Reply To: Workshop foundation/base
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Hello Rowly, as Rich said, one possible solution is a sand bed with concrete or walk stones or laid on top of it. That is a possible solution for the walk surface but you still have to build the structure and that can take many forms from pole barn construction to a full fledged conventional framed structure to a prefabricated steel building. It would be pointless to anchor any of these to walk stones. Some type of solid connection to mother earth is necessary to resist wind loads and that can be poles in the ground, CMU’s laid on top of a concrete footer or a monolithic pad/footer which is pretty common in the southern US where frost levels are shallow.
Having been a general contractor, I would prefer a poured concrete solution and that isn’t usually hard for a contractor to do. A couple of tips if you go that way though. Concrete should be poured over a gravel bed about 4″ to 6″ thick with a vapor barrier (20 mil polypropylene sheet) on top of the gravel. The gravel acts like a french drain. No form of insulation is needed nor will it really do anything. You can do the forming and gravel spreading yourself. Unless you’ve done it before, I don’t recommend trying to finish lay and finish the concrete yourself. Hire a professional for that. As Sven-Olof points out, concrete suppliers usually have excess material in their trucks that they are more than willing to dispose of but it would be hard to find enough surplus for an entire pour. A 20’x20′ slab will need about 5 yards of concrete and that’s a little over 1/2 a truck load. If you try to do it in multiple pours, you would need to break the pad into sections with expansion joints to avoid having cold joints in the finished floor. Left over concrete can be difficult (maybe impossible) to work with because it’s been in the truck so long. Even expert finishers cringe at the thought of trying to deal with it.
If you decide to build a wood floor just be sure that it has some clearance to the ground, cover the ground with a vapor barrier and any wood touching masonry has to be treated lumber. Insulation can be put in if there is enough room under the floor to work but it really won’t be of much help as long as a vapor barrier is put down and the crawl space is ventilated. Load wise, a properly designed wood floor would have no problem with the weight of the machines we use if it has the equivalent of a 3/4″ subfloor with a 3/4″ hardwood walk surface laid perpendicular to the joists. Cost wise, a wood floor would be the most expensive option though. And don’t worry about weeds – worry about termites. Be sure the ground has been treated before any concrete is poured. Hope that helps.