[ms660]

If they are still around I would be going to one of the following, Truro Sawmills at Penhallow, Penstraze Sawmills near Chacewater or Cornwall Wood Treatment Services at United Downs, not sure what they are like now but I know that going back just a few years they would saw timber to the dimensions you wanted.

I was in the home grown timber game once upon a time and was sawmilling as well as building sheds etc, some might not agree but here's my method for workshop shed walls inside to out...Interior wall finish (plasterboard/timber based board etc)>Vapour barrier>Insulation> Racking board> Breather membrane> Vertical battens fixed to studs> Cladding, very solid very weather proof.

As a personal choice for timber cladding I always think that shiplap looks more tidy than feather edge, having said that I was in a position to mill my own feather edge back then, 5" was the choice with a 1" overlap, my fence panel slats were cut from 5" stuff as well. You will find it an advantage to pre drill the cladding at least for fixing the ends of the boards, it will eliminate the risk of the board splitting at the ends when nailing, just one fixing across the width of the board is all that's required, any more and it stands a good chance of splits developing after a while.

If using feather edge cladding it usually comes in (unless custom cut) 100mm or 150mm boards, 150mm is better as you can give it a good overlap without using piles of boards, I would recommend a 1" overlap, pre drill for the end fixing nails at a distance of 1" up from the bottom of the board insert nails part way then you can hook the board onto the top of the previous one and the overlap is automatically set, don't drive the nails home too hard, for shiplap the same distance (1")up from the bottom is ok as well.

I would make sure that the underneath of the floor joists are at least 4" off the ground/base, 6" minimum would be my choice.

Lawrence.