Integral single garage conversion- will they have to build another 'internal' wall to line the outer one??

[Erebus]

Sorry if that doesn't make sense, but... our house looks identical to this one:

here - note we have a utility behind the kitchen; they have an open plan kitchen/utility. And theirs is much better decorated than ours...

It is 12 odd years old. We are considering converting the garage to a 2/3 room, 1/3 storage to the front, leaving the up and over door in place.

I know we will need that new dividing internal wall to be fireproof etc, we will need to raise and insulate the floor, but... will we have to get a new, brick wall built immediately inside the existing outer wall or will that be considered 'double skinned' already? If you look at the inside of it, it's breezeblock which implies to me that as the outside wall is brick, it's already 'double skinned' for the purposes of a conversion, in which case, do they effectively just put up battens and attach plaster board to them to 'hide' the breeze blocks?

This ishoo is size, really. IF they have to build another wall inside, then batten and plasterboard it, the new room will be rather small!

Your thoughts, please!

it's an integral garage, I have no doubt that the entire shell would have been built with cavity walls. There is probably insulation built into them as well.

p.s.

OO(not much)I, the inner skin is most likely built of lightweight concrete blocks. Breeze has not been used for many years.

piglet- yes, I'm sure you're right, it'd be concrete blocks, not breeze blocks as such! I guess they were used to make a wall quickly and easily.

The room, being a garage, is currently as cold as a witch's appendages, but that'd be because of having a poorly fitting metal door at one end and a concrete slab for a floor, wouldn't it?!

probably cold because it is draughty, unheated, and has no solar gain from windows.

You can get draught strips for garage doors. I use bristle ones as rubber strip wears out on the concrete. They can also be lined with Celotex or Kingspan to improve the insulation of what is a very thin structure, but light enough not to make them hard to open.

The new dividing wall might benefit from being skinned both sides with insulating plasterboard, and any door might need to be fire resisting. Garage doors are very easy to break in through, so any door in the dividing wall needs to be strong and well-locked like an external door.

Thanks.

We're not planning on having a door between the new living room and the storage area; that'll still be accessed via the up and over door; but I gather the whole wall will have to have some sort of fire rating as the storage area could be used to store say a motorbike. I shan't worry about insulating that area any more than it already is.

if the storage area is very cold, there will be more heat loss through the dividing wall, so at the least, try to draughtproof the big door.

Celotex is a rigid building foam, in sheets, and fairly easy to attach - not a big job, and can be cut with a fine saw or even a breadknife.

Good point, piglet -certainly something to discuss with the builder. I guess that the 'firewall' would probably only be single skinned, wouldn't it? Though maybe more insulated?

The dividing wall will most likely either be built of lightweight blocks, plastered, or a wooden studwork (less likely, metal) frame with plasterboard both sides, and preferably filled with mineral wool insulation.

I don't think I've ever seen a single-skinned firewall. The wood or metal would burn or collapse if exposed to great heat on the open side.

piglet sorry, a bit confused- am I right in thinking what you described i.e "built of lightweight blocks, plastered, or a wooden studwork (less likely, metal) frame with plasterboard both sides, and preferably filled with mineral wool insulation" constitutes a 'fire wall' for domestic building reg purposes? Or is what you've described the wall of "wood or metal (that) would burn or collapse if exposed to great heat on the open side".

So what would a suitable firewall be constructed from, would you say? (I am thinking how thick it'll end up being, more than anything!)

a wall of lightweight concrete blocks, plastered on both sides would do (plaster absorbs heat in a fire, and gives up the water that it is partly made of)

a studwork, or metal lathing, wall with plasterboard both sides (usually two layers) would do

A wooden studwork, or metal lathing, wall with plasterboard on only one side would not do, because it would not stand up to fire on the unplastered side. Since you can't predict which side a fire might start, that's not good enough.

The wall would end up about 150mm thick. The local building control office will have a choice of acceptable constructions, and your local builder will probably have done hundreds of them. Fire regs on garages are quite strict due to the risk of a petrol fire.

Thanks, that's really helpful!

So.... when can you start?