Sealing VCL to concrete floor

[Andrew]

Our timber frame company are installing insulation and the vapour control / airtightness layer as part of their package. They have not sealed at floor level which I don't think will lead to very good airtightness as air will simply escape through this junction. 

 

I've attached a photo, construction is 140mm timber frame filled with fibreglass insulation, 50mm PIR over the studs and then VCL on top. At the wall / floor joist junction at the top I have convinced them to install a Terry tray detail which wraps around the joists and the VCL is taped to that. The floor is insulated B+B with 75mm concrete on top. There is a DPM but this has been lapped under the DPC underneath the sole plate. You can see the DPC sticking out under the wall. I'm tempted to tape to this but I guess there's still a possibility that air can escape underneath. Is the DPC normally trimmed and the VCL attached directly to the concrete floor? The floor is very dusty, I'm not sure the tape would stick very effectively if taped directly.

 

Thoughts / ideas welcome, thanks.

 

 

[Pete]

I had to prime the concrete floor, PVA or SBR and then used the appropriate tape for timber to concrete

[andyscotland]

Is the concrete floor your finished floor / do you need to bond to it (eg tiles)?

 

If not (e.g floating floor) then you could just lay a plastic VCL / DPM over the concrete and below the finished floor, bring that 100mm up the wall and tape it to the VCL. That would totally enclose that junction. May need to wait for the concrete to fully cure.

[ADLIan]

There is normally a vapour control/separating membrane between the insulation and the screed which then inks to the VCL in the wall. If not done then above both seem to be reasonable solutions though a full membrane over the floor may be a bit of overkill.

[Andrew]

Thanks for the replies. 

 

On 25/07/2020 at 09:50, Pete said:

I had to prime the concrete floor, PVA or SBR and then used the appropriate tape for timber to concrete

 

I think this is what I'll do. Do you happen to remember which tape you used? 

 

On 25/07/2020 at 10:27, andyscotland said:

Is the concrete floor your finished floor / do you need to bond to it (eg tiles)?

 

If not (e.g floating floor) then you could just lay a plastic VCL / DPM over the concrete and below the finished floor, bring that 100mm up the wall and tape it to the VCL. That would totally enclose that junction. May need to wait for the concrete to fully cure.

 

It is the finished floor, the intention is to have a glued down bamboo floor in some areas and tiles in others. Ignoring the fact I need to bond to it,  to get a completely airtight envelope using a VCL/DPM I'd need to cover the entire 140m2 ground floor which has lots of internal partitions / internal load bearing walls - sounds a bit of a nightmare tbh. 

 

On 25/07/2020 at 12:05, ADLIan said:

There is normally a vapour control/separating membrane between the insulation and the screed which then inks to the VCL in the wall. If not done then above both seem to be reasonable solutions though a full membrane over the floor may be a bit of overkill.

 

We used the Tetris insulated block and beam flooring system which doesn't need a DPM according to the manufacturer. Our SE specified a DPM anyway but this went under the top layer of Tetris insulation so we could staple the UFH to the top layer of  insulation before pouring 75mm reinforced concrete. That DPM was lapped under the DPC the timber frame sole plate sits on by the frame erectors. 

[andyscotland]

2 hours ago, Andrew said:

 

It is the finished floor, the intention is to have a glued down bamboo floor in some areas and tiles in others. Ignoring the fact I need to bond to it,  to get a completely airtight envelope using a VCL/DPM I'd need to cover the entire 140m2 ground floor which has lots of internal partitions / internal load bearing walls - sounds a bit of a nightmare tbh. 

 

Ah yeah in that case doesn't sound like a good plan.

[Pete]

5 hours ago, Andrew said:

Thanks for the replies. 

 

 

I think this is what I'll do. Do you happen to remember which tape you used? 

 

 

It is the finished floor, the intention is to have a glued down bamboo floor in some areas and tiles in others. Ignoring the fact I need to bond to it,  to get a completely airtight envelope using a VCL/DPM I'd need to cover the entire 140m2 ground floor which has lots of internal partitions / internal load bearing walls - sounds a bit of a nightmare tbh. 

 

 

We used the Tetris insulated block and beam flooring system which doesn't need a DPM according to the manufacturer. Our SE specified a DPM anyway but this went under the top layer of Tetris insulation so we could staple the UFH to the top layer of  insulation before pouring 75mm reinforced concrete. That DPM was lapped under the DPC the timber frame sole plate sits on by the frame erectors. 

I purchased all my tapes from Passivehousesystems but could not find the tape that I used. There is a black and green coloured tape that I used against the VCL but the colour of the tape that I used on the concrete floor/wall junction was a light green split 50/50 tape but it is not on their website now. May be others can recommend a tape for you, sorry.

[Andrew]

15 hours ago, Pete said:

I purchased all my tapes from Passivehousesystems but could not find the tape that I used. There is a black and green coloured tape that I used against the VCL but the colour of the tape that I used on the concrete floor/wall junction was a light green split 50/50 tape but it is not on their website now. May be others can recommend a tape for you, sorry.

 

Thanks and no problem. This tape looks pretty good for the job - https://passivehousesystems.co.uk/product/phs-5050-split-release-tape/

 

 

[Pete]

10 hours ago, Andrew said:

 

Thanks and no problem. This tape looks pretty good for the job - https://passivehousesystems.co.uk/product/phs-5050-split-release-tape/

 

 

That must be the replacement product, happy sticking. Make sure you fold the tape along its middle so you can stick one part before you do the other.