On 29/04/2012 18:26, rmwebs wrote:
I'm basically planning on buying a shed, and converting it to an office.
I know that its likely cheaper to just build the whole thing yourself,
Its often more expensive to build yourself, but usually because you
would not pare down the material specs to the same minimal levels as
used by commercial producers.
but I really am not confident that I could do that, so have decided to
go down the conversion route.
It not actually that difficult to diy...
I'd like to start with something like this: 'Suvi 212 Log Cabin -
Summerhouses& Log Cabins - Garden Sheds& Buildings -Gardens - Wickes'
(http://www.wickes.co.uk/suvi-212-log-cabin/invt/218595/) or this:
http://tinyurl.com/7a3radx
Which I'll then insulate, and basically I want the final finish to be
plaster-boarded internal walls, with a good thick insulation all around,
ad I'll be working in it year-round.
ok...
The annoying thing is that pretty much every 'high-street' shed is
really awful quality, and very expensive. However at this stage I'm not
sure I could undertake a self-designed/self-built one as I have never
done anything like this before.
Sounds a bit like the first workshop I did:
http://www.internode.co.uk/workshop/phase3.htm
I'm really looking for some advice, mainly for the insulation and damp
proofing. From my understanding, if I take a box-standard shed like the
one linked to above, is the following correct?
1. Wrap the internal walls , roof and floor in a damp-proof material
such as celotex. (How do I go about venting this, and does the air vent
just need to go through the celotex, or all the way through the internal
plasterboard?)
Celotex are makers of a insulation product (well several in fact). They
specialise in PIR (Polyisocyanurate) Foam, which is a ridgid foam that
give very high insulation values. Often foil coated on one side or both
(for better radiant heat reflection and also as a vapour barrier).
You basically want a vapour barrier any place that warm moist air from
in the building could reach the cold fabric of the building. (where it
could condense and cause rot). You could either rely on the foil on the
insulation (and use a foil tape to cover all the joints), or could use a
plastic membrane like Visqueen sheet (cheap from a builders merchant)
which you could fix under the plasterboard.
The outside of the shed is unlikely to be airtight, so you could leave a
small gap between the cladding and the insulation to allow some airflow
on that side (to allow the cladding to dry on the inside).
If its for year round use you will also need to think about heating and
possibly cooling. A split unit air conditioner / heat pump might be the
solution, since it will heat, cool, and maintain a comfortable humidity.
Or for a less sophisticated solution, and extractor fan, and a wall
mounted fan heater.
2. Add battens as you normally would for a wall, get internal wiring in
place, so the electrician can then just hook it up to the shed's fuse
box (the electrician will be doing all the stuff he has to, but I'd be
ok putting the plug sockets in place ready for him)
The wiring can be the last bit done before the plasterboard goes on...
you can cut a channel in the insulation and sit it in that such that
when the plasterboard goes on, the wires are in contact with the
plasterboard (this will allow them to shed heat better, and hence not
require such a significant de-rating due to the effects of being
insulated. (alternatively you could surface wire after the PB - depends
on how neat you want it)
3. Insulate the walls (at this stage I have no idea what type of
insulation I should be using. Advice?
PIR foam as above. 50mm of it will give you the same performance as
100mm of rockwool. Its also rigid enough that you can do away without
extra battens in many cases - screwing through the PB, then the
insulation and into the existing studs.
4. Add plasterboards over insulation and fix in place.
5. Roof: Add insulation (again, no idea what type) followed by
plasterboards
Same as the walls if you are going to do the underside of the apex
against the rafters. If installing a level ceiling, then you could layer
rockwool etc on top of that like a traditional loft. (only reall
advantage of that would be its slightly cheaper)
6. Floor: Add internal batters, with insulation, followed by ply (or
should it be mdf?) flooring, which will be covered with laminate at the
end.
No need for battens, the insulation will be not crush under the sheet
materials. 18mm WBP ply would be strong and durable.
7. Door: Once the floor has (I assume) been rased due to the internal
insulation, I'm guessing a few inches will need lopping off the bottom.
You need to be careful here, in that if you trim the bottom of the door,
you may also need to raise the threshold so that it still reaches it!
Depending on how the floor is done you could insulate under the whole
shed first.
Also note that heatloss through the floor will be less than elsewhere,
so you could use thinner insulating boards. It would also be worth
looking at Marmox boards - those are probably strong enough that you
could dispense with the wood layer on top, and put your laminate down
directly.
I could have this all majorly wrong so any advice would be appreciated
greatly. I've been searching high and low for some decent info, but a
lot of the places only cover US sheds, and while there are a few
similarities, the construction of them seems very different with a 'farm
barn' style that we dont really have in the UK.
You seem to be pretty much on the right track anyway...
Getting back onto the subject of a completely custom / diy one. I think
the biggest problems I have is A) the plans and B) the roof. I'd have no
idea how to plan it, and I'd be worried that the roof wouldn't be strong
enough.
If you can build a stud wall, then you can make a shed.
http://wiki.diyfaq.org.uk/index.php?title=Stud_wall
Various shed ideas:
http://wiki.diyfaq.org.uk/index.php?title=Shed
What size is this going to be? Unless its going to be massive then its
unlikely to be an issue. Even 2x2 framing is likely to take the roof
weight and that of a adult climbing on it in most typical shed sizes.
I helped a former neighbour re-roof his garage once... that had 4x2
across the (nearly) 3m span on a flat roof and that was more than adequate.
Failing that, if in doubt, post your design ideas here, since plenty of
us have built similar things and will be able to comment from experience.
--
Cheers,
John.
/================================================== ===============\
| Internode Ltd -
http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/