More air bricks or full the subfloor with concrete?

[Plo]

Hi, new to this site and looking for some advice! Just had a substantial extension put on our 1930s detached house - it's double storey and wraps around the side and back. However we've just discovered that our builder did not duct through the ventilation on the side of the house or at the back!!! We still have air bricks at the front and on the other side but have obviously now lost our cross ventilation.

My other half has been into the subfloor as we've been insulating between the joists (which is how he realised we've lost our cross ventilation) - we're planning to install ufh in the next few weeks hence insulating. The air under our hallway feels quite stuffy but it's not so bad on the other 2 rooms... building control suggested adding in a couple of air bricks under the front door (there's no ventilation in the hallways currently) and my husband is adding in another air brick at the side of the house.

My question is, do you think that's enough? I've been thinking about the option of filling in the subfloor space with concrete - anyone got experience of this? Thought we might just do the hallway as that is the area of most concern and add in air bricks at the side of the house for the other rooms.

The subfloor space is about 30cm under the hallway up to the floor board level (it's about 20cm under the joists).

 

[tomfe]

Are you going to take up all the floor boards to insulate?

 

[Plo]

Are you going to take up all the floor boards to insulate?

No, my husband has been going under the floor to do this (it's been a proper squeeze in places!)

 

[JohnD]

cutting additional ventilation is a much smaller job than tipping in hundreds of tons of concrete.


And tipping in concrete will not, of itself, prevent damp.

An airbrick every two metres is not too much.

 

[John D v2.0]

get a moisture meter and check how damp the wood is under the floor already. if it's all ok, as above add as many air bricks as you can be bothered to now, that'll be good insurance against later. If it's not OK, consider resolving the dampness problems first, and again add plenty of air bricks.