Insulating my new shed roof, walls & floor.

[sweeneyuk]

I have just had a 15'x10' apex roof shed erected today. construction appears to be pse 2 3/4" x 1 3/4" treated studwork. treated 13mm shiplap walls & 15mm t&g roof. All sits on 18mm treated timber base on treated timber bearers approx 2x2.

I had a concrete base constructed before hand which the shed now sits on but base is larger than the shed. I have now read that the bearers should sit on a dpm in this case but its too heavy to change now.
Also would've like to lay an extra row of bearers in opp direction before it went down but didnt get chance.

before i ask about insulation i noticed a poss issue today in heavy rain. Moisture was being drawn up into the timber studs at the base & into the edges of the timber floor boards.
Seems maybe the water was running off the roof then splashing up off the concrete base on to the sawn edges on the floor boards which then absorbed along the boards a few inches into the shed.
The boards are treated & once the rain stopped they started to dry out.

Not sure how to rectify this or if this is normal. Maybe some guttering will catch the rain & stop most of it. Maybe i could construct a small skirt around the base?

Anyway onto insulating the shed. with the moisture in the floor issue just mentioned my plan for the floor was to:
1. board out floor with 25mm polystyrene or similar.
2. lay a thick dpm membrane.
3. lay a t&g floor system.
4. Lay lino
Should i use osb over chipboard or is there a better product for this?

for the ceiling & walls (studwork being 2 3/4")
1. use a superfoil quilt type insulation & tape it up to act as dpm.
2. osb or ply board over insulation.

Should i add battens before boarding out?

or should i just batten out studwork for extra depth & use kingspan type boards in between studwork?

Leaving aside windows & doors this will give me an airtight inside space, should i add some vents, if so where?

If i use kingspan inbetween the studwork do i fill the whole space or leave an airgap between the o/s wall & ins or between inside board & ins? will the shiplap vent itself or do i need to add breather holes in each studwork partition?

any advice appreciated

 

[imamartian]

what a complcated post !!

for what it's worth, guttering is a must !!!

 

[mikej2005]

All sits on 18mm treated timber base on treated timber bearers approx 2x2.

I had a concrete base constructed before hand which the shed now sits on but base is larger than the shed.

The shed the previous owners of my house left behind also rests on 2x2" wooden battons on a concrete slab base, very similar to yours.

I'm not sure how old the shed is, but the battons are almost completely rotten due to the water that gets onto the slabs soaking into them over time and this has spread up and into the floor. I can't help feeling that yours will eventually go the same way, given time.

The only way I'm going to be able to rescue the shed from further deterioration is to take it apart and replace the floor and battons.

When I rebuild it, I intend to mount it on bricks, in order to keep the battons up and out of the water - much like this :
http://parker1.co.uk/shed/shed/shed0009.JPG

Are you wanting to insulate the shed simply to keep the water out or do you need to keep it warm for another reason ?

If it's the former, then surely it would be better to make sure the water doesn't get into the wood from the outside in the first place, by making sure it's properly built, sealed and treated ?