Shed roof - metal on wood

Lotus-eater

I'm planning on buying a shed, (I worked out the cost of building it from comparable materials and building it myself, but it's virtually the same) and changing it to my spec, by mainly adding a few bits of timber here and there and putting in a damp proof breathable membrane.

My main question is the roof, it comes with a 16mm T&G roof, but nothing else, which is great as far as I am concerned, as I wanted something better than felt.
I was thinking about box profile metal sheeting. My question is, do I need to put something between the metal sheet and the wood roof?

If I put the large profile in the air, then there will be a large air gap underneath, but still some of it will be touching the wood, presumably gathering some moisture.

I was thinking maybe some battens first, or something else?

tony6403

Have you thought about using shingles. In my opinion would look much better than metal sheeting.

Lotus-eater

I'm not that bothered how it looks, but as it happens I quite like the green box profile metal sheeting.

The main things I am worried about, is keeping the shed free of condensation and keeping the timbers free of rot.

I'm really struggling to decide on a course of action for the roof and now the walls and floor. So many different avenues of advice on the net.

tony6403

You could treat the roof with preservative and then add your metal sheets.
I doubt that there would be any condensation.

Norman_Castle

Onduline is an option. Avoid condensation with ventilation.

http://onduline.co.uk/

http://www.wickes.co.uk/bitumen-corrugated-sheet-950mmx2m-black/invt/240039/

cyclonebri1

I wouldn't run battens across on top of plywood, they will stop any penetrating rain from draining freely.
On a house roof they run across rafters not solid, so there is always a gap.

Shingles gets my vote.;) Cladding sheets always look a little "industrial" to me.

-taff

yuo can batten vertically and then fill the gaps with insulation if you want to.

Lotus-eater

That's a good point about the penetrating rain and battens, something I hadn't thought of.

I am bit confused about insulation and ventilation. Everyone says insulate and then ventilate, aren't they working directly against each other?

-taff

Insulation basically traps air in a material that slows down the heat/cold exchange but with enough gaps in it to allow ventilation so there aren't any cold spots where moisture can accumulate.

You ventilate rooms to avoid condensation forming inside.

Someone else will be along with a more technical and probably more accurate explanation soon

tony6403

[QUOTE=

I am bit confused about insulation and ventilation. Everyone says insulate and then ventilate, aren't they working directly against each other?[/QUOTE]
This raises the question of how many hours will you be spending in the shed in the cold months. That is to say is it worth the cost of insulating if you are only in the shed for the odd hour or two.
The door and other gaps in sheds and the single glazed / plastic windows might make proper insulation more trouble than it's worth.
Have a look at the present cost of insulation products - a rip off.

cyclonebri1

-taff wrote: »

yuo can batten vertically and then fill the gaps with insulation if you want to.

Which gives exactly the same issue with blocking penetrating rain run off.


If insulation is needed, rigid stuff fixed to the inside would be the best option I believe.;);)