Bay window roof insulation

[Randommoose]

Hi,
I've just got a new house, a renovation project. It's a bungalow and the main bedroom is in a front protruding section so has 3 external walls. It is cold and the bay window and its ceiling is mouldy and cold.

Since having the asbestos soffits removed I have realised that the bay window ceiling has no insulation, it is just one sheet of plasterboard and that is it. No wonder it was mouldy and cold! The 3 bricks in an angled shape above the side windows were on top of the soffits so are now loose and hence the plaster inside has cracked as this is just single skin.

I plan to bring the ceiling down in the bay section down to the tops of the windows and out to the wall level with timber stud and PIR boards (2 layers), foamed and taped, ensuring there is a 50mm ventilation gap to the roof. I've attached a basic side plan of before and after. Does this make sense? Should I do this or something different?

What should I do about the angled sides? Remortar the brick to make it secure? Replace with timber studding?

Any suggestions would be great. Thanks!
Moose

ps most of the muck on the walls is wallpaper glue, not anything worrysome!

 

[Ian H]

Your plan sounds good to me. How about a soffit level with the window top returning back to the bricks?

 

[Randommoose]

Your plan sounds good to me. How about a soffit level with the window top returning back to the bricks?

I am putting up all new fascias, soffits and gutters. That photo was just taken before the old stuff was all removed. The soffit will be level with the window top. Though I am finding it tricky to find 500mm wide soffit at the moment! Found a few online suppliers but I don't need 5m and the associated high delivery price so I'm trying to find a local supplier.

 

[Randommoose]

I'll also be removing all the birds nests, wasps nests and installing fascia vent strip, felt support trays and bird comb to do a proper job and hopefully avoid future problems. Will put up some nest boxes in case the birds miss their previous home!

 

[catlad]

Are they going to be central heated bird boxes!

 

[catlad]

Back to your soffit question use hollow soffit cut to the lengths you require, the first bit near the gutter will be
caught and held in place by your new fascia board.
You will need a starter trim at the other end called
an F Trim.

 

[Randommoose]

Any ideas what size timber do I need?

 

[Randommoose]

The whole space is 2640 wide, 180 high (to ceiling level), 680 deep (to window).

Would 50mmx50mm timbers work ok or do I need bigger?

 

[Ian H]

I’d use a treated 3x2 (47x68ish?)

 

[Randommoose]

I’d use a treated 3x2 (47x68ish?)

Ok.

I'm trying to match up the sizes of timber and insulation board (which comes in 50, 75 and 100mm) as I will have two layers of insulation and don't want gaps between them. But 100mm timber seems really long to screw through for the 90 degree corner. But maybe that is normal and there are long screws I can use? All I've ever done before is an ordinary stud wall in 2 dimensions so working out this 3 dimensional shape is confusing me!

 

[Ian H]

I think your 50x50 will really be 47x47. Best to go and have a look what’s in at the timber yard.

 

[Randommoose]

I think your 50x50 will really be 47x47. Best to go and have a look what’s in at the timber yard.

47mm will be fine as it is close enough to the 50mm insulation. I just don't know structurally how big the other dimension has to be. It is only supporting the weight of the timber itself, insulation boards and a normal layer of plasterboard. I have had a look at building regulation span tables but they seem to be working on much bigger spans and I couldn't find if I could lower the timber size for a non load bearing small area of dropped ceiling.
Thank you for your help, I really appreciate it!

 

[Ian H]

Can you attach the 50’s to something that’s there already, wooden lintel or something? Bet it would work if you had some pieces from your new frame upto the extisting.

 

[Randommoose]

I am planning to have a two full long lengths go side to side, one near the room wall surface, one above the window frame (on the brick outer wall). Then short lengths horizontally front to back between these and the most sticky-out bit of the window. And short lengths vertically from the most room-side long length up to the ceiling joists above. I don't think there is a lintel there of any sort but I'll know more once I take off the existing plasterboard.

I've missed the order cut off for delivery tomorrow from the local builders merchant so will either need to hire a van tomorrow or get it delivered on Monday. That gives me a bit more time to work out what to do. The plasterer starts on Tuesday but I will get him to do other rooms first so I have time to build this.