Damp smell in the living room

kelbal

Hi. We live in a semi-D, about 40 years old. For the last year or so there's been an awful damp smell in the living room. You don't notice it too much if there's doors/windows open, but if the room is closed up for any time at all, it really whacks you when entering.
There's no obvious mould on the walls. The windows are double glazed. I have one regular radiator and the natural fire has a built in back-boiler. I tied up the ball-cock on the heating system overflow(expansion) tank in the attic to see if there's a drop in the level, possibly indicating a leak. The tank is small enough, about 50x20cm. Over a 2 week period it seems to have dropped about 5mm roughly. I'm not sure if that's indicitave of a leak, or would that naturally evaporate anyway.
The floor is solid walnut, what was laid on top of the chipboard floor which was already there, which itself sits on the joists. There's a subfloor/crawlspace of about 1.5/2 feet.
We're at a loss as to how to investigate this. I'm so reluctant to pull up the wood flooring, to crawl under and examine with a torch, but without doing this I'm not sure how to figure out what's going on.
There's no obvious damage to the brickwork indicating rainwater getting in.
Would really appreciate any ideas.
Thanks

MicktheMan

Has there been any interference with the sub floor ventilation?
Do the people in the other half of the semi-d notice anything or do they have a leak?
Have you made any changes in the house which corresponds with the arrival of the damp smell.

Fingers Mcginty

5mm over a fortnight is ok I'd say. I did the same in out last house and the overflow tank almost emptied overnight.

dpofloinn

Whats your ventilation situation like in this room? Is the room closed up a lot? Do you regularly wash the floors with a wet mop? Whats the chimney set up for your fire place ie: does rain come down your chimney during bad weather? has your chimney been cleaned recently

kelbal

ventilation - there's a subfloor vent externally at the front of house (where the living room is), which seems intact, not blocked or anything. There's a conservatory added onto the entire back of the house, and the conservatory has a similar vent - but I'm not sure if there was an old vent on the back of the main house which might have been covered over when the conservatory went up. The conservatory is there 10 years, smell only occurring the last few months On the main house, the vent at the front is the only visible one.

Chimney - cleaned it about 2 or 3 years ago, and there was barely anything. My fires are always wood based, I buy about one bag of coal a year, so the chimney is staying pretty clean. I cleaned out old ashes the other day which had been sitting in the fireplace for months, and they were dry and unclumped, so don't see any evidence of rainwater coming down chimney.

The room is only closed up the odd weekend we're away, nothing excessive. I do wash the floor with a mop, but not regularly at all, and I make sure to wipe it up so that there's no heavy water left on it, its air dry very soon.

Neighbour doesn't think she's noticed any smell in her house.

kelbal

A possibility that occurred to me is that maybe there's a leak in the mains water supply to the house, which comes from the front, passes under the house, to the kitchen at the back. However I don't have a water meter installed yet so can't measure if there's any loss.

vrrv

5mm drop is minor in my opinion I would be inclined to agree with you that there could be a leak on the mains coming into the house! Will be very tricky to find it!!