Need Advice On Building A Workshop Shed

[charlie123Participant @charlie123]

Hello, I finally registered here after lurking for many years. I have finally enough money saved to build my dream workshop shed. I’m asking for advice on what to look for in a wooden shed;

(1) Does anyone have experience with the plastic honeycomb waffle plate type base? Interlocking plastic 50cm square plates, 5cm high that you then fill with gravel. Are these better than the old method of just putting the shed crossmembers on paving slabs?

(2) I want to get a large and heavy lathe like a 9 or 10inch South Bend (and a milling machine eventually) – do I need to reinforce the floor with double the number of crossbeams and/or double thickness floorboards?

(3) The shed will be 18ft or 20ft X 10ft, with the ridge running north-south. The windows will be on the east side. Should I see about getting a large overhang on the east side to shade the windows from the sun?

(4) Is 80cm a wide enough access walkway for infrequent use between the shed and a wall?

(5) Any other advice from people that have had workshop sheds built? What am I forgetting or don’t know about?

Thanks

[bernard towersParticipant @bernardtowers37738]

Think about a concrete perimeter for machines and benches. mine also has a comfortable wooden centre piece.

[JasonBModerator @jasonb]

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.

[Martin of WickParticipant @martinofwick]

At that size and with uneven loading, a concrete slab. Otherwise there will be differential movement. I have just had to bin a similar sized shed unit laid on paving that had conspicuously bowed in the centre due to settlement!

The unit I used was commercial but of high quality with 2x3s at 14 in centres and 18mm ply flooring. I added another 18mm 26 in ply runner around the perimeter to spread weight of the machines. Filled in the centre with some engineered oak flooring recovered from a skip! Bloody shed has better flooring than the house.

You can use translucent film or cheap and nasty IKEA blinds to reduce glare on sunny days and still benefit from good light on dull days.

Over 15 sqm you are likely to need planning permission and will be controlled with respect to combustible materials if you have neighbours.

Internally needs to have a breather membrane to the outer side and then 50 to 75mm PIR insulation on the inside and inner ply skin. Obviously insulate roof and floor too.

[Neil LickfoldParticipant @neillickfold44316]

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.

[stephen goodbodyParticipant @stephengoodbody77352]

Hello Charlie,

The current edition of Model Engineer (#4749) and the following four editions (#4750-4753) cover this exact subject, in some depth, among my usual waffle. You may want to read those articles before taking the plunge, they cover a lot of things worth considering in your plans.

Regarding your specific questions, I largely agree with the preceding answers: a poured concrete slab laid atop a plastic moisture barrier, sealed moisture and vapour barriers on the outside and inside of the walls respectively, and no skimping on the sound/thermal insulation within the walls and roof.

Again, there are other really important and related considerations covered in the articles.

Best regards and good luck,

Steve

[David George 1Participant @davidgeorge1]

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

[BazyleParticipant @bazyle]

There have been a lot of previous threads on here, often under titles about insulation rather than specifically shed building.
Q1/ Gravel is for greenhouses. There must be damp proof course (DPC) to stop vapour rising. Even a typical garage concrete floor that doesn’t have have a DPC (most don’t) or an existing shed wood floor needs a plastic sheet followed by flooring eg chipboard at least.

Q2/ either lots of extra joists, or boarding or you can cut holes under bench legs and create a solid fill down to the ground. Beware compromising your DPC. Ideal would be 4in reinforced concrete over 4in of insulation with 4in insulated gap between floor slab and wall foundation to avoid a cold bridge. ( yes I know that is rather difficult)

Q3/ High level burglar discouraging windows save wall space for important stuff. Fit shutters for insulation, security, sun shading. Half the time you are in there it is dark outside anyway.

Q4/ If that space isn’t enough for you then you have bigger health problems to sort out before building a shed.

Q5/ Read the other threads on here and articles in ME. DO NOT follow any of that rubbish about ventilating the shed when you are not in it. Aim to make it totally sealed and run a dehumidifier, then enable controlled fresh air supply when you are in there.

[charlie123Participant @charlie123]

What kind of price per square meter am I looking at for a poured concrete floor? Also my landlord might not allow me to do that, so what is the next best thing? I have a hard budget of £3000

[JasonBModerator @jasonb]

Are you doing the work yourself or will the price need to include labour.

If you leave the shed and make it a nice one then the landlord will probably be OK as it will become a “home office” next time he needs to rent it out. But do check first.

[Martin of WickParticipant @martinofwick]

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.

[charlie123]

On charlie123 Said:

What kind of price per square meter am I looking at for a poured concrete floor? Also my landlord might not allow me to do that, so what is the next best thing? I have a hard budget of £3000

I’ve just had a 12×21 foot concrete based poured. I did the work myself.

2x skips for dirt £340

Hardcore was reused crushed brick but would normally be, at a guess about £70 per ton.

Sand £50 ton

Damproof membrane £50

Concrete £500

About £1k in total but it would likely be more if you live somewhere fancy 😄

[BazyleParticipant @bazyle]

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.

[HopperParticipant @hopper]

+1 on what Neil Lickfold said about seal or paint the concrete floor and insulate the walls and ceiling. Much easier to do it during construction than afterwards. As I found out! The sealed or painted floors are so much easier to keep clean but once the shed is full of greasy junk, not so easy to do!

[Nicholas FarrParticipant @nicholasfarr14254]

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.

 

[Bazyle]

On Bazyle Said:

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.

You must use different screws to me. I recently removed some that had been in timber outside for over 20 years, but if you are concerned about them rusting use stainless steel ones or anticorrosion treated ones.

[Nicholas FarrParticipant @nicholasfarr14254]

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.

[JasonBModerator @jasonb]

If the pro is using an impact driver (not drill) then he is unlikely to be using uncoated screws. They will be hardened, plated with pozi or better still torx head. I don’t have a problem getting them out but I’m also using my impact driver with a decent bit.

Also be aware of asking pro’s to nail things together as we tend to get out our nail guns and shoot a few glue coated ring shank nails in which are far harder than screws to remove.

Beware stainless as they are not a sstrong so heads can come off and also easier to chew up the head.

[not done it yetParticipant @notdoneityet]

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.

[jimmy bParticipant @jimmyb]

My shed base was placed on pre-existing slabs, seemed really stable until I put a half ton lathe on it!!

Ended up cutting through the floor and pouring a slab to sit lathe on.

 

Jimb

[Howard LewisParticipant @howardlewis46836]

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

[HOWARDTParticipant @howardt]

Look on YouTube.  Rag n Bone Brown is building one at present and has guide to material prices.  There are a load of others which will give you ideas of how to build and  cost.  I bought a  10X8 from a local a local bespoke manufacturer for £600 twenty odd years ago which I insulated and boarded inside with 18mm t&g floor and t&g walls, still looks as good as when it was put up.

[Martin of WickParticipant @martinofwick]

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.

 

[Chris CrewParticipant @chriscrew66644]

“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.”

Absolutely agree with that. I had a wooden structure at my previous residence and it was never very satisfactory. If you don’t want to go to the expense, and the hassle of getting planning permission for a brick-built structure, then the next best thing is a pre-cast concrete sectional structure. Relatively cheap, durable and erected by the manufacturer as part of their delivery service, all you need to do is put a solid concrete base down. I chose a 21′ x 13′ garage specifying I did not require the up-and-over door at the time of ordering and  then built a ‘site office’ front into the aperture. The building has performed well for nigh on 25 years now except that I had to put a steel roof on 50mm x 50mm purlins, after about 12years, over the original corrugated ‘asbestos’ roof with loft insulation in between. The interior walls are not insulated in any way but the floor is 13mm plywood laid on a membrane topped with a cheap laminate. I do keep an old convector heater on its lowest possible setting 24/7/365 which stabilises the temperature, its always at least comfortable to work in during the colder months and keeps the rust fairy at bay.

[JasonBModerator @jasonb]

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.

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