just awaiting external cladding and flashing to arrive and install.

 

Thanks @Russell griffithswill have a look into the triton and see if any local builder providers have a stick on membrane available.

 

Sounds good @saveasteadingcheap and cheerful! Is it blackjack suitable for painting directly on to eps? 

[PaddyP]

Would this maybe do the trick as an extra layer of protection ? 

 

https://www.screwfix.com/p/bostik-flashband-grey-10m-x-150mm/55009

 

 

[saveasteading]

4 hours ago, PaddyP said:

Is it blackjack suitable for painting directly on to eps

I think it will melt the eps! I only meant to paint the cement board.

I have done this for years on exposed block footings below cladding (so only 2 blocks high and hidden apart from 150mm or so. It is effectively unnoticeable and all water is repelled.

[Russell griffiths]

14 hours ago, saveasteading said:

Assuming your overclad comes nearly to ground, then rain will drop off and run away, and only the very bottom of the cement board can get wet.

I think I would paint the bottom (exposed area plus 100 above and all the way down) in black bitumen paint, 2 coats. this then looks like  a narrow shadow in finished form.  (Blackjack or eq, £25/5l tin.)

You cannot use any bitumen based product on eps or  xps, it will just dissolve it. 

Must be waterbased. 

[Russell griffiths]

@PaddyP buy the correct product. 

Triton will be order in you won’t find many stockists. £175 for a big bucket. 

Buy the peel and stick from your icf supplier. 

Or buy peel n stick from a waterproofing company, must be compatible with eps. 

Dont use any bituminous based product. 

[PaddyP]

Thanks @Russell griffiths will have a look for a Triton stockist  in Ireland as that's where I am based. I cannot find any peel and stick membranes online. Could you direct me to any brands? Will also contact ICF supplier. Thanks a million.

[Russell griffiths]

Nudura do their own one, do you have a supplier over there. 

 

[Conor]

2 hours ago, PaddyP said:

Thanks @Russell griffiths will have a look for a Triton stockist  in Ireland as that's where I am based. I cannot find any peel and stick membranes online. Could you direct me to any brands? Will also contact ICF supplier. Thanks a million.

Try sdg in Armagh, they supplied the tanking system for ICF basement. Speak to Darragh. They do a paint on liquid suitable for ICF.

 

At our ground floor level we fitted additional external insualtion. To prevent the tanking being bridged, the lapped over another wide layer of dpc over the tanking, up 200mm and back through the ewi to the render bead above ffl. I used the paint stuff around door thresholds.

Edited February 8, 2022 by Conor

[Budgie]

3 hours ago, PaddyP said:

Thanks @Russell griffiths will have a look for a Triton stockist  in Ireland as that's where I am based. I cannot find any peel and stick membranes online. Could you direct me to any brands? Will also contact ICF supplier. Thanks a million.

Contact Barry Fingleton at Warmbuild via http://warmbuild.ie/ he will be able to supply the Nudura peel and stick membrane.

[saveasteading]

Have I misunderstood? I thought the cement board was all that was exposed after cladding.