Hi,

 

We had someone in to do the foundations for an extension i built three years ago, and they forgot to put any DPC down under the oversite, now i've swept and hoovered the base, i can see areas of soil which are damp (no idea how with how dry its been). I know older houses have this style oversite anyway, so would you do anything? And if so what?

 

Thanks for any input.

 

Regards

Mike

How can you see soil, isn't the oversite over the soil?

 

Older properties  (like sections of mine) with a suspended timber floor would ensure cross ventilation via air bricks to keep things dry. 

 

Also important if there are any dwarf walls supporting say floor joists mid span, that this has a dpc somewhere to protect any timber sitting on it from getting damp.

@MikeGrahamT21

Is your floor timber construction or concrete and does it have cross-ventilation of the under floor void zone?

19 hours ago, Onoff said:

How can you see soil, isn't the oversite over the soil?

 

Older properties  (like sections of mine) with a suspended timber floor would ensure cross ventilation via air bricks to keep things dry. 

 

Also important if there are any dwarf walls supporting say floor joists mid span, that this has a dpc somewhere to protect any timber sitting on it from getting damp.

 

Extension was built where we had paving flags before hand, and basically all you can see is the cement which was under the flags which is pretty decent, but has holes in places.

 

Yeah we've got plenty of air bricks and cross ventilation, including in the sleeper wall, which has DPC on top of it before the joists, so no damp will rise from there into the timbers.

 

I stuck a soil probe into the bits i could get to, and it actually registers as dry, so it perhaps is just dark soil which 'looks' damp.

 

Attached to this extension is a utility, and when they were building that, we had a huge downpour which filled the cavity between this extension and the utility, the concrete foundations are also higher on the utility, and I've a feeling its just the damp from that still percolating its way through which will evaporate in time.

 

Because there is no floor down at present in extension, the airflow is going to be massively hampered, as its just coming straight into the room, once the floor is airtight, the under floor ventilation will improve massively.

if there's already some mortar down, put down some DPM and concrete over the top to seal it.