A few DPC questions please

[ashdene]

Ive just finished laying my block and beam floor on my bungalow extension, ive sat all the beams on a DPC strip as requested by the manufacturer.

I now need to run 1 course of cut blocks ontop of the floor before I reach the bungalows existing DPC where I will put my new DPC strip for the extensions internal wall. Can these be cut thermolite blocks or will they need to be concrete blocks as they are below DPC

Also the polythene membrane that will sit on the block and beam floor prior to insulation and screed, Does this have to be lapped up and onto the wall DPC?
I hope not as I am not ready to start laying my oversite as I do not even have a roof yet.

Many Thanks in advance for any advice.

 

[noseall]

Blocks below dpc need to be 7n concrete fellas.

Dpm lapped onto dpc.

It is normal process and simpler to lay the concrete over-site whilst the building is open. It is possible to do it later but this involves fitting strips of dpm into the wall and hoping they do not get damaged. Not a good way at all in my book.

 

[ashdene]

Thanks for the response, im really hoping there is another way, I don;t see the point in laying the membrane and filling the oversite before I knock down the existing external walls as im just going to end up with an infill section to sort out between new floor and existing floor

ive seen lots of jobs where the whole building is finished and made water tight and then the membrane is laid down, lapped up the wall 6 inches, insulation and screed goes down and then polythene is just trimmed off flush

Surely thats the sensible way to do it for an extension

 

[theoldun]

Block and beam floor. Heres how we do them.
You have a dpc under beams. Assume you have three new external walls to extension. Do not bother to lay either course of block slips or commons to internal cavity walls to bring your dpc up level with existing. Lay 300mm wide dpc on top of block and beam with 200mm hanging over block and beam floor. thereby forming split level dpc between internal and external walls. Where this meets from new inner cavity wall and existing bungalow turn dpc 200mm up wall. Your external dpc will be same level as existing and chopped in to cover existing.
Complete extension up to finished plastering, including knock through. Lay your dpm, note dpm over block and beams and lapped over the 200mm of dpc that is hanging out. Where your dpm laps against existing bungalow wall, turn it 200mm up wall. Insulate and screed. Go up pub, get legless.
Anything you do not savvy then come back.
Regards oldun.

 

[ashdene]

Block and beam floor. Heres how we do them.
You have a dpc under beams. Assume you have three new external walls to extension. Do not bother to lay either course of block slips or commons to internal cavity walls to bring your dpc up level with existing. Lay 300mm wide dpc on top of block and beam with 200mm hanging over block and beam floor. thereby forming split level dpc between internal and external walls. Where this meets from new inner cavity wall and existing bungalow turn dpc 200mm up wall. Your external dpc will be same level as existing and chopped in to cover existing.
Complete extension up to finished plastering, including knock through. Lay your dpm, note dpm over block and beams and lapped over the 200mm of dpc that is hanging out. Where your dpm laps against existing bungalow wall, turn it 200mm up wall. Insulate and screed. Go up pub, get legless.
Anything you do not savvy then come back.
Regards oldun.

Thats great news thanks very much, So if I do it as you say, does that mean I can go straight ontop of DPC with thermolites? I will still need to trim a bit off the first course to line up with external brickwork height so my wall ties will lay flat, but thermo's are much easier to cut than concretes