i went with a concrete slab. Timbers on slab so supported along their whole length and a 300mm ctrs not theusual 400 or more. I layer of boards, insulation but battens above the joists and then 22mm flooring ply over that. I also have far eastern machines not heavy old iron.

The honeycomb is more just to stop gravel moving about due to light traffic rather than to give any better load bearing.

Insulation in walls and roof will have more effect on heat gain than an overhang unless you plan on excessively large windows

800mm is OK for access check if there are any regs regarding combustible materials withing a set distance from your boundry.

I found that sealing the concrete, made a big improvement with the workshop environment. I suspect that in my case, the initial concrete floor was put down onto the ground without gravel or a polythene vapour barrier. My new workshop I also sealed the concrete floor with a commercial 2 pot sealer. Insulating the walls and ceiling also helps with keep the room temp above the dewpoint temperature, thus preventing the rusting of things. We also added a breaker board in the workshop with its own breakers for the power outlets and for the 3phase power as well. We placed the power points at about 1.2 m off the floor height. That way they would be above any normal bench height and more convenient for access. Also added a couple of power points in the ceiling near the middle so no walking over cords, with a chain supported drop lead. Has been very handy in deed. I am still to put in  the compressed air circuit. Also used an older kitchen extractor fan, to take away any fumes from things like soldering etc and is vented out the top of the side wall with a louver that shuts to keep the birds and bugs from coming in. In the corner I have an exhaust ceiling fan that vents through the eave and has a light that serves as a guide to it being or not. That takes away any smoke  fumes from turning quite effectively. Gives the room a change of air.

Happy workshop building.

The last shed I have built was on a concrete slab Which was layed on a good hardcore base and damp proof membrane. The floor was good solid plank an a 3×3 frame and solid insulation between the concrete and plank floor. the walls were shiplap covering a solid frame with vapour barrier and inside a layer of fiberglass insulation was covered by tong and grooved plank. The roof was tong and groove outer with soild insulation butween an inside skin of tong and grooved plank all covered by two layers of bitumastic felt outer hot pitch sealed. A gutter and drain pipe system on the edge of the pitch roof collects rain water to water the garden. It has a small wooden double glazed window with inside locks and a solid double planked dor able to access a palette truck. The floor was also covered by a outdoor ply sheet 20mm thick for strength. Not forgeting to install wiring for lighting and sockets as well as mains consumer unit as and when a layer put on.

David

Depending on what part of the country you are, 3K will likely just about cover the cost of the slab. (dig-out, skip for spoil disposal, 150mm compacted MOT, membrane, steel mesh, 100mm poured concrete delivery, shuttering, labour etc).

Next best thing is to stop now before wasting what little money you have on an unsuitable building within which your costly tools and equipment will rust away.

If there is any chance you have to remove the building do not use screws in wood ie do not use any professional who will want to do everything except stir tea with an impact drill. Screws with the head buried in the wood rust and are impossible to remove even the next day. Nails of a sensible size and type for the job can be removed.

Since the shed is so big maybe you can use a tin garage / shed on simple footings that will keep rain off and be a workspace but within that build a small ‘proper’ shed, say 8×6 that stores all the important tools, lathe etc in a dry heated environment.

Hi, my garage is 6.3 x3.2M approximately with an extra part on the right hand side when looking from the front, which is 3.6 x 1.2M, and the floor is made from a chequer plate loading ramp, which was condemned by the insurance company, for various amounts of corrosion in it’s supporting structure, so the floor is a left hand L shape, looking at it from the back end.

The framework was an old site mess room almost ready for the scrap man, but its roof was just made of the semi-circular sections with angle irons tying them together, but I wanted a pitch roof. The original roof was corrugated iron that was way past its best.

This was all sheeted out, but 2 tonne single use bulk bags were cut, to get some large flat sheets, to sandwich between the frame and the outer steel sheets, which prevents condensation. But before the back end was sheeted in, my 2 x 2M machine shop was added to the back left hand corner, which can be seen in-part, under construction in the photo below.

However, I had no more of the ramp left for the floor, so a brick wall was built up, then mostly filled with dirt, rammed down and topped with hardcore, and a damp proof membrane, I then mixed up some concreate and and used some reinforcing mesh, to bring it up to the same level as the rest of the garage. Virtually all the materials were scrap and didn’t cost me a thing, sake for asking for it from my then employer, and the only things I had to buy were cement, a few nuts and bolts, some welding electrodes and some paint, but much of the electric wiring was also scrap armour cable. The sand and aggregate was overburden, which I had to wash the dirt out of and sieve out all the aggregate that was too large, which did take a while to do, but I was a good deal younger then, but the whole thing took 2 to 3 years to do after I got home from work.

Regards Nick.

Hi, self colour steel screws in Oak and Mahogany are prone to rust, even in dry conditions, but generally speaking most screws will undo in most wood, but not always in very damp or wet conditions.

Regards Nick.

When my ‘shed’ was built, it was a 24’ x 12’ sectional concrete garage behind the original brick garage  (which had been shortened when a 3.6m extension was added to the house).

8’ to the eaves and non-asbestos sheeted roof.  Base was 150mm of concrete, over a   DPM, with a 300mm toe.

The wall panels floor to roof at 16” wide.  I think all the measurements may actually have been metric.  The 24 x 12 was the inside measurement so add 6” for outside dims.

I screeded the floor to prevent/minimise any ingress of water.

At one end, I insulated with 150mm rock wool (and 50mm cavity wall insulation in the panel recesses).  The internal structure was of several scrapped garage doors, since insulated further on the inside.  That approx (internal) 2.2m structure has since been extended by a further 2.4m using 100mm celotex panels plus boarding out.  No windows – lighting is far cheaper than heating (and machines, etc are not visible, or as noisy, from the outside)!

The ceiling is also 100mm insulation, which conveniently just squeezed between the wall insulation and the roof joists.🙂  planks were laid on the steel roof supports to provide support from above.  There is more insulation above those planks

That lot has served me well for over thirty five years with minimal heating in winter and quite cool in the summer – as long as the door is not left open on really hot days.

Current winter heating is by desiccant dehumidifier, mostly running a couple hours each night, and occasional supplementary heat using an almost 4kW chinese diesel fuelled air heater (supposedly rated for 5 chinese kW).  The electric heating/dehumidifying cost, at present, would amount to just over 6p/day.  Never had any condensation or rusting, thank you very much.🙂  Machines are often quite cold in winter but the heater warms the air in a very short time at full heat.

You will find a concrete floor to be hard on the feet, and cold. So think in terms of raising your feet off it with sectional plastic or rubber mats (Although these can be costly) I did find some 1 metre square rubber mats at a “Toys R Us”, which were comparatively cheap. The ones from Cromwell Tools, were expensive being industrial quality.

If all else fails, go like industry used to, and use duckboards, to keep your feet insulated from the cold floor.

My shop is roofed with sheet rubber (Neoprene) It lasts longer than felt.

Do not spare the insulation in the walls or the roof.  At worst, it will reduce temperature fluctuations, and condensation. At best you will be snug, and hopefully, rust free.

To reduce the risk of condensation, and rusting, include a little ventilation. A SMALL fixed vent, at floor level, and another, preferably in the diagonally opposite corner, should be the same They don’t need to be large!

You mentioned windows. You need to ensure that they are secure, preferably with either a cover that can be securely fixed or some form of grille.  The door should be capable of being securely locked (I asked for a 5 lever lock, but actually got a 6 lever in a secondhand fire door)

If a bolt, fix it with coach bolts with the nuts on the inside, and use a GOOD lock.

It is worth fitting hinge bolts.

Mine were just woodscrews, with the head turned off, screwwed into the back of the door, using a drill chuck. In this way, even if the hinge pins are accessible, and driven out, the lock and hinge bolts prevent the door being lifted out.

You will have a lot of valuable machines and tools in there, so safeguard them!

For power, my shop has a ring main, with a lot of double 13 Amp sockets (The one feeding the VFD is suppressed, to prevent any nasty harmonics being fed back into the mains)

When it is frosty, a small tubular heater keeps the temperature just above the dew point. With it being well insulated, a thnermostatically controlled fan heater soon brings it up to a comfortable temperature.

HTH

Howard

A shed is where you keep the lawnmower, spades and shovels, next years onion sets and disused bicycles. A workshop is where you keep expensive / valuable machinery. The OP needs a workshop.

You can purchase a ready made ‘shed’ structure and adapt it, but a quick trawl will reveal that at the size required a suitably solid, tanalised quality unit comes in at well north of 2K. Sure you can buy cheaper, but a unit with 7mm cladding on 25mm frames would be  a waste of money. Then ground works and insulation/internals and electricals have to be added.

Off the cuff, DIY using pressure treated timber you are looking at at least 1K for 15mm TG / shiplap cladding 0.5K for framing 3×2 at 300 to 400 centres, .5K for floor barding at 18mm,  1K for wall and roof boarding 12mm and then everything else like roofing materials, insulation, membranes, doors, windows, electricals, certification, planning ground works etc. on top

The problem for the OP is his budget is tight. If he can acquire the primary materials for free, construct the unit from scratch and can do all the labour, himself then he has a chance on the stated budget.

Oh well looks like I have got it wrong and won’t be able to do any decent work in my shed. At least there is no value in the far eastern machines it contains!

Shed does the job for me and if I can produce medal winning models in it then that can’t be too bad.