Adding damp proof course to French doors

ashe

For reference this is what we had in prior to today, the sill covered the internal DPC strip and cavity and prior to this, it was just a standard window with a wall underneath it. 

ashe

Ok, doors all done and much nicer looking than old window and much higher quality than the French doors in our kitchen. 

With ref to the cavity @stuart45, it looks like on the internal floor side it's all concrete up to the lip, which has a layer of dpc across it and then and then this blue layer which hangs down to the bottom side 

This goes down to the bottom of the gap 

So don't really have any brick to remove and I don't have anything for breaking concrete. Is this a necessary step? Or can I just dpc layer the external brick wall and bottom of the cavity and fill?  

ashe

Also as it links to the house cavity there is a fair draft, is there anything I need to do to draft proof it? Guessing foam would bridge the gap for damp?

stuart45

Under the DPC should be brickwork. The blue is the DPM.

FreeBear

Go on, post some images of how things are progressing. I'm sure others will be interested

ashe

So thanks to freebear's generous offer of an off cut of dpm, I set about getting two bags of concrete thinking I could take one back. It didn't quite work out that way 😂

I also bought some thermalite breeze blocks to cut up and fill in some of the support area to save in using a lot more concrete - if I hadn't done that I prob sky would have used a lot more concrete!

the dpm arrived Monday and yesterday I set about sawing up the breeze blocks with a chewp
saw i had bought, with a view to only having to fill the sides and the top 10cm or so 

Quite pleased with how they came out done by eye, and then measured them out along the gap to make sure I had enough for the width then used a batten to push the chunks of brick and crap that were in the cavity out of the way and put two chunks of breeze block at the sides to hold the concrete in place 

I set about mixing the concrete which was a graft, put a layer in the cavity at the bottom to give a roughly level surface and then put my DPM in the cavity and folded the corners over then put another layer of concrete at the bottom of the dpm then inserted my breeze blocks 

It was slow going and I rapidly realised I would need the other bag so got as much of it in as possible whilst keeping on mixing it so as it didn't set in my bucket, then quickly mixed the other bag up. I made sure to push it in around the breeze blocks, pushed it into the sides under the wall and smoothed it out on top 





my concrete in the middle looks great but at the sides it looks a bit pebbly. I'll give it another day or so to dry and then freebear has suggested some self levelling compound on the top so I'll report back once I've completed those steps!

Few questions;

There is a small gap where it looks like due to the narrow gap between the door and dpm the weight of the concrete hasn't fully pushed it against the wall, but it is minor. Is it worth putting some cement in that to close the gap or would it just crack anyway?  It's a little bigger than in the pic below because there is a layer of dpm on the internal side too, it's about 5-8mm wide but only at the top , lower down it fills out. It won't be stepped on I shouldn't think 

Should I trim the dpm to floor level, or should I fold it over the filled concrete so that it's covered?

at the sides there is still the cavity where the sill was and skirting is going to go around that - I can feel some draft from this - is there anything I should be doing to block the drafts without causing damp issues? Expanding foam? Or just block it with skirting and caulk ? Should I be trying to wedge something under it so that that small part of the wall isn't unsupported? 

FreeBear

A squirt of expanding foam in to the gap either side of the door reveal will stop the draughts. You just need enough to plug the gap, so no need to go emptying a whole can in there.

ashe

FreeBear said:

A squirt of expanding foam in to the gap either side of the door reveal will stop the draughts. You just need enough to plug the gap, so no need to go emptying a whole can in there.

Cheers freebear I'll get on that today. 

So I think you said to snip the dpc down to floor level once it has set, then just a case of adding some self levelling compound on top to smooth out the surface?

do I need to add anything into the gap to shore it up? Would the levelling compound help there or would it be too weak?

FreeBear

If you plug the gap(s) with expanding foam, it will stop the self leveling compound from oozing out.

ashe

Quick update - carpet down today. 

I plugged the gap with expanding foam and poured screed. This worked really well, initially. However there must have been a small route either side that the screed could squeeze through so ended up with some gaps at each edge where the two don's butted up

Frustrating! I let it semi set and added some more and built it up in some layers but didn't get a photo of it. Not wanting to fill my cavity with screed I left it there, and let it set and just filled the gap with some mortar to give it a level surface, this hardened nicely and left it a few weeks to cure and today we've had the carpet put down

Probably Quite  an unorthodox way to get to the end solution, but as the gap was so narrow it was hard to fiddle with the dpm to get it perfect when it was folded in, and it's where that dpm fold was and the existing blue plastic sheet was that had the gaps.