Building a Workshop

Welcome! Forums General Woodworking Discussions Projects Building a Workshop

Viewing 14 posts - 1 through 14 (of 14 total)
  • Author
  • #136303

    I apologise if this post is in the wrong forum.

    I’d like to build a workshop in my back garden (it doesn’t require planning permission) but I’ve never done anything like this before. I have two questions I was hoping someone could help me with

    (1) I would really like the shed to be 20′ x 14′ but how big does a workshop really need to be?

    (2) The actual timber shed construction seems to be relatively straight forward as most seem to be constructed the same way. I am though, having some trouble deciding on a foundation. This is what I’ve considered:

    (a) Placing the timber joists directly on the ground, but that’s just inviting damp into the shed.

    (b) Digging to a depth of around 4″ and filling with gravel and tamping it all down

    (c) Digging to a depth of 4″ in filling with concrete, but ready mixed sends the price up to just over £300

    (d) Placing the wooden joists on top of dense breeze blocks – this seems to be the better choice as it will cost no more than £90 to £100

    Not sure if it’s relevant, but my garden has a high clay content

    Any advice?

    Thanks all

    "Sawdust? I think you'll find that's man-glitter."

    Salko Safic

    A big venture ad your lucky you don’t need approval I’m not an expert at this but I do know you’ll regret it down the track if you don’t lay concrete.
    The Lost Scrolls of HANDWORK
    (Hand tool only woodworking magazine)


    I think you may be right Salko

    Also, even though it will be more expensive I think it will be easier to apply because it’s ready mixed

    "Sawdust? I think you'll find that's man-glitter."

    David R.

    Don’t know where you live, but here in Germany we usually dig 60-80cm/25-32″ for a concrete foundation to be below the frost line. I’m planning on having a shed constructed, too and it will probably have point foundation with steel H-anchors which will take the timber frame construction. This neatly separates the wood from the ground. Mine will have to be more modest, though, I don’t have space for anything bigger than 3x4m (10’x12′).

    Good luck with your build.

    from Germany

    George Bridgeman

    I’ve done this myself, so will pass on my experience…

    If you’re in the UK, you can go up to 15m^2 without planning permission, and there are different rules for roof height depending on where the building is going to be located (2.5m or 4m depending on how far from a boundary you are). It’s called Permitted Development. If you’re going outside those limits, you technically need planning permission.

    I laid a concrete slab for the foundation (around 12″ thick, if memory serves); I blogged about it here:

    Although it’s the much stronger option, you probably don’t need a solid slab, and could maybe get by with using large concrete patio-style slabs. Just make sure they’re solid and level – if one of them breaks with your shop on top, you’re in trouble. I don’t know if breeze blocks can substitute for slabs but if they can, they may make life easier.

    The clay content of the ground won’t help – it just makes digging harder!

    Hope this helps. I’m happy to answer any question I can.


    "To know and not do is to not know"


    Thanks George

    I’ve been reading up on concrete online and apparently I need 3″ of it, over 3″ of hardcore rubble. It will cost just a little more than £300.

    As for the clay, yes that could make digging a chore, but once done, I’m hoping it will also be added stability for the shed. That said, the concrete should be taking care of all that.

    "Sawdust? I think you'll find that's man-glitter."

    Eddy Flynn

    Hi Mark, firstly good luck with your build, my workshop is 14’x 9′ and I find it to small and end up setting up a temporary bench on the lawn out side the shed although if it wasn’t a dumping ground for the whole house I might have enough room, as regards to the foundation the more stable the better, you don’t have to dig the clay out you can use shuttering and just remove any lawn or vegetation, that is if you don’t mind a step into you workshop, if concrete is used remember to put plastic tubing in for you cabling /water, I’ve used high density concrete blocks also in the past and they work fine (remember to put a DPC between the block and floor joists) ,if you go with concrete you can use that as you workshop floor saving on timber costs (I recommend you level and flatten to the best of your ability as a rough texture is a nightmare when cleaning up) good luck I hope I haven’t given you more problems to think about .Eddy

    Eddy .. Liverpool, Merseyside, UK


    Hi Eddy

    That’s a good idea, using the concrete floor as, well, the floor. Have to say I really hadn’t thought of that. Definitely something to ponder.

    If however I do place wooden joists atop the concrete, do I need to lay down some fabric to aid resisting damp?

    "Sawdust? I think you'll find that's man-glitter."

    Matt McGrane

    I’ll vote for a concrete floor as well. One thing to consider is that when chopping on a bench you want it to be as immovable as possible. Any vibration will take force away from your work. My time shop is in the garage with a concrete floor. When I chop a mortise or a dovetail, it’s over a leg and there is very firm support all the way to the ground.

    Not sure what to do for the vapor barrier, though, or even if it’s needed.

    Matt, Northern California - Started a blog in 2016:


    Good advice Matt

    Thank you

    I’m hoping I don’t need any extra cover on the concrete floor to be honest

    "Sawdust? I think you'll find that's man-glitter."

    Matt Sullivan


    I built a 16′ x 10′ workshop several years ago. Now I was I had made it larger in all directions. With a 6′ x 3′ workbench, a Shopsmith, small table saw and an embarrassment of disorganization I have very little room for working. One thing I’m glad I did was including a large barn-style door which glides on overhead rollers. This makes it easy to get more light and space quickly. I also built it on a concrete slab. Since this part of my yard gets soaked when it rains, I made the concrete pad 6″ rather than the standard 4″ thick to keep the water from entering. I wished I had not broom-swept the concrete while it was wet. this caused it to be very rough and difficult to clean. I would rather have a smooth polished concrete surface. Good luck with yours!



    Thanks for the tips Matt

    "Sawdust? I think you'll find that's man-glitter."

    Maurice Villari

    Just a word of warning about building on clay soils, they heave with wet and dry weather.
    I would ensure good drainage all around the perimeter to keep the soil as stable as possible.
    As far as size is concerned, I have never met anyone that thought their workshop was large enough as you tend to expand to fill a void.

    Good luck with your exciting project.



    Thank you for the advice Maurice

    I’m hoping the 3″ concrete base on top of the 3″ of quarry scalping will offset the affects of weather.

    "Sawdust? I think you'll find that's man-glitter."

Viewing 14 posts - 1 through 14 (of 14 total)
  • You must be logged in to reply to this topic.