Resin Patio blocking air brick

rajanm

We're currently having our patio redone in resin.  As part of the work, we're raising the level of the patio.  It's going to come up just under 3 out of our 4 air bricks at the back of our house.  For the fourth one it's going to cover half of the air brick with the other half of it being exposed.  

My builder thinks it should be ok as resin is permeable but I'm a bit concerned.  The only other option is to have the patio slope by about 3cm where the fourth airbrick is.

Does anyone have any experience of this issue and any thoughts on the best course of action?

Apodemus

rajanm said:

My builder thinks it should be ok as resin is permeable but I'm a bit concerned.  

Ah, the Great British builder...!  The resin may be permeable (although I suspect even that is marginal) but I wouldn't want to try and breathe  through it...which is what your house wants to do with your airbricks! 

FreeBear

So where does the surface finish in relation to your DPC ?

It should be a minimum of 150mm below the DPC. If your air bricks sit on top of the DPC, then you are going to be way too high and run the risk of penetrating damp.

rajanm

FreeBear said:

So where does the surface finish in relation to your DPC ?

It should be a minimum of 150mm below the DPC. If your air bricks sit on top of the DPC, then you are going to be way too high and run the risk of penetrating damp.

I measured the proposed level of the new surface an it looks like it will be about 9-10cm below the DPC.  The air bricks are all below the DPC

grumbler

rajanm said:

FreeBear said:

So where does the surface finish in relation to your DPC ?

It should be a minimum of 150mm below the DPC. If your air bricks sit on top of the DPC, then you are going to be way too high and run the risk of penetrating damp.

  The air bricks are all below the DPC

IMO that's very odd.

Edit: I misread this as "well below". Yes, typically the membrane is on the top of airbricks.

Regardless, it's a bad idea to have patio covering partly an air brick. I'd leave at least 10cm gap between the patio and the wall or make sort of a box around the air bricks.

And slope, if any, has to be in the opposite direction, not towards the house.

FreeBear

grumbler said:  it's a bad idea to have patio covering partly an air brick. I'd leave at least 10cm gap between the patio and the wall or make sort of a box around the air bricks.

A finished level 90-100mm below the DPC is less than ideal - I'd go for a shallow trench about 200mm wide and fill it with a decorative gravel so that the air brick is fully exposed. It will also reduce the amount of splash back when it rains and hopefully avoid any issues with penetrating damp.