Musty damp smell but no damp

dramaticat

The house I am interested in buying is a split-level bungalow built on a hillside. Most of the bungalow is at the upper level, but there is a lower level that is a semi-basement that extends back right under the rest of the house. There is a musty damp smell on the stairs down to this room. The smell is very localised just to the staircase – there is no smell in the semi-basement room once you move away from the staircase, nor in the area that extends back under the rest of the house. There is no obvious damp area on the wall by the staircase.

I had a damp survey done by an independent damp surveyor, who confirmed there is no damp in the property, but more unhelpfully said there was no smell either! I noticed the smell slightly when I first viewed in the summer after a long spell of dry weather. I went back a few weeks ago after we'd had a lot of rain and the smell was very much stronger. Both my friend and a builder who came with me immediately commented on it without prompting – the builder saying it smelled damp. Even the estate agent commented on it later.

Can anyone suggest what might be causing this smell? I'm not scared of sorting out damp if I know what's causing it, but not knowing what the problem is worries me.

FreeBear

At a guess, I'd say the walls in that area are relatively cold and subject to a degree of condensation. Couple that with poor air circulation, and a musty/damp smell is to be expected. Getting some heat in to the space along with some air flow will help to alleviate the odour.