Level for Block Paving against DPC

[ac]

Advice is usually that patios etc should be two courses below the DPC assuming that the DPC is a thin layer between brick courses. However, the DPC in the outer skin of our bungalow is made up of two courses of engineering bricks. What level should a patio be in this case? Thanks.

[84-1093879891]

There's probably a polymer dpc on top of the two courses of Eng Bwk. Is there any other paving around the house? If so, check the level - it will probably be levelled with the bottom of these 2 courses, ie, 150mm below the dpc.

How old is the property?

[ac]

Hi Tony,

The house was built in the late 40's as far as I know. Because of the sloping plot, there are various bits of paving, concrete etc which are at various levels from 4 courses below the bottom of the eng bwk (foundation level) to level with the top of the eng bwk.
I cannot see any sign of any polymer DPC on top of the eng bwk but note that the polymer DPC in the inner side of the cavity is level with the bottom of the eng bwk in the outer side of the cavity. Inside the house the solid floors are damp proofed by a tar layer holding down the wooden floor blocks, which is level with the polymer DPC in the inner face of the cavity.
So a patio level with the bottom of the eng bwk would be at the same level as the floor indoors. Would this be too high, since our soil is heavy clay, prone to waterlogging in winter.

Thanks - Andy

[84-1093879891]

I had it in my mimd that this may be a more modern property, Andy, with a cunningly disguised dpc, but it's obviously not. :(

From what you tell me, I would work on a max paving level of 150mm below internal floor level, ie, 2 courses below the eng bwk. If you wanted to go lower] than that, it wouldn't be a problem, but most properties built since the mid 1930s rely on a minimum level diff of 6" (150mm) between internal floor level and external ground level.

How does that fit in with your plans?