Garage conversion build techniques

[finch123]

Hi there, I'm looking for some advice on doing a DIY garage conversion but have a few questions... I have a diagram of what I am hoping to achieve in case it is not clear from my explanation!

We have a part integral garage which can be accessed by a door from the kitchen, we would like to make this into a utility room type area. The garage ceiling has a bedroom above it and is already plasterboarded and artexed so I assume that nothing more will need to be done here.

The existing exterior facing wall is a cavity wall so I'm thinking that this can just be plastered as can the 2 existing interior facing walls. I need to build a timber stud wall to divide the new room from the rest of the garage, I was planning on using fireproof "pink" plasterboard on both sides with insulation in the middle.

The concrete floor needs raising so I was thinking timber joists placed width-ways across the garage floor, insulated inbetween the joists and then chipboard over the top?

Does this all sound sensible so far? If so then I have a quite a few areas I'm still not sure on:

- Would I build the stud wall first, fixing it to the concrete floor or would I build the timber raised floor first and fix the stud wall on top of this?

- What sort of damp proof membrane do I need over the existing concrete floor and where exactly would this go?

- How can I best ventilate this space as it will have no windows, do I need some kind of trickle vents built into the stud wall or perhaps an extractor fan or both vents and a fan???

Here is the diagram. Thanks in advance for any help!

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[finch123]

I've just realised the vent through the stud wall is a stupid idea as that wall is supposed to be fire resistant as it faces what remains of the garage. Any other ideas? It will need some ventilation as it will probably have damp clothes in there from time to time.

 

[^woody^]

You're obviously doing this without b/regs approval then, as it would fail on means of escape.

You should fit a mechanical extract fan if its going to be a utility - vent it out the gable wall

I'd build the wall off the concrete floor, not off the new floor

Polythene as a DPM

 

[finch123]

Hi there Woody, many thanks for taking the time to look over my post.

I would like to comply with building regs to avoid any issues if we ever sold the house. Would putting a fire door in the middle of the stud wall into what remains of the garage be an option?

With regard to the DPM, where does this go? Does it go directly onto the existing concrete floor and then put the joists and insulation onto it or does it go over the joists and insulation but under the chipboard flooring? Also what happens to it at the edges, does it have to overlap the walls and be covered with plaster?

Sorry for so many (probably stupid!) questions!

 

[^woody^]

Means of escape guidelines generally require a window or door to the outside, or an exit onto a hallway which leads to an external door. Even a door in the partition would effectively be leading to another room, which may not be acceptable.

Lay some 1000Ga polyphene on the concrete and form an upstand up the wall to DPC level, and then install the joists and polyphene on this.

 

[finch123]

Thanks for the advice re: door for building regs. Hmm, sounds like I really need to rethink this. Thanks Woody.

 

[noseall]

have you thought about drainage?

 

[finch123]

have you thought about drainage?

For things like sink and washing machine etc? We currently have a washing machine in the garage which is plumbed into the downstairs loo drain (small room on the diagram behind the back wall of the garage) so I was thinking a sink waste pipe could head out that way too. Would this work?