Does beam and block subfloor need ventilation?

[stavros.london]

Hi all,

My ground floor is of beam and block construction with a 150mm or so void underneath. I initially thought it had no airbricks whatsoever although I found out they had simply been covered / blocked by garden soil, patio slabs, etc.

I've read that the void needs to be ventilated and my engineer seemed to agree as well. However, I had an expert damp surveyor today telling me that it's only necessary on timber floors and is not needed on beam and block. So I'm confused: which is it after all?

Thanks

 

[theprinceofdarkness]

The person who designed the building thought venting was required. One hopes he knew what he was doing. It all depends on if water can get into the void. Being pessimistic, I would say yes, even if the design is for it to remain dry.
Frank

 

[noseall]

B&B floors require venting, yes.

 

[stuart45]

Apart from clearing any dampness in the void, it clears any gasses from rotting vegetation etc. Never seen a site where vents were not used on block and beam floors.

 

[stavros.london]

Thanks to all, that's what I thought but the damp "expert" guy confused me.

So now I have to find a way to keep them unblocked whilst I redesign the garden as I was looking to put bifolds that open up to a patio at the same level as the internal ground floor. Any ideas?

 

[John D v2.0]

Never mind the air bricks, where is your damp proof course. You could put a damp proof sheet from the dpc to 150mm above the patio, and put periscope vents on the air bricks. Or you could build decking instead of a patio.

 

[stavros.london]

DPC comes out at two brick rows above the airbricks, if that's any useful. Periscope airbricks sounds like quite a bit of disruption to me. What if I kept a 150mm "corridor" / perimeter around the house where I want to put the patio, for ventilation and drainage etc? With a grill cover or something.

I don't think I'm explaining it very well so I'll look for a photo.