Cavity external doorways- returning blocks inside to out?

[daunker]

I'm doing a conversion with existing blockwork. There are two openings for doorways, one ive cut and the other was always open. Internally there is a course of 140mm block that I am laying fresh and then will be dpc and timberframe sit upon this.

 

Outside to in will be render, 140mm block, 25mm ventilated cavity, 50mm PIR, 11mm osb then 145mm timber frame 11mm osb inside and plasterboard. Rockwool between studs.

 

My question is, friend has said on the other opening (no existing external course of blocks) I should return blockwork from inside to out, and on this one I should have returned it. As I haven't I should infill (with concrete).

 

Is this right? Is there another way. I kind of presumed I would just get those cavity closers, I am mainly concerned about cold bridging, but also want to do it right!

 

I'll be running the celotex on outside of timberframe 'long' so that it overlaps the top half of the block, to give some insulation and inside I have insulation and then screed with ufh so again will have a strip of pir around perimeter.

 

 

I was wondering if I should get some marmox thermoblock just for these openings. I could afford to do a course around the whole building hence using the blocks I have.

 

Fingers crossed someone knows and thanks!

 

Edited February 14 by daunker

[daunker]

Ok so heres a photo. Single course of 140mm blocks timberframe to sit on top. Finished floor level is a little below block height, will be a 25mm celotex upstand internally and 150mm insulation then 50mm liquid screed with ufh pipes in it.

 

Timber frame is 145mm with rockwool between studs then going out 11mm osb, breather membrane, 50mm PIR then 25mm ventilated cavity. I was going to also run a say 10m strip of 50mm PIR externally on inner course of blocks. 

 

Is returning blocks like this a normal design, feels a little cold Bridge-y?

[Faz]

No - that's the way to do it to stop the screed pouring into the cavity. You won't have a cold bridge issue.

[Iceverge]

I'm a fan of insulation external to timberframe but I'm not sure how you'll fit it? 

 

What's the door going to be sitting on? 

 

Sketches would help. 

[daunker]

That's good to hear @Iceverge . Most fit the pir to the inside and it did make me worry a bit. All of a sudden the breather membrane isn't going to do much breathing with celotex fixed and taped to outside, but I liked not having it internally.

 

So the timberframe soleplate is going to sit on the block and I've preconstructed it, because having to build back to front. Made panels bit big really should have done smaller for the lift. But be good when they're up. See photo.

 

@Faz that's encouraging but the inner course of blocks is going to run whole way around I think? I just left those blocks off as wasn't sure what to do. I was thinking of maybe getting a couple of marmox to sit in the opening and for the door to be sat on. I think the door requires solid underneath. Was wondering about concrete. There will be 25mm PIR upstand internally to the blockwork for screedng up to. 

 

Around window openings I am just going to have timber closing cavity. Ive used the plastic ones with foam before, but I'm really not convinced in real world situation they are very good, very hard to seal. Will be dpc on the face of it and then screwed to frame. This is because velfac windows sit on finished render. I was probably thinking the same of the door opening. Windows will be on straps so back overlaps with the insulation and front is sealed against (but not fixed to) the block. Was kind of thinking doing same with the door? 

 

Nb a lot more fixings for pir now. I used a mix of zinc washers and plastic ones I had left over mostly used the plastic ones for joins as they are quite oversized. Wasn't really sure which was best so hopefully a mix will work. 2.4m high and 400m stud spacing 3/4 per stud

Edited March 2 by daunker

[Iceverge]

4 minutes ago, daunker said:

. I think the door requires solid underneath

 

It certainly does, 

 

How wide is your door frame?

 

If its say 80mm you could easily have the door supported on 40mm of concrete externally and floating over 40mm of PIR internally. So long as there was a continuous line of insulation this would work fine.  

[daunker]

852x2200mm 'element weight" 89kg

 

Internally will be 150mm PIR then 50mm liquid screed with ufh pipes. So that's the sort of makeup I have hence the course of blocks height, although it's slightly above my ffl. What do you reckon would be best? Door has 25mm threshold so fairly flush with finished floor.

 

Was planning to put a strip of 50mm PIR on the outer face of the course of blocks maybe 10cm high and fix in mortar join as well thought that would help and overlap with the height of internal screed. Ok it wouldnt be taped to the pir on timberframe but it would hopefully help as an additional thermal break to the 25mm upstand internally.  Sorry I'm getting sidetracked here. Really appreciate getting feedback from my own project where I just deal with my own voice in head. Thank you. Really value any input

Edited March 2 by daunker