Beams on inner leaf of trench blocks instead of inner leaf of cavity

[Tony L]

Does this look OK?  I don't understand how it's going to work.

[Tony L]

What's built doesn't match the drawings the builder is working from (which I did understand).  See below

[Tony L]

& what’s been built doesn’t match any of the diagrams I see on the internet, which mostly have a gap beneath the insulation to help any water in the cavity drop down onto a slope that directs it to the outer leaf.

 

The drawings the builder is working from show beams sitting on DPC on the inner leaf of a cavity wall.  I can see this makes sense, because any water inside the cavity wall will drop down beyond the beams.  With the arrangement that’s been built, any water in the cavity could pool right next to the beam & as soon as it’s 2mm deep it will be over the top of the DPM & onto the beam.

 

He told me he was going to put a tray in, but it seems to me this tray will not be in the best possible position.  & if there’s a tray sloping to the outside wall, doesn’t that mean there will be no insulation against the B&B floor?

 

Air bricks: All the diagrams I see have the inner vent of the periscope lower than the beams – it doesn’t look like that’s what my builder is planning to do.

 

The outer skin of the house will be rendered blocks.  The builder knows we want standard size black bricks, beneath the render, going into the ground.  Presumably, he’s intending to lay 2+ courses of black bricks on top of the edge of the trench blocks then build up the ground so we can’t see where the black bricks meet the blocks beneath ground level.  I think there will be damp coming through from the ground & into the trench blocks the beams are sitting on.  Does this matter? 

 

This (below) is much closer to what I was expecting:

 

[nod]

Looks fine 

[Russell griffiths]

I think because your build method has changed you need to stop work for a couple of days and get a few drawings done, they only need to be sketches, but it will give the builder the chance to explain what he proposes, it will give you chance to come on here and show us, and it will give you chance to understand how it will all tie together. 
 

those two pictures you put up. 
the second one with the green damp proof membrane is exactly what you have. 
he’s not put the dolly blocks in the gaps below the blocks to cap the ends off yet and the end row of blocks are not in, but that’s pretty much what you have. 
your trench blocks will be underground and will always be wet, that’s pretty standard. 

Edited 16 hours ago by Russell griffiths

[Russell griffiths]

Where’s the drainage???

[Oz07]

Ive had them sit like this before. I used a wider dpc though, then folded it up the ends of the blocks and taped it to the dpc ontop of b&b. Then I had a small bit of concrete in the cavity directing water outwards. Im not sure how effective the concrete is, i wanted it more to stop the ground pushing the external leaf inwards. 

 

I dont think drainage for water underneath the floor is a standard detail. Maybe only on waterlogged or high water table sites. You don't see it on any of the big sites round here. Obviously you need drains for internal stacks but this could have them coming out external walls?