Foundation Problems

[Jadele]

Hi Guys

So I have a problem. I got a guy to build my foundations for a new conservatory I want to build. Long story short is I think its now a real problem to continue with what I have. The block have been laid on their belly making each course 100mm deep and 215 wide. This has been brought all the way up too DPC level of the house.

As I see it now this leaves me without a cavity below DPC on the dwarf walls. When I asked about it he said for the sake of size of the wall I may as well have solid walls with no cavity and that's why he laid them lengthways leaving me with no room to space the block for a cavity.

Now I don't want to discuss the rights and wrongs of his advice or how it should be done etc because I am passed that point now. What I need to know really is, is is possible to make good on this base. I was thinking that I could pour my slab within the foundation he made and build a second wall straddling the upstand insulation? as shown roughly in the drawing attached to the right - the dark blue being house DPC and the light blue conny dpc. The main picture is roughly what I have at the moment to work with. Any help much appreciated.

 

[John D v2.0]

You can't build a wall on your upstand! can you drill some screws into the existing blocks he's laid to tie together and lay another stack next to it? Then you can build on top of that.

 

[freddiemercurystwin]

Yes just build another single skin of blockwork off the foundation on the inside to give you a wider wall to start with.

 

[Jadele]

Hi John. Thanks for the reply. I was thinking like max 25mm wide upstand then the internal thermalite skin would sit about 37mm on the block work 25mm of insulation and 37mm on the slab with the insulation underneath in the middle.

Not sure what you mean about screws. I have attached a pic so it's more obvious what I am dealing with. Thanks.

 

[Jadele]

Sorry forgot pic. Thanks Freddie but I forgot to say I really want to avoid building another skin up due to the trench filling with water all the time.

 

[John D v2.0]

The screws are just to tie it together, as you won't have steel wall ties. Probably not important for a short stack.

 

[geraldthehamster]

Is it insulation you're worried about? You could build a single skin dwarf wall with blocks upright, and fix timber studwork on the inside with Celotex between/over.

 

[^woody^]

Build it in 9" and then line and insulate the internal face with the thickness equal to whatever cavity you were going to have.

Or, instead of dropping a skin in the trench as per FMT, if you are concernd about the water then just fill it with concrete and drop the skin in when it comes above ground level.

Your crap builder should be paying for it regardless.

But that still leaves that horrible stupid block face on the external, visible above ground level. WTF is that all about?