Block & Beam waterproofing

[EdSt]

Can I ask how have others have achieved waterproofed block and beam (B&B) layouts? ..

 

I’m doing a B&B patio to extend out from new single floor kitchen/dinner extension. Level of garden is approx 1.3 meters to top of foundation cover, so plan to use the undercroft below for storage of scaffold, mixer, wheely bins, kids plastic garden toys/tatt I.e generally inert outdoors stuff - so no Rembrants - but maybe some seasoning/seasoned logs/firewood.
 

The patio span is 5M (by x7M wide) and I’m thinking of breaking down into 3M&2M with support wall, to remove any bounce. (Bounce question will probably be another forum post!)
 

Current thinking on patio surfacing is 37mm 600x600 pavers set on wall barn pedestals and lay these on top of some kind of membrane (Edpm?). Looking to achieve 60mm total thickness by extension to sit level with 50mm Aco sat on 10mm bed to pick up the drainage on the bifold cill - aiming to achieve low threshold (again subject if another post most likely).

 

I’ve read about people tanking B&B with cementious products but not really feeling like that would be robust given potential for cracking with heat expansion and bounce, all-be it greatly reduced. Concerns with edpm would be cost and also risk of puncture once loaded from concrete snot/grit from the beams or block concrete products.
 

With project to date I’ve found the build hub forum supper helpful so hopeful for ideas and input on this one. Thanks in advance!

Ed

Edited September 1, 2024 by EdSt
Minor amend

[Conor]

Our balcony was originally meant to be block and beam but the waterproofing detailing was far too complicated. B&B, screed, insulation, OSB, membrane, then paving. In the end I got the engineer to redesign in timber /steel and I simply did a fibreglass covering before paving on pedastals. Final build was 150x50mm C24 joists at 400mm CC (set in steel frame), 18mm OSB, then coverings. There's a bit of bounce from the 6m wide main steel, but just there to remind you you're not on the ground.

 

 

[EdSt]

Thanks Connor. Committed to b&b now.

[Russell griffiths]

Look into a company called triton, they do all liquid type membranes, painted on and then screed over the top. 
 

the weak areas will be your details at junctions. 

[EdSt]

Thanks Russell 👍