On Thu, 2 Mar 2006 22:01:58 -0000, "Roger Mills \(aka Set Square\)"
wrote:

As you will know from my earlier thread "Size of a double garage", I am -
planners permitting - hoping to have a detached double garage built at the
front of my property.

I have established that, provided it has a floor area not exceeding 30 M^2,
and is made of non-combustible material, it will be exempt from building
regs. This is fine from a fees point of view, but also means that it won't
have a BCO making sure that it's built properly!

I would like to be able to use it from time to time as a workshop, without
requiring too much heat input - which means that it requires a reasonable
degree of insulation. I would appreciate your views on this.

WALLS
Should they be of cavity construction, filled with insulation - or single
brick with some exotic material or other fixed to the inside? What is the
effect of the choice on the ability to fix things to (e.g. shelves) or hang
things (e.g. ladders) on the walls?

I think it's perhaps as broad as it is long.

My starting point was a garage with single brick walls and pillars at
the front and periodically along the sides. I installed stud frames
next to the walls except at the pillars using a gap of about 25 mm
behind. I put 50mm Celotex in the frames and taped them with foil
tape. I then applied 18mm ply across the whole lot. Where the
pillars are, there is just a gap behind the ply. This doesn't make
the garage any narrower from the perspective of getting a car in if I
ever wanted to do so since the width is limited by the pillars at the
front. The other advantage of this approach is that I can fit things
to the walls anywhere without having to tit around with plugs.
For anything heavy like my dust extractor, I can screw to the studs.

The double cavity wall approach would achieve virtually the same
thing, I think. You could compare the insulating properties of each,
but I don't think that there's a great deal in it since the insulating
material is the main determining factor.

Fixing things involves plugs each time unless you do something like
I've done in the past. That is to fit Spur shelving rails at
intervals along the wall for most of the height of the wall. You can
then easily put shelves in and move as needed. Near the top of the
wall you can install a French cleat. This is basically a piece of
timber - e.g. about 70x35mm with a sloping edge at the top. It slopes
back towards the wall. You fit similar pieces the other way round to
the backs of cupboards, boards to hang tools on and so on. A spacer
piece of similar depth is attached to the bottom of the cupboard/board
The items can then be moved around as needed.




DOOR
I rather fancy an automated roller door - like the ones made by Henderson et
al - with double skin aluminium which is foam filled. Does anyone have any
experience of these? Are they robust and reliable? What are their thermal
properties?

I've been researching these to do a swap when it's warmer. The ones
by Henderson et al. are much of a muchness and I was not impressed
with the quality. Plus, I don't care much for the roller slatted
look which strikes me as rather industrial looking.

I'm gravitating towards sectional doors at present as being a better
compromise between functionality and aesthetics.

In terms of manufacturers, Hormann seem to have a much better quality
than the others, but the price reflects that.
If I went with that, I would probably attach Celotex to the inside as
I have with the current (up/over) doors.





FLOOR
It will have a concrete floor. It would be nice to have some form of
insulation (rigid foam or whatever) under the concrete - but is this
practical, bearing in mind that it needs to take the weight of two cars?

Can't help you with that one. The floor was already there and I
wasn't about to dig it up. I did do the calculations of heat loss,
and provided that the walls and roof are insulated, it isn't a great
deal - possibly 1kW or so on this size. I never have cold feet when
I'm working out there, although I do have some anti-fatigue mats to
stand on as concrete does get hard after a while. It also helps if
you drop anything.




ROOF
I'm currently undecided about a flat (felted) or pitched (tiled) roof.
What's the best way of insulating it? I'd rather like exposed beams from
which I can hang things - and to make use of the available storage space if
I go for a pitched roof - but still need to get some insulation in
somewhere. Any thoughts?

Yes. I already had a pitched and trussed roof - felted and battened
same as a house. The storage space is very useful. I fitted 50mm
Celotex across the tops of the rafters leaving the depth of them to
provide ventilation. I suppose I could have fitted 25mm between
rafters and 25mm over the top but it wasn't worth it. I used long
drywall screws with large flat washers and screwed through the Celotex
into the rafters. Gaps were taped. It's arranged that the space
behind the Celotex connects with the space behind the wall framing. I
then put in soffit vents between each pair of rafters to ensure
ventilation. The joists were then boarded throughout apart from
between one pair where a wooden loft ladder is fitted for access .
Behind it is a large removable panel in the floor that provides access
to hoist large but not heavy items up and down. I installed an
electric hoist above the hatch for the purpose.

Not insulating the "ceiling" is deliberate. Usually the ladder and
access trap doors are closed which keeps heat below that level rather
than letting too much warm air convect into the roof space. However,
it does mean that there is some warmth and than is sufficient to
prevent metal items from rusting etc.




ELECTRICS
Haven't really thought about them yet, but I shall need some light and
power. I assume that they will have to be Part P compliant, even if the
structure is exempt from building regs?

My only comment here is to allow for plenty. SWA cable is cheap.
Digging trenches is a pain in the botty.

I put in three compartment trunking around the walls and have run
wiring in PVC singles rather than T&E. Circuits are wired as radials
with one circuit per side. I then have individual 16 and 32A
circuits with IEC 60309 outlets for machinery.

Lighting circuits run in conduits to fluorescent fittings with
electronic ballasts in rows and intervals across the ceiling.

Consumer units are cheap so I put in large ones to accommodate all the
circuit breakers.

I felt that I would rather adopt this approach to make later changes
easier.



--

..andy