Garage conversion

[NGEddie]

Hey all,
I have a standard size garage attached to a neighbour's garage on one side and with a door through from my kitchen on the other. I'm planning to insulate and plaster board the walls, put in an insulated garage door and use it as a utility/storage space.
All advice welcome!

First step is to put in a flat ceiling with insulation above I'm thinking. Looking for advice on easiest way to do it... ceiling joists? Best way to attach up to brick walls on either side?

Thanks,

 

[RedHerring2]

We need more info' on your garage, e.g. construction materials, style, etc.
Especially the roof.

 

[noseall]

It is either a utility or a storage area.

If you intend using it as a utility then building reg's will apply. The sensible thing therefore would be to insulate/ventilate correctly as to avoid condensation issues in the future.

 

[NGEddie]

We need more info' on your garage, e.g. construction materials, style, etc.
Especially the roof.

Garage is standard teracotta coloured house brick construction, single skin. Roof points in the centre and slopes to front and back. Roof has pretty standard looking tiles and is lined underneath but no insulation.

It is either a utility or a storage area.

If you intend using it as a utility then building reg's will apply. The sensible thing therefore would be to insulate/ventilate correctly as to avoid condensation issues in the future.

Thanks for the info on building regs. I was planning to put the washing machine in there and a radiator, at what point do building regs start to apply?
Assuming I do want to insulate/ventilate to meet building regs, what do I need to do?

 

[RedHerring2]

Insulating the roof/ceiling:
Two choices, insulate between the rafters, leaving a 50mm space for ventilation (and possibly ridge vents needed.) or insulate the ceiling. Do you have ceiling joists? Is the garage roof made of truss rafters? Will you be able to access the loft area after plaster-boarding. Or do you intend to insulate then plaster board? In which case you'll need to support the insulation, if using normal loft roll insulation. Or you can use rigid insulation between the ceiling joists or above them.

If you're going to insulate the ceiling check out any ventilation that will be needed in the 'loft' area first.

 

[RedHerring2]

I was planning to put the washing machine in there and a radiator, at what point do building regs start to apply?

I'd call that a utility area.
You have two choices: (Well three, fees payable for the first two options)
1. Start work on a building notice, assuminmg you know what you're doing and invite the BI round at the first appropriate time. (Not recommended for you for obvious reasons.)
2. Submit drawings/plans detailing how you'll meet the current requirements and wait until the BI has approved what you intend to do. They'll specifiy when they want to visit.
3. Ignore the recommendation and just go ahead hoping that the BI doesn't find out, or if they do, you've done it correctly anyway. (Not recommended for you for obvious reasons.)

 

[NGEddie]

I'm not worried about using the loft space for storage, though guess I should leave an access point just for maintenance reasons. I can't currently see any ventilation points in the roof, I'll need to add some?
I don't have truss rafters so currently nothing at ceiling level, will need to put up joists. The space is 8'2" x 18'2", what size joists would you recommend? Can I screw joist hangers direct into the walls or do I need to run a ledger board or something first?

Thanks again for the helpful advice!

 

[RedHerring2]

I'm not worried about using the loft space for storage,

I don't think there'll be much room up there for storage.

though guess I should leave an access point just for maintenance reasons.

And for laying insulation after you've plasterboarded. Ensure that you're going to have enough manouvering space.
Position any crawl boards before you plasterboard.

I can't currently see any ventilation points in the roof, I'll need to add some?

Check out the eaves, where the roof meets the top of the wall. Is there a small gap there. If not you can provide ventilation several ways:
low level slate/tile vents, and high level or ridge vents if you think you need them, or vents in the gable walls. As long as you have sufficient air flow from one side/end to the other. The regulations call for 10mm continuous gap at eaves, I think. It'll be slightly different for ridge vents or for vents in the gable wall.
Don't use only ridge vents.

I don't have truss rafters so currently nothing at ceiling level, will need to put up joists. The space is 8'2" x 18'2", what size joists would you recommend?

Sorry I've left my timber sizing tables in France so can't advise. I'm sure someone else will oblige. It's 2.498 meters. Does that include the bearing onto the wall or just between walls?
Edit: Silly me, you're using joist hangers!

Can I screw joist hangers direct into the walls or do I need to run a ledger board or something first?

You can screw joist hangers directly onto the wall, except that they normally are supported by the top of the brick, not just screws into the masonry. There is normally a lip on the top of the hanger that hangs on the brickwork. The end of the joist prevents it from coming away from the wall, therefore prevents the lip of the hanger from coming away from the brickwork, i.e. very little play in the length of the joist. I think the regs call for something like 2mm max each end. (Info' may be in the Timber Sizing Tables) You may have to chase out a little of the mortar between the brickwork to accomodate the lip of the hangers. And fill the chase afterwards with some mortar or resin or similar.
Another pitfall to be wary of is that it is very easy to dislodge the top course of bricks. I suspect the only weight holding them down is the wallplate.
Again, perhaps other more experienced and qualified may advise.

 

[RedHerring2]

Just found this:

http://jrpcad.co.uk/Timber_Span_Tables.aspx

So 2.5 metre span at 400mm centres use 120 X 50mm.

400 or 600 centres are easier when boarding 'cos 2400mm is divisible by 400 or 600, not by 450mm.

It wouldn't hurt to provide one row of blocking down the middle. It may not be strictly neccessary, but better safe than sorry, especially using hangars which don't provide quite the same resistance to twisting as blocking between the joists.

Also, notch out the bottom 75mm or so of the joist either end to accomodate the hangar. The boards then sit flush and flat.

Edit; It might be worth costing up 120X50 at 400 mm centres (about 14 joists) compared to 150X50 at 600 mm centres (about 9 joists & 10 hangars less).

 

[RedHerring2]

Another point I've just thought of:
it may be easier to fix your plaster boards down either side of the garage, then lay your insulation down each side while you can easily reach into the eaves, paying attention to any required ventilation.

Then complete the boarding at the centre of the garage ceiling, having worked out the correct spacing for the boards.

Leaving just the down the centre insulation to the last where there's most headroom under the ridge. That's assuming your ceiling joists will span the same direction as your rafters. 'Cos you did say that the roof slopes "front and back"

If the ceiling joists end up at right angles to the rafters, the same principle applies, just apply 'ends' of the garage instead of 'sides' of the garage.

If this is the situation, I did mention crawl boards in the loft. It might be worth fixing those crawl boards to the ceiling joists to act as binders running parallel to the rafters. Again, may not be strictly necessary 'cos your roof has been designed without restraint at ceiling level, but it won't hurt to provide some restraint.

 

[NGEddie]

Thanks RedHerring2, I'll be taking your advice and submit drawings before starting the work. I've been reading the Building Regs last couple of days to be sure I know what they expect.

I'll probably have more questions as I draw up plans. First question is, the regs don't seem to specify how much insulation is required.
How much between/above the ceiling joists?
How much behind plasterboard on external walls?


Thanks again for all the help
Niall

 

[RedHerring2]

I'll probably have more questions as I draw up plans. First question is, the regs don't seem to specify how much insulation is required.
How much between/above the ceiling joists?
How much behind plasterboard on external walls?

270mm is the latest requirement, I think for loft insulation. 100mm between joists, then 170mm at right angles to it.
Perhaps other more experienced/qualified might confirm.

I think the wall insulation is more complex. I think it's a case of meeting certain U values, which will be dependent on your current structure and chosen method. You might also be required to tank the walls.
Again, perhaps others, more experienced/qualified might advise.

 

[DevilDamo]

Just so you're aware, you will need more insulation if insulating at ceiling level rather than at rafter level. If you insulate at rafter level, then there's no reason why you can't install an access hatch between the hatch for additional storage without having to compromise the insulation (if you were to put it) at ceiling level.

 

[NGEddie]

Just so you're aware, you will need more insulation if insulating at ceiling level rather than at rafter level.

Really, why's that? I'll have to look into rafter level insulation I guess. My Rafters aren't very deep so difficult to insulate between them, but I guess can extend them...?

 

[NGEddie]

Hello all, this project wasn't dead, just sleeping...

I've been doing some background reading and planning before putting my money where my mouth is. Need to know if this is looking right and also need advice on a few points along the way. Thanks!


FLOOR
=====
Grind down any high bumps on concrete floor
Thoroughly clean and dry concrete
Paint on a vapour seal/DPM (need advice what to use. Garage is 2.5x5.5m)
Self leveling screed floor (need advice again)
Lay lino - either self adhesive tiles or stuck down with spray adhesive

CEILING
=======
Add ventilation through facia in eaves
Attach 47x150mm ledger board around all 4 walls
2 rows of screws spaced at 300mm into rawl plugs
Joist hanger nailed into ledger board at 600mm centers with 2" nails
47x150mm C16 rated joists cut to be a tight fit and sat into joint hangers
Hammer through joist hangers with 1" nails
47x150mm blockers between joists
Hire a plasterboard panel lifter
Screw plasterboards into Joists using 45mm drywall screws (long enough for ceilings?)
Leaving 600x600mm hole in center of room for loft space access
Insulation between joists and above joists running perpendicular
Plaster finish over plasterboard join and screwheads

EXTERNAL WALLS (trying to follow advice from celotex website)
==============
Breather membrane on external walls (what is this? where to get it?)
50mm Celotex insulation boards along the external walls (how to fix in position?)
Celotex Insulation tape to join insulation board and complete vapour barrier
Mastic to seal around insulation (top, bottom, left and right??)
25x50 timber battens top and bottom
25x50 timber battens at 600mm centers
25x50 timber blockers between battens
Plasterboard pushed flush with ceiling (probably slightly off floor?) screwed in place with 45mm drywall screws
Plaster finish over plasterboard join and screwheads (easier if plasterboard is square edge or tapered edge?)

JOINING WALL
============
Already insulated between garage and house
Plasterboard dot and dabbed directly onto brick wall