Filling a cavity on a side extension

[akist]

I have built a single story, flat roof, side extension to the main house, approximately 9m x 4m.

When we were building it (both house and extension were built at the same time) I did not think, and did not block off the cavity wall which is really an internal wall.

That means there will be cold air circulating from the surrounding cavity walls and taking away heat.

I would like to block off this internal cavity so it does not communicate with the adjacent external cavity walls.

Here are some photos

The first photo shows the cavity wall from the main house. There are two doors leading to the flat roof section. I can look into the cavity from there.

The second photo shows a photo I took from the door into the cavity.

I am thinking to get a foam spray company to fill it in for me. But it may be very expensive.

 

[blup]

Fill it with insulation.

How do you build a house and an extension at the same time, isn't it just a house?

Blup

 

[akist]

Fill it with insulation.

Not easy there are wall ties everywhere and the access is quite narrow, that is why I thought of using spray foam. But I would need quite a lot, so I'd need some sort of industrial machine, if there was one for hire.

How do you build a house and an extension at the same time, isn't it just a house

It is a flat roof structure tacked on the side of the house, under the gables. So it looks like an extension, even though they were built together.

 

[cdbe]

Drill a few holes up the sides and spray some canned foam in.

 

[^woody^]

If you have cold air circulating between internal cavity walls and external cavity walls, you've built the house wrong anyway, and should be dealing with that.

 

[akist]

Drill a few holes up the sides and spray some canned foam in.

That is exactly what I will do as i was quoted ridiculous prices for a gap fill...

It is about £5 per can of foam. I wonder why they do not sell larger bottles.