Extension with cold wall - should this have cavity closers or similar?

[Diybeginner5]

One of the rooms in my house is an extension done by previous owner.

Looking today I can see into the cavity from the extension which is a garage. Should this have cavity closers or similar to stop airflow? Also is there a way to top up the cavity wall insulation at it seems low down?

I might get a builder in but keen to understand if easy to diy it or what I should check / ask a builder!

 

[Diybeginner5]

Just to say I’m now unsure how I would fit the closer as the wall heights are different?

 

[Diybeginner5]

I’m struggling to find anyone to come and fix this for me - anyone know of any good builders in the Gloucester / Cheltenham area please?!

 

[Deluks]

From your pictures, it's hard to see what's going on.
Is it a room in the house or just a garage?

 

[^woody^]

I suspect a can or two of expanding foam may sort you out

 

[Diybeginner5]

I’ll try and get some more photos but essentially this is an internal wall in my garage - the brickwork is the external wall before the house was extended with a garage wrapped around it. There is now a flat roof above the wall but the cavity as per the other photos doesn’t seem sealed and is only I think half filled with insulation. The bedroom wall directly behind the wall you can see in this photo is lots colder, I’m assuming because the cavity is open and effectively acting like a single skin wall? I’m keen to get closed up/ insulated if possible but don’t know how…

 

[Diybeginner5]

If it helps for context this was previously a normal external wall. The property is a bungalow - the wall is now inside a garage but now appears to have this open cavity because the flat roof of the garage is now on top of it. Does that help at all?

 

[cdbe]

How much access have you got? When I took my roof off I found that the CWI had settled quite a bit and was able to manoeuvre some cavity batts in.

 

[Diybeginner5]

hmm hard to say does this photo help? I have enough I can get some insulation in but I wondered if the insulation would then need sealing up to stop the air getting into the cavity? Also what insulation would I use as it looks like fluff vs loft roll insulation?

 

[cdbe]

Use 50mm cavity batts, they can continue up to the roof decking to close it off.

 

[Diybeginner5]

Oh thanks! Where the insulation is currently do I need to brick that up to stop the airflow?