Dave, if you haven't already had a look at my 22x12 workshop, might be worth it :-
https://www.ukworkshop.co.uk/forums/view ... hp?t=15651
I've literally just finished putting the final touches to my shop, i.e. painted the inside and started to build the cabinets along the sides. If you'll bear with me, there are a few lessons I learned along the way that might help you.
As you'll see from the photos, the whole thing sits on a breeze block wall, with 4 air vents in. I didn't bother putting insulation underneath the 22mm chipboard flooring. I have holes for electric sockets in the floor, and when lifted, there's a force-9 gale, which I'm actually glad about as it means there's plenty of veltilation to keep everything nice and dry.
Even though there's no insulation under the floor, an oil-filled radiator on it's lowest setting is plenty to keep the shop cosy. That's because I spent a lot of time any money insulating the walls (120mm wool) and roof (70mm compressed wool) as much as I could afford.
I made the mistake of putting a vapour barrier on the outside, trapping the moisture in the wall. To counteract this, I then had to put another vapour barrier on the inside, with the insulation in between. Although this obviously helps with thermal and sound insulation, it's probably a time bomb. If I don't move in the next 5 years, I'll think about taking the shiplap off and removing the external barrier.
The underside of the roof is clad with tongue and groove pine. I didn't treat these in any way, again down to time and cost, so hopefully everything will expand and contract uniformally. Again, there's an air gap between the ply roof and the insulation, allowing plenty of air movement, and all that nasty condensation to be sucked out
The walls are then clad with 18mm chipboard, mainly because I wanted something I could physically hang units from, and to help with the sound proofing. After some filler and a couple of coats of paint, it's really looking pucker.
You can see from my pics that I managed to pick up 4 double glazed windows from under £100. Those on the 'public' side of my shop now have sticky-back frosting on to keep out prying eyes, while still letting in most of the light.
You say that you want to go for skylights rather than windows - is this for security or wall space. I would highly recommend getting as many windows in as you feel you can - it really does make a difference to how the room 'feels' and will make it a joy to work in. I made the SWMBO as bird table for Christmas, which sits about 6 feet from the window, so I can sit and watch the squirrels on the table whilst waiting for my glue-ups.
Part of my planning permission stated I has to paint the outside in a 'dark' colour, so I went for a dark-brown Ronseal fence treatment. I don't know if it's because the shiplap is smooth or the way I applied it, but it's peeling badly already, even though it's not been on that long.
By the way, because I had so much grief with my planning permission, I had to halt progress for a few months, and left the ply roof uncovered. This was a BIG mistake, as I've now found it undulates badly. It's a shame really, because the dark red felt tiles from Wickes I put on really did make it a nice building to look at.
As soon as I sealed the building and added heating, I moved my cast iron tools in. At the point it was important to sort my insurance, but I was very surprised that my current provider, Barclays, would not cover the contents, even if I offered to pay for it. The building is covered as part of the normal policy, and contents up to about £5K, so I'll have to find another company just for the shop contents.
Like you, I wanted some overhead storage. I purposely built the shop without any trusses so that I had the full height to swing 8 foot boards round. I then added 3 4"x4" beams across the width, that would turn hald of the length into a loft space. I wa amazed at how these beams bowed, so had to attach 10mm steel stiffners (not cheap) to help. Even though there isn't much weight on there yet, there's considerable load on the walls, which have a double header (thank goodness).
I made the mistake of placing one end of the joists above the window and another end above the door. I can't begin to say how this worries me, and expect to come in one day to a bit crack. The morel of the story is, make sure you fully support any joists from floor to ceiling.
At the last count, I has around 24 double sockets around the walls, 11 single flouresent lights, 2 external lanterns, and a few other bits. Needless to say it was quite a big wiring job, although something I enjoyed doing. I completed the wiring, and pre-agreed with an electrician that he would come back and give me a Part-P on the work. If you're going to run a new board to your shop, you'll have endless arguments about how it should be earthed. My advice - just let your electrican decide, as he's the one that will sign it off.
I can't think of anything else obvious you should know. I have found my shop is still too small, and I'll be posting back for help and ideas of how to layout the tools, which now seem to be squeezed in
I hope this has been of some help. If you need any photos, or advice, please let me know - I'm happy to help.
Rob.
