Subfloor Dampness: ventilation and vapor barriers.

Hello,

I have a 1920's semi in federation style on the northern beaches. We are getting strong smells of damp coming up through the floorboards.

I've attached two jpegs to help illustrate the problem.

The house is brick on a sandstone foundation (about 45cms in width!). The land slopes from the rear of the property to the front at about a 15 degree angle. We get sizeable runoff underneath the house from rain (and possibly a natural spring uphill from the property.) During heavy rains you can see channels in the dirt where the water flows under the house. The previous owners did a lot of work in the backyard to divert most of the flow though agpipes/drains to the side of the house, but there is still a considerable amount of moisture. The previous owner installed an fan in room "C" (attached jpeg) which seems to work pretty well for the back part of the house, but room's "A" and "B" do not have much airflow.

Getting cross ventilation is almost impossible due to it being a semi.

My thought would be to add two more fans, one for room "A" and one for room "B" along with an agpipe draining to the front of the house (See proposed.jpg).

Also, would laying plastic sheeting either directly on the ground or stapled to the joists help keep the moisture out of the house?

Also, if you think fans would help, any recommendations on a quiet one? I'm right up against my neighbours who are noise sensitive!

Any thought would be much appreciated! :-

Regards,
Dave.

i have a friend who sells these vents

his website
http://www.ridpest.com.au/fans.html