Couple of Q's regarding garage conversion

[steveb1964]

Planning to convert our garage to increase the size of our kitchen and to also provide a downstairs shower room.

Existing garage is joined to our house, flat roof, single brick and the floor is 4 inches below the floor in our house.

Plan is to remove the roof and installed a tiled pitched roof with cavity trays. We then need to raise the floor to match the level of the floor in our existing kitchen. Is the best way to do this to install wooden floor joists and insulate with something or to raise it using concrete?

Next we would insulate the walls. I’ve been told that the best way and most cost effective way to do this is to build a timber frame on the wall and then plaster board and put some form of insulation between the two?

Is the above OK from what people can see or is there a better way to do it?

Thanks

 

[ChapiTheBricky]

how much does the floor need to be raised by

 

[steveb1964]

how much does the floor need to be raised by]

4 or 5 inches

The floor in the garage is currently about 4 or 5 inches below the flooring in our house

 

[ChapiTheBricky]

Never done a job of this type but I would build a stud with osb, put breather paper on the cavity side of the osb, fill the stud with insulation(kingspan type) then sheet with vcl plasterboard. As for the floor you could insulate then screed timber floor works too though.
Ps stick another dpm down first just in case the current garage floor doesn't have one.
Like I say I've never done a conversion of this type before though

 

[steveb1964]

Thanks for your help

 

[Deluks]

Build one or two courses of bricks around the perimeter under where your stud walls will go. You can then lay a dpm over the existing floor and lap up over the bricks and under the timber. That way you have created a 'swimming pool' type affair which will resist any moisture from beneath. Sit insulation boards with t&g chip or plywood on top.
However, wet areas such as kitchen/shower/bathrooms are better with a solid concrete floor. You don't have the height for this in order to insulate to regs so may have to dig down anyway.

If your existing floor is solid maybe you could design so that the shower area is here, as well as sink/wm/dw?

 

[ChapiTheBricky]

you should vent the cavity too, does anyone have any ideas for tying the stud to the existing masonry?

 

[stuart45]

does anyone have any ideas for tying the stud to the existing masonry?

Untitled

• stuart45
• 12 Mar 2011
• 1

These are designed for retro fitting in timber framed buildings.

 

[ChapiTheBricky]

cheers mate, what are those called?

 

[stuart45]

Those are twistfix timber frame wall ties. Most of the jobs I've worked on where a timber frame has been added to an existing wall such as a stone barn has not required ties as the external walls were already strong enough.
Those twistfix ones are installed the same way as replacement ties for a standard cavity wall.
Tie failure is not so common in timber framed builings in the UK as most of them are quite recent builds.

 

[steveb1964]

Build one or two courses of bricks around the perimeter under where your stud walls will go. You can then lay a dpm over the existing floor and lap up over the bricks and under the timber.

If the garage already has a damp proof course would this be needed?

However, wet areas such as kitchen/shower/bathrooms are better with a solid concrete floor. You don't have the height for this in order to insulate to regs so may have to dig down anyway.

The current floor where we want to extend in to is 5 inches below the existing house floor. It does appear to have a DPC in garage and builders have said they can either put a timber framed floor and insulation down or insulation and concrete. I did ask if any of the floor would need taken out to get the height and they said no.

 

[ChapiTheBricky]

dpm and dpc are different, for the time it takes to put another(dpm) one in, i would just do it