Concrete slab edge

[richo106]

Hi all 

 

My 50mm screed (over insulation, ufh pipes and slab) has now been poured.

 

Round the external edges there is 25m PIR, 10mm foam and DPM sticking up around 100mm. With the internal walls just having the foam and DPM.

 

how do I finish this? I am having my external walls parged Friday so want to make it’s ready for them.

 

I am also about air tightness too as I’ve read on here about it could be a cause of leaks, so I’ve bought some airtight paint to seal all round the edge.

 

is it as simple as cutting it all flush and  then air tight painting it? Sealing it to the slab and blockwork before parging?

many thanks

 

[Nickfromwales]

Parge first, as nothing will stick to the pores of the raw block face. 
Then you brush apply something like Passive Purple (liquid airtightness membrane) and leave to dry. Then you can tape to that. 
You may just as well brush on the thicker (non-sprayable) stuff as your airtightness tbh, as you can push the brush down into the internal angle where the wall and floor meet, plus it’ll stick to most stuff too. 

[richo106]

19 minutes ago, Nickfromwales said:

Parge first, as nothing will stick to the pores of the raw block face. 
Then you brush apply something like Passive Purple (liquid airtightness membrane) and leave to dry. Then you can tape to that. 
You may just as well brush on the thicker (non-sprayable) stuff as your airtightness tbh, as you can push the brush down into the internal angle where the wall and floor meet, plus it’ll stick to most stuff too. 

Thank you, I am guessing I still need to cut everything level to the floor though yes?

[richo106]

49 minutes ago, Nickfromwales said:

Parge first, as nothing will stick to the pores of the raw block face. 
Then you brush apply something like Passive Purple (liquid airtightness membrane) and leave to dry. Then you can tape to that. 
You may just as well brush on the thicker (non-sprayable) stuff as your airtightness tbh, as you can push the brush down into the internal angle where the wall and floor meet, plus it’ll stick to most stuff too. 

Sorry just to confirm. I’ll trim everything down flush with the floor level then Parge coat and then air tight seal with tape and/or air tight paint (I’ve got aerosana visconn)

Many Thanks 

 

[Nickfromwales]

1 hour ago, richo106 said:

Sorry just to confirm. I’ll trim everything down flush with the floor level then Parge coat and then air tight seal with tape and/or air tight paint (I’ve got aerosana visconn)

Many Thanks 

 

Yup. How thick is the final wall covering? Parge then dot & dab a plasterboard on, or full wet coats to a paintable finish?

[richo106]

7 hours ago, Nickfromwales said:

Yup. How thick is the final wall covering? Parge then dot & dab a plasterboard on, or full wet coats to a paintable finish?

Yes parge then dot and dab so around 30mm a half the walls and then other half will be insulated PB or battens with PIR and PB

[richo106]

Hi again, after starting to trim back the edging it leaves me a few other questions if anyone could help with them:

 

how far do I ask the plasterers to parge down to on both the ground floor and first floor?

 

some of gaps range quite drastically, would it just be the case of some will need some wide airtight tape sealed to new slab and walls? 
 
all of my internal walls downstairs are made of block do all the internal walls need sealing to the new slab also?

[richo106]

Could anyone assist at all on the my questions above? Many Thanks

[crispy_wafer]

Parge as close to the floor junction as possible, squirty foam to fill any gaps around the screed edge to wall. then seal up the junction, I'm using paint rather than tape.  Internal walls I'd not bother parging, but the floor to wall junction would need dealing with as air leakage could still happen there.  It's a job I need to do too!  Ballache of a job in this heat too!

Edited June 15, 2023 by crispy_wafer

[richo106]

35 minutes ago, crispy_wafer said:

Parge as close to the floor junction as possible, squirty foam to fill any gaps around the screed edge to wall. then seal up the junction, I'm using paint rather than tape.  Internal walls I'd not bother parging, but the floor to wall junction would need dealing with as air leakage could still happen there.  It's a job I need to do too!  Ballache of a job in this heat too!

Thank you @crispy_wafer Good idea regarding the foam and then paint...that is the way I am going to go now as I have both on site currently

 

Yes I will not be parging internal walls but will seal the floor to wall junction as you mentioned

 

Much appreciated

[crispy_wafer]

@richo106 I had a quick play at this last night, depending on what gaps if any you have at the floor to wall junction, airtight paint may not be suitable on its own.  I used some Soudatight paint with their fibre based membrane as I managed to buy 6 rolls of it from Ebay last year, I lapped onto the floor and up the wall and covered with a liberal dollop of paint.  I can imagine airtight tape working just as well, depends on what materials you have to hand.

[richo106]

Thanks great thank you @crispy_wafer

 

I think I will just have to treat each different wall differently, I think it will be a mixture of everything to make it work

 

Thanks again