Roger Mills (aka Set Square) wrote:

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?

Well if you went for cavity, then the inner leaf would typically be some
sort of insulating block - ok ish for fixing to but not ideal. If you
went for single skin with a studwork frame stuffed with PIR foam then
you could clad it all in ply which gives you an easy way to fix anything
anywhere. Probably work out more pricey than blockwork though.

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?

I would expect if you laid out a grid of rebar and wired it together
before pouring the screed it would be plenty strong enough. It is not
really carrying the load of the cars - it just needs to spread it a
little before it is transferred to the jablite (or whatever you use). A
quarter of a tonne (each wheel) over say 1m^2 ought not make a
noticeable impact on the insulation.

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?

Flat roof with exposed beams would suggest a warm deck construction -
quick and easy. Nothing to stop you from pitching it a little either to
get better run-off (or use steepish firrings). Tiles and a pitched roof
would probably look nicer though - again you can do a warm deck type of
construction with those IIRC. Have a poke around either the kingspan or
celotex site I have a feeling they had an application note showing a way
of doing this.

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?

You could argue that if building control are not involved you can do
whatever you like ;-)

Some questions that need thinking about first though: Is the building to
be joined to the house or some distance from it? How were you planing on
heating it? What sort of workshop tools do you expect to want to use out
there?

Having come out with a power budget, add enough contingency to it to
make sure you cover any likely future use. If you are going to the
hassle of digging a trench for a SWA you may as well make it a big one
since the cable costs will be negligible in the grand scheme of things.
It is also worth thinking through what happens under fault conditions,
so for example what is the implication of losing the lights should you
trip the power circuit with a power tool etc.



--
Cheers,

John.

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