Building a garage & gym - wall options & costs

[RobM77]

We've just had planning permission granted for a combined double garage and gym. The whole structure is 13.5m long and 6.3m wide (85m^2), with the garage taking up 7.5m of the length and the gym the other 6m.

Does anyone have any suggestions for wall construction? Obviously we'll be asking the opinions of the builders who quote for us and the planners, but I'm keen to hear from people with experience of living with a garage. I'm assuming that our basic choices are single blockwork, cavity wall (block & brick) or insulated blocks, and then plasterboard or external wall insulation options on top of that. All I can seem to find on the web are pleas from people with cold and damp garages wanting to improve them, rather than advice for someone starting from scratch. The outside will just be rendered to match our house, so no worries there about having attractive bricks on the outer layer etc.

The garage will be for keeping cars that don't weather outside. I currently have a 2-Eleven (open, so no roof or windows etc) and will hopefully keep a single seater in there in the future. I'll also want to be able to work in the garage all year round without the frozen fingers I've traditionally associated with garages in winter. The gym is also for all year round use, although mainly in winter.

For costs I've heard estimates from as little as £200 per square metre right up to £700 per square metre, so I'm assuming that the above options vary wildly in cost?

Any thoughts or experiences much appreciated - thanks.

[RobM77]

Thanks for the suggestions. We'll definitely be going for something under the floor. Good point on the doors too, I hadn't thought about that. For the walls we're tight on space inside and out, although obviously it's pointless having space if it's too cold to use, but I think this might rule out a proper cavity wall. We're currently considering insulated blocks and insulating plasterboard inside - the outside will be rendered. Hopefully that'll be enough?

[RobM77]

FlashmanChop said:

Assuming it is of brick construction I would go for a beam and block type ground floor buildup, using a plasmor block (aglite) and the same 100mm block in the walls, 80mm cavity, including 50mm ecotherm and brick outer skin. Same block means you are not messing about with different blocks on site

Thanks. Currently we're down for a single skin of concrete blocks rendered, so no cavity...

[RobM77]

Thanks Fergus. I'm beginning to wonder if we should have cavity walls judging by your post, others, and the research I've done so far. I haven't got down to doing the thermal calculations yet, but I'm wondering if I should.

Incidentally, your garage works out at £383/m^2, which is pretty decent. I could do much of the work myself too, but I earn more per day than a builder charges and don't get annual leave (or paternity leave!), so it would probably make sense for me to go to work instead, although I could leave finishing touches for me to do at the weekends, such as flooring or even the plasterboarding and interior insulation.

[RobM77]

Mark Benson said:

Have you considered SIPS for the walls? Seems to me that they'll give you all the insulation you'll need and be as narrow as a single skin of blockwork.

No, but thanks, I shall research them now.

[RobM77]

Thanks for all your thoughts. I've found a U value calculator online and done some research on the thermal properties of various materials, along with their cost and thickness. I've come up with the following wall construction, listed from inside to outside:

Standard Plasterboard 12.5mm (U=0.14)
Celotex Board 25mm (U=0.02)
Thermal concrete block 100mm (U = 0.13)
Render 20mm (U = 0.73)
U = 0.43 W/m^2K (comparable to a house, which is more than good enough for what I need).
Total wall thickness: 157.5mm

We'll also add something under the floor and ensure that our garage doors are decent, so thanks for your thoughts on those (they're going to be quite large doors, so insulation of those will be very important).

[RobM77]

Happy Jim said:

RobM77 said:

Thanks for all your thoughts. I've found a U value calculator online and done some research on the thermal properties of various materials, along with their cost and thickness. I've come up with the following wall construction, listed from inside to outside:

Standard Plasterboard 12.5mm (U=0.14)
Celotex Board 25mm (U=0.02)
Thermal concrete block 100mm (U = 0.13)
Render 20mm (U = 0.73)
U = 0.43 W/m^2K (comparable to a house, which is more than good enough for what I need).
Total wall thickness: 157.5mm

We'll also add something under the floor and ensure that our garage doors are decent, so thanks for your thoughts on those (they're going to be quite large doors, so insulation of those will be very important).

If that really is comparable to a house then all houses would be built like that - if you are OK with that then great. If it was my choice I'd go standard cavity wall or if feeling brave then SIPs plus external insulation cladding (as in Europe).

Rgds

Jim

We don't really have the room for a cavity wall, thus the original question. Sorry, I probably wasn't clear enough when I said 'comparable to a house'; what I meant was that building regs state a maximum of 0.35 for a house now, and period stone houses are around 0.9 to 1.0 (I found a study of period homes in Scotland yesterday), so we'd be in the ballpark for thermal insulation alone. A modern home with cavity walls will probably comfortably exceed 0.35 for thermal insulation, and yes of course, that wouldn't be viable to achieve with a single layer of blockwork (you'd end up with a total wall width wider than a cavity wall, plus it would cost a huge amount more), plus there's damp levels to consider and other considerations that result in the standard modern construction methods for homes.

[RobM77]

Inkyfingers said:

For a free standing garage, I think that going all out on insulating the walls will be a bit pointless when you add a huge great garage door, that, even if you go for a well insulated and fitted one, will always be a weak point. Particularly if you actually want to open it occasionally!

It's a very valid point, which is why I asked the question in the first place rather than just relying on the U values; I'm interested in people's experiences with living with a garage.

What my Dad's done to get round this problem is to make a seperate workshop section to his garage, so he's built a stud wall right behind where the cars go with a decent door for access. I used to work on my racing cars in the garage bit (single skinned brickwork) and it was horrible in the middle of winter. I used his workshop bit for engine rebuilds and even on a winter's day it was quite comfortable with just a single skin of standard house bricks and a 20mm gap to standard plasterboard, plus a couple of small heaters of course. I'd like to recreate his environment with two large garage doors, which is obviously a tricky thing to plan for on paper! The blockwork and render construction is a given, because blockwork is cheap and render matches the house, and I thought adding the insulating foam board behind plasterboard on the inside would be a nice touch for not much loss of interior space. The option is a cavity, but I'm worried about the space it'll take up.

[RobM77]

TA14 said:

Why is the wall width so critical on a 6.3m wide garage?

I wouldn't say it's critical, but my parents' garage was 6m wide and it really wound me up with the lack of space down the sides of the cars for jacking and working on hubs, brakes etc.

[RobM77]

VxDuncan said:

Another thing to consider is the practicality of the finished space. Personally I'm so glad I built with solid concrete blocks as they are very strong and easy to hang heavy things like garage shelves off. Thermolites aren't. Down side is massive thermal mass if you are trying to heat them.

That's a jolly good point, I hadn't thought of that, thank you. Part of the reason for me clinging on to width is to accomodate bikes and boards on the walls on the road car side of the garage (never again over my track car, I picked up far too many bumps on the head and scratches on my Lotus from my bikes..). In my last house I hung everything from the ceiling to free up clear wall space, but it obscured the lighting, but of course the lighting could be hung lower, rather than fixed to the ceiling.