Insulating Single Brick Wall

[knight84]

Hi,

At the back of my kitchen through what was originally the back external door of the house, you step down into a small extension which was added when the garage was built on the side of the house around 25-30 years ago. This room has been used as a storage/utility room. As you enter the room a door on the left leads to garage and to the right a door to the garden

The room is of a single brick construction which had been plastered. Due to elderly relatives visiting frequently i plan to raise the floor level with the kitchen and construct a partition to create a hallway and a downstairs toilet as they are unable to use the stairs.

The room is dry, no signs of damp or water leaking in other then a small patch around a poorly fitted upvc window and an old wooden back door which i intend to replace.

I would like to insulate the room before starting work on the conversion. My question is would the following method be suitable?

1) Remove old paint and plaster from walls
2) Wash down to remove all dust and paint with 2 coats of bitumen
3) Fix 50mm layer of kingspan to the walls with silicon dabs. Tape the joints with aluminium foil tape and use expanding foam around the edge of the boards.
4) Batten at 600 centres using 25mm battens
5) Fix 25mm polyboard insulation between the battens.
6) Board with 12.5mm Plasterboard.

I have tackled many building projects but never insulation. The internet has given me many conflicting answers and i don't want to do something that will cause damp/moisture problems down he line.

I would be very grateful of any advice you could give. Many thanks in advance.

 

[ban-all-sheds]

Don't understand the point of the bitumen.

I would:

Batten the walls, fit foil-backed insulation between the studs, with a bit of an air gap, make sure all of the joints are sealed, and then board over the top.

Pay attention to potential breaches of the VCL (sockets/switches/pipes etc).


DISCLAIMER - the above may gloss over what is required by Building Regulations re renovating a thermal element.

 

[knight84]

Thanks for you speedy reply.

As i say i have had conflicting information on the method to use so wanted to get some more advice first before proceeding.

Sockets wont be an issue as there wont be any in the toilet and the pipes i will run underneath and bring up through the floor boards.

Using your method would the 50mm kingspan i mentioned be suitable?

Thanks

 

[noseall]

You are probably looking at a minimum of 140mm celotex type insulation to bring a single skin structure up to modern reg's standard.

Don't forget the floor and ceiling too.

 

[tony1851]

You are probably looking at a minimum of 140mm celotex type insulation to bring a single skin structure up to modern reg's standard.

Not that much, surely?

 

[noseall]

You are probably looking at a minimum of 140mm celotex type insulation to bring a single skin structure up to modern reg's standard.

Not that much, surely?

One brick thick walls = 40-50mm

1/2 brick thick walls 125mm upwards.

I have yet to see a spec' that has asked for anything less than 140mm i.e. 100mm betwixt with 40mm across.

Don't forget, I don't design I just slavishly follow building control or designers/architects etc.

 

[tony1851]

Don't forget, I don't design I just slavishly follow building control or designers/architects etc.

Then perhaps you shouldn't always believe what those 'experts' say.

Single-brick wall with 70 Kingspan and plasterboard should achieve around 0.30 U-value. (of course it may not satisfy other technical requirements - just considering U-value)

 

[Guitar_man]

In such an upgrade could the VCL consist of just the foil on the kingspan/celotex, or would you need to use foil backed plasterboard as well.
Is an air gap required between the kingspan and the brick wall?