Attic conversion and cold-bridging

[pju]

Hi Everyone, I plan on insulating an attic space and need a little advice.

Here is a picture of the room.

IMG_0135

• pju
• 6 Oct 2015

Attic space

I'm planning on insulating between the rafters with 50mm Celotex, and up to 50mm insulation over the top of that. I then plan on plaster boarding.

The question I have is this: Once the plasterboard is up against the brick wall, do I have to use a type of sealant at the join where the plaster board meets the brick? Or will skim do the job?

I'm concerned about creating a cold-bridge at the edges.

Thanks for reading this.

 

[freddiemercurystwin]

Are you a terrace, end of terrace or detached? The walls need to be insulated too unless next door have already converted their loft. Is the roof membrane traditional felt or a breathable type?

 

[^woody^]

What about the cold bridging of the rafters?

Or the insulating of the wall?

Or the building regs?

 

[pju]

Hi freddymercurystwin. I'm mid terrace, the walls are not external. Traditional felt. With 50mm insulation between the rafters there will be a 50mm gap between the insulation and the felt.

 

[freddiemercurystwin]

Then to avoid condensation problems on the rafters you need continuous eaves and ridge vents. The walls should be insulated or insulating the roof alone will be counterproductive.

 

[pju]

Hi freedymercurystwin, if you are willing, would you be able to look at some diagrams that I have drawn to better show what I'm working with?

I think that I was a bit sparse with the details the first time I posted!

The room isn't actually an attic, but eaves which are accessed from a bedroom. The bedroom has a door cut through a brick wall into the eaves. Someone has already put a Velux window in the roof. There is a wooden beam/girder(I think it has a more technical name) that runs continuously through all of the houses.

The room at the moment is very cold, cold air comes in from the soffits, and there is a gap at the apex of the room letting air flow into the attic.

Here are the pictures (questions below)

I'm going to insulate between the rafters, and then over the front of them, and around the wooden beam. I will also insulate the brick walls so effectively creating a 'box' of Celotex.

1. Where I need to return into the Velux window aperture, what should I do?
2. I was going to build the stud work resting on the floor boards, then board the floor up to the stud work. Do I have to worry about cold air coming from the exterior void under the floor boards?
3. Where I have Celotex meeting brickwork, and then more Celotex meeting at 90 degrees, is it advisable to use a mastic to joint?

Thanks in advance for any advice.

P.S as for building regs, I will be asking, I just trying to get a sense of the job. I've done a lot of DIY myself, just never anything like this. I've been quoted up to £2000 for this work, and honestly think with a little advice I can do it myself.

 

[cjard]

1 the aperture is wood, slightly better thermally than Brock, don't worry about it/fit a thin skin if you can

2 yes, insulate the bathroom ceiling under where you wrote cold, to keep the warm and cold spaces separate

3 do an ebay search for: gun foam 12. Buy a gun too

 

[noseall]

My neck hurts!