Airtigtness of Wet plaster to screed junction

[FarmerN]

 

Screed has gone down today over UFH , next is wet plaster on block walls, how do I deal with airtightness of plaster to screed junction.

We have a 25mm perimeter upstand and an expansion strip between screed and block wall, so plenty of opportunity for air leaks down to the beam and block floor.

How should we deal with the wall floor junction?

Neither the builder nor plasterer are keen to plaster right to the screed, they both want the traditional gap behind the skirting board.

Builder of course says “ stop worrying , the DPM is well taped to the DMC , of course it will be airtight”.    I on the other hand have a major concern. We are having MVHR.

How should we deal with the wall floor junction?

Plaster to screed?

Airtight paint?

Blue foam in gap ?

????                       Thanks

[Andehh]

The screed will force the 25mm upstand hard against the wall, and with the DPM etc it never even occurred to me that air could escape through to block and beam.

 

Could run a thick bead of silicone along the interface between insulation and block??

 

Bigger fights more worth having elsewhere IMO, I don't see that air escape route being a thing in that location.

[nod]

Get your floor coverings down and skirting boards on

There's no real rush for a test 

[crispy_wafer]

Any gaps big enough to fit a nozzle into got the foam treatment... Then painted a load of airtight paint on as a primer, then taped over the lot.   Was an easy job, but it gave me an excuse to get away from real work!

[Russell griffiths]

I painted the gap and up the wall with 

Triton tt gas membrane paint

used it for all junctions, had an outstanding air test result. 

[FarmerN]

Thanks for replies.

My feeling is to do something at junction, either foam or paint or both.

I'm bothered if I follow nods advice and leave it until airtight test, after fitting skirting, it will be much harder to rectify any air leaks that I may find. I really don’t know how much the wall floor junction normally leaks air, especially with beam and block.

 

I keep wondering how much time it would take to make a rig with fan to depressurise the house, so I can go leak hunting with a smoke pen or whatever. I am guessing the professionals want to come, do test and go, without really looking for source of leaks.

[Russell griffiths]

I had an airtest done as the shell was finished

for £300 it answers a lot of questions and allowed me to get on without worrying 

[cwr]

Follow Russell Griffiths example and not mine. I should have done an air test at shell stage before boarding, and regretted not doing so. Got a few leaks sorted when we finnaly did the test, but there was still something going on behind a boarded service void that was by then no longer

accessible.

 

For screed to walls I tapped with pro clima content solido. Possibly  overkill, but we definitely didn't get any leaks there. 

[PNAmble]

1 hour ago, Russell griffiths said:

 

I had an airtest done as the shell was finished

 

+1.  Our first airtest is scheduled before the inner PIR, Cavity and Boarding is complete on our TF. It will be also before screeding. Aiming for less than 0.6 at final test.  £400 is loose change in context of the build and future bills.

[FarmerN]

 

13 hours ago, Russell griffiths said:

I had an airtest done as the shell was finished

for £300 it answers a lot of questions and allowed me to get on without worrying 

 

 

11 hours ago, PNAmble said:

+1.  Our first airtest is scheduled before the inner PIR, Cavity and Boarding is complete on our TF. It will be also before screeding. Aiming for less than 0.6 at final test.  £400 is loose change in context of the build and future bills.

 

How did you go about finding the leaks during these diagnostic air tests, and how long to allow?

We have a 215qsM bungalow under constucion, with large kitchen living space with vaulted ceilings.

[Russell griffiths]

The tester was on site for a couple of hours. 

You can get smoke sticks to detect air coming in. 

But it’s fairly obvious when you see the test being done. 

If the machine says it’s at 5 then you know you have a door or window open

down to 1 and you can start looking for small gaps, you can hear air whooshing in if you walk around silently. 

You want nobody else on site the day of the test. 

I found two holes in some caulking about the size of a knitting needle and I could physically feel the air coming in.