Suspended groundfloor ventilation

[RichD1]

I've got a 1930's semi which has wooden floors and about a 4 to 5 foot crawl space under the joists. The bottom ground appears to be always damp as I believe that there are underground springs in our location. The clue is that the area is called ....... Spa.

The lounge floor and joists have been replaced back in the 70's and there are a couple of soft joists in the dining room which will get replaced soon.

The property suffers from quite a lot of condensation due to high humidity which I feel is coming from the underfloor void. We do implement all the anti-condensation tips, opening windows, extractor in bathroom, open kitchen window when cooking etc etc.

My question is; has anyone come across forced ventilation for the underfloor area?

Before someone asks, I have checked and cleaned out all the air bricks around the property.

Richard

 

[vinn]

Do you have through ventilation from front to back of the property?
Regs recommend a min. of air bricks every 1.5m to 2m.
245mm x 141mm (the old 9" x 6") plastic air bricks work best.

Dont attempt any "forced" elec or mechanical sub-area venting.

 

[RichD1]

Yes, air bricks front and back and to the side, all cleaned out. They are only single brick size though. Worth changing to doubles?

Richard

 

[vinn]

Possibly but first try seeing that from inside, from below the floor, you can see full daylight through them.
Any knee walls should be honeycombed for ventilation.
Lay full sheets of membrane (DPM) across the soil to act as vapour barriers - lap the DPM up the wall a few inches.

 

[John D v2.0]

Yes clean out your air bricks, remove paint etc, and if they're the clay type or cast iron like ours were then consider changing to the plastic ones as they're more effective.
We'd had a porch and a conservatory on our house before we bought, and I tried putting a blower through a hole in the floor. This determined that the air bricks in the porch and conservatory visible on the outside were just for decoration and weren't connected to anything under the floor.
That was about as close as we were to forced ventilation, really if you have free air flow then forced won't really add much unless you have a dead end or dead area to ventilate.

 

[RichD1]

Thanks for the responses.

Air bricks at the front have been replaced with plastic types. Probably when the lounge floor was replaced.

How effective would laying a DPM membrane on the overground?

Richard