Ventilating a suspended timber floor where airbricks have been covered up

[Mikewall95]

First time poster and rather new to DIYing so please go easy on me.

I noticed that when lifting up floorboards on my new 1930s property, that there were some large damp patches on the concrete foundation towards the rear of the property. On closer investigation I found that whomever had constructed the rear extension did not deem the existing airbricks neccessary, and so covered up with concrete and didn't allow for any other route for ventilation.

The only feasible solution I can see would be to cut a channel in the concrete slab, install a vent leading to the outside and concrete back over.

I appreciate I will probably have to throw some numbers at this to work out what free area of venting I require for the area of floor I have, and I may need more than one channel, but if someone who has more understanding on ventilation than I could give me a nod that what I propose to do isn't out the ordinary, that would be much appreciated!

 

[turpis]

I think you're jumping to the conclusion that the damp is a result of poor ventilation. How old is the extension? Many old concrete slabs (and probably a fair few modern ones) have an improperly installed DPC.

Prior to lifting floorboards were there any visible issues? If not, there is always the option of leaving it as you found it, maybe clearing out any debris under the suspended floor to encourage air flow.