Gaps around new floor boards

[M R]

We had an extension about 18 months ago and the builder also redid the floor in the kitchen with fresh joists and boards.

I've noticed over the last few days in the cold weather that it is really cold, so I have dug out my IR camera and found that it is 3.8C at the base of our kitchen units (and less than 0C at the wall at the back if I pull them off), 0.6C at the new wall in the extension near a new external door, and -1.3C at one point on the skirting board (nb. all of these measurements are with the CH on and other points in the rooms are at least 16-20C!). I'm pretty sure that most (but not quite all) of the very cold spots are close to the air bricks for the under floor ventilation, which we have plenty of. The builder definitely fitted underfloor insulation (solid blocks cut to fit the space held in place with netting or something) and away from the edges the floor seems fine.

In the older parts of the house, I had underfloor spray foam insulation done a few years ago and other than 1 very small area (where I think the builders cut away the foam underneath), we're not seeing anything like this.

I've discussed it with the builder and he said that they had to leave a gap around the edges of the boards against the wall to allow for ventilation because otherwise it could cause damp. I have queried this as I thought that the ventilation was about ventilating the undersides of the joists (so I asked where he's worried about damp forming), but he hasn't responded yet. I feel like something is wrong here - surely we shouldn't be getting these kind of temperatures internally, especially with the CH on?

 

[kp00110]

Do you have solid wall construction in the kitchen area? It is not good for the floorboards or joists to touch the wall as it can cause rot, either from condensation running down the walls or damp coming through the wall or up from the ground, atleast in my house. I dont see why you couldnt use some spray foam or expanding foam to fill the gaps however as that would stop the cold bridging and direct moisture contact between would and walls?

 

[M R]

kp, thanks for the response. The walls are all brick cavity walls - the kitchen area that I'm talking about was extended a few decades ago - I think it is traditional brick inside and out and the new extension is traditional brick on the outside and bigger, concrete block bricks on the inside (see photos). I was wondering about spray foam or pushing in some long foam sausage things that I've got hold of, but worried that if I seal it I'm going to cause some problem that I haven't thought of. I've attached some photos of the extension during construction that show the joists in case it is any use, but I don't have any from the kitchen floor replacement.