Filling cavity left by back boiler removal

[diy_fun_uk]

I'd like to have a go at this myself and, on reading various websites, there appears to be a number of ways to tackle this. I'm thinking of the following, please advise if this approach will do, doesn't necessarily need to be the gold standard / tier 1 approach as long as the end result is reasonable. For info, the heating engineer will be removing the fire and back boiler, leaving whatever's up the flue in place.


1. Re: the flue, if it's literally a vertical hole from the fireplace up to the chimney pot, am I right to assume it's best to attach some sort of mesh to the bottom of the flue to stop insects, birds etc getting access to the cavity?

2. Use 4x2 to create a frame around the cavity, recessed to allow for plasterboard insertion.

3. Cut section of Celotex to size including hole for airflow (is it best to cut the Celotex to fit the entire cavity, or does it suffice for it to fill the 4x2 frame i.e. flush with the wood so the plasterboard can attach directly to the frame?)

4. Fit Celotex into cavity.

5. Cut section of plasterboard to size including hole for airflow, insert into cavity and secure.

6. Fill any minor gaps between newly inserted plasterboard and surrounding wall.

7. Paper section of wall with lining paper ... remembering to cut out section for airflow!

8. Fit vent.

9. Re: chimney pot, if it doesn't have a cap, get one fitted to stop rain coming down but still allowing for airflow?


Am I along the right lines?

 

[oldbutnotdead]

Before you fill the fireplace in it would be a good idea to get the flue swept (to get any loose rubbish down and out while it is easy)

Your mesh ideally wants to be at the top of the chimney (to stop birds nesting in the flue) though that can depend on how you cap the thing

Vent hole in Celotex- put a plastic airbrick in the hole. Don't quite understand the question about size of Celotex- don't bother filling the entire space where the fireplace was. If the brickwork round the fireplace is irregular you might want to think about leaving a 10mm gap between 4 x 2 and brick (use blocks for fixings) so you can fill the gap completely with expanding foam.

Chimney pot- yeah that's about right. If when you get up to the stack you find that the pot is loose, consider removing it entirely and flat capping the flue (allowing for ventilation- air bricks again).

 

[diy_fun_uk]

cheers for feedback/advice. My query re Celotex is should I cut it to fit inside the wooden frame (so it's flush with the front surfaces of the wood) or should it be cut to butt up against the wooden frame i.e. be slightly larger all round.

 

[oldbutnotdead]

Ahh. I'd go for inside the frame (assuming we're talking 70mm thick or similar).

 

[diy_fun_uk]

thanks again. got a chimney sweep company coming out to remove liner, sweep and fit cap for £140 so I'm happy with that. I'll then buy myself a small board of plasterboard, 4x2, insulation board, expanding foam and crack on!