Change to extension ceiling

[NickB_99]

Hi,

Looking for some advice on potential changes to our extension.

Moved in recently and looking at options for some remodelling.

I'm not sure I've got all the terms right, so I hope I get the idea across!
The extension is on the rear of the property. It is a single storey and a pitched roof leaning against the original back wall of the house.
The ceiling in the extension is flat, plasterboard secured to the ceiling joists (the horizontal parts).
We would like to increase the light in the area and considering if this ceiling can be converted to a vaulted one, just one sided, to follow the line of the rafters. Then we'd like to add two velux windows. Is this possible?

I'm not planning doing any of this myself and looking at some research first before inviting quotes.
I can imagine if you take out the horizontal ceiling joists, then the pitched rafters won't be strong enough alone and will need reinforcing first?

If it ends up requiring a lot of the extension to be re-built/roofed then will be prohibitively expensive.

Advice appreciated!

 

[PrenticeBoyofDerry]

Like you said it would depend on, whether the existing structure requires the extra support via the ceiling joists, but it could be doable if not. You will need to insulate the pitched roof.

 

[NickB_99]

Like you said it would depend on, whether the existing structure requires the extra support via the ceiling joists, but it could be doable if not. You will need to insulate the pitched roof.

Thanks for the prompt reply PBOD.

Extension was built about mid 90s. Based on your experience, if you were to guess, is it more likely that I'll find extra support is required, rather than not?

Alternatively, any tricks to access for inspection?
The ceiling is swirled artex with coving up, so I expect I would make a mess if I accessed from below.

 

[PrenticeBoyofDerry]

It would be a complete guess!
Who knows how the design was constructed, what is the span of the extension?

 

[NickB_99]

It would be a complete guess!

Fair enough, just wondered

Who knows how the design was constructed, what is the span of the extension?

Width of extension is across two rooms with a stud wall in between - Total 7m50 plus stud.
The depth of extension is 2m50.

 

[PrenticeBoyofDerry]

I would guess you should be okay!

 

[NickB_99]

Thanks PBOD.
Will get some quotes/estimates.

 

[Doggit]

Some pictures would help, but if I've worked things out correctly, you've got a pitched roof outside, and a flat ceiling inside. What's the difference in height between the top of the outside pitched roof, and the inside ceiling. And if you tap the ceiling, can you work out if the ceiling joists run backwards towards the rear wall.

The roof joists should be the same thickness as the ceiling joists, so you're pretty much transferring the ceiling from the ceiling joists to the roof joists. I think the current regs would requires 130mm of celotex to insulate the ceiling, so you may need to add a couple of inches to the roof joists, put in 100mm of celotex, and the 42.5mm of insulated plasterboard over the joists. You'll be taking out a couple of joists where the Velux windows go, so the joists either side will get doubled up to add the extra strength necessary, but yes, it's all doable. A good builder may well be able to do it without taking the pitched roof off, but having said that, it may well have to come off to have a breather membrane fitted under the tiles, and to provide an air gap.

 

[NickB_99]

Some pictures would help, but if I've worked things out correctly, you've got a pitched roof outside, and a flat ceiling inside.

Yes, exactly.
Will try for some pics tomorrow.

What's the difference in height between the top of the outside pitched roof, and the inside ceiling.

And if you tap the ceiling, can you work out if the ceiling joists run backwards towards the rear wall.

Can check tomorrow.

The roof joists should be the same thickness as the ceiling joists, so you're pretty much transferring the ceiling from the ceiling joists to the roof joists. I think the current regs would requires 130mm of celotex to insulate the ceiling, so you may need to add a couple of inches to the roof joists, put in 100mm of celotex, and the 42.5mm of insulated plasterboard over the joists. You'll be taking out a couple of joists where the Velux windows go, so the joists either side will get doubled up to add the extra strength necessary, but yes, it's all doable. A good builder may well be able to do it without taking the pitched roof off, but having said that, it may well have to come off to have a breather membrane fitted under the tiles, and to provide an air gap.

Thanks for the information, makes sense.

 

[NickB_99]

Some pictures would help, but if I've worked things out correctly, you've got a pitched roof outside, and a flat ceiling inside.

Image

• NickB_99
• 22 Feb 2016

Image

• NickB_99
• 22 Feb 2016

What's the difference in height between the top of the outside pitched roof, and the inside ceiling.

And if you tap the ceiling, can you work out if the ceiling joists run backwards towards the rear wall.

The height difference between top of pitch and inside ceiling is 1m20.

Had a tap around the ceiling, but not obvious about joist direction. Just sounds pretty hollow!

 

[NickB_99]

View media item 97172
And inside view

 

[Doggit]

you should have no problems with what you want to do. the roof will need stripping for the job, but it can all be done quite easily. Best of luck with the job.