On Sat, 10 Apr 2004 21:31:24 +0100, Pete C
wrote:

Hi,

Nice plans! Might be worth considering 4" rockwool beween 4" joists,
would be cheaper, better and easier to install than 30mm Celotex I'd
expect, though a vapour membrane could be necessary.

It isn't - I've tried it. The problem is that the rockwool tends to
hold on to any water that gets in for whatever reason (e.g. driving
rain against the side for a long time, among others). It is
difficult to support it away from the outer cladding to permit
ventilation. A vapour barrier is definitely needed and will need
to be fitted additionally.

For insulating below a floor it is a PITA because there is no good way
to support it effectively.

I made shed in this way some years ago and ended up ripping out all
the rockwool and replacing it with Celotex.

I've now done three buildings with it, including the garage workshop
and it is extremely easy to use because it stays in place and is
light. A given thickness of polyisocyanurate foam has
approximately 4x the insulating property of glass fibre, and the foil
on both sides provides the vapour barrier.
It is also a lot more pleasant to work with because there are no
fibres to stick in the skin.

THe only slight disadvantage is the slightly higher cost, but in the
context of a project like this and the time taken, it's a no-brainer.



If you set the bricks supporting the floor timbers in cement this will
allow you to even out some variation in the concrete base.

As far as timber goes, it tends to rot at the ends where exposed to
water so dipping these pieces in wood preserver then coating the ends
would be a great help.

Getting everything pressure treated seems like a bit overkill and CCA
treated wood is nasty stuff to work with.

It should certainly be treated with some form of spirit based
preservative if it is to last a reasonable time.






cheers,
Pete

wrote:

Hello all.

This years project looks set to be a large shed at mums place.

I'll be building from scratch, as I want a challenge and to achieve
something better, more substantial and different from the usual stuff.

It'll be about 18' x 8', part potting shed, part summer house, with
covered veranda deck area. There's a CAD render of the design at
http://www.sbriggs.plus.com/shed14.jpg

I have a few questions for the collective wisdom of the group on
construction methods and materials.


The latest thinking on the base is to mount it on single brick pads (on
a large, existing concrete platform), then a 50x100 joist frame, T&G
floor, then the shed structure.

Wall & roof framing I'm thinking 25x75 sawn timber studs & rafters,
50x75 sill & head. Inside skinned with 6mm WBP ply, outside with VT&G
weatherboard. I'll put about 30mm of Celotex / Kingspan on the inside
face of the wall cavity. I'm debating the need to vent the remaining
cavity to the outside, I can easily have a 10mm hidden gap around the
framing at ground & eaves level, and over the roof ridge board. Is this
a good idea? Should I put a vapour barrier in there somewhere? If so,
what to use?

Timber treatment is another issue. While the floor joists will be
tanalised timber, I don't think my local timber yard has on-site
treatment plant, so everything else (weatherboarding, frame, floor etc)
will be untreated red or white wood. I could then paint or spray a
suitable preservative on, but would it really be worth shopping round
and getting the whole lot prevac treated (which adds about 20% to the
cost)?

Any other construction or material suggestions welcome.

Finally, this is grand excuse for compressor and nail gun purchase.
Probably the Axminster £100 compressor (2.5HP /25L /7cfm FAD) and 50mm
brad nailer. Are 18ga brads going to adequate for the cladding?


Cheers all,

..andy

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