Most houses with timber floors that are on stumps have a similar bare earth under the floorboards, so they often smell a bit damp and musty. Most freestanding houses minimise this problem with air vents around the perimeter that are below the floor level and above the ground level to encourage cross-flow ventilation which helps keep it dryer. However in a mid-row terrace house you have less opportunity as you only have the front and rear for air vents.

I had a client with a similar problem who installed an exhaust fan under the house to extract damp air. It was permanently running and did the job. However years later when I was involved in a second stage renovation we discovered that the nearest downpipe to their dampest corner was not actually connected to the stormwater. So everytime it rained water pooled under the floor from the downpipe and the exhaust fan battled to dry it out.

I would suggest that you check and confirm that all of your old downpipes are properly connected with the stormwater before going to the expense of mechanical ventilation. Pouring a slab is an expensive way to try and fix the problem, and it won't fix it if you have a disconnected downpipe!

Best of luck,

Dr Retro

of Dr Retro House Calls

Hi Dr Retro, thank you, I've just checked - all of our down pipes go over the top of the house and go into the storm water right at the back of the property. However our water supply itself does go under the house, so we're going to do a meter check tonight to see if it moves while we're not using water. Thanks so much for your advice.

We had a damp problem with a house on sandstone foundations which act like sponges and suck up any ground water and cause rising damp. Our neighbors storm water wasn't connect so we had a river running under us. Fixing that, and having a new damp course installed where it had effected the walls did the job, good luck