Wood Floor Or Concrete Slab And Foundation For Your Garage

The foundation is the part of the building that transfers the weight to the ground and keeps it from moving around. The floor is the part that you stand or park your car on.

The 3 most popular foundation and floor combinations are…

  • Mono pour
  • Stem wall with concrete slab, or wood floor, or no floor
  • Wood floor on pressure treated skids or concrete piers

Building codes and the characteristics of your building site will dictate which of these options you can and can’t use.

Mono pour

This is the combination I’m most familiar with it. The concrete foundation and floor are framed and poured at the same time.

It’s popular in moderate climates where there isn’t much cold or ground movement. And it’s only suitable for reasonably flat building sites.

Stem wall

A stem wall is a concrete block wall that carries the weight of the building down to the concrete foundation. This is a versatile system because it can go far into the ground below the frost line. It is also useful for sloped building sites.

It can be used with a concrete floor poured inside, or a wood floor, or no floor at all.

Wood floor

A wood floor is a good option for economy and ease of building. Simple carpentry skills are all you need to build a wood floor where as concrete is much more difficult to work with. But a wood floor requires more long term maintenance than the concrete.


And a wood floor can make the building portable. If you plan ahead and build with double trusses and studs and build the floor in 2 sections you can cut the building in half and transport it in smaller pieces. Or else just move it whole.

Portable buildings are often taxed at a lower rate, or not taxed at all. Which can save you $$$ in the long run.


A sturdy wood floor can easily hold the weight of a couple of full sized vehicles. Though I wouldn’t recommend parking a tractor because they can be extremely heavy.

2×6 floor joists at 16 inch on center with pressure treated 4×6 skids on 48 inch centers, on blocks or post on 48 inches centers will make an adequate floor for most cases. 12 inch centers for the floor joists would be even stronger.


The simplest foundation is pressure treated skids resting on solid concrete blocks. This is adequate for a fairly solid and level building site if ground movement or wind isn’t an issue.

Otherwise you would bury wood posts in concrete a few feet in the ground and attach the skids to them. You can build on a very rough site or for extreme weather with this foundation.

Check the finished floor for quality

Whether you build the floor yourself or paid someone to do it, you want to check it to make sure of exactly what you have.

If you know the imperfections in the floor ahead of time you can make some adjustments in your framing to counter them. Otherwise your walls might not fit properly and you will never know why.

The 3 things you want to check are:

  • Size
  • Square
  • Level and straight


Pull a tape along each of the 4 sides to make sure the floor is the correct length and width.


Just because the size is correct doesn’t mean that the floor is square. Pull a tape from corner to corner to check the square. If the 2 dimensions are the same then it’s square. If it’s not you will have problems with the trusses and roof sheeting.

Level and straight

Finally you want to check that the floor is level and the surface is straight and flat.

Pull a string along corner of the slab to make sure the edge is straight. That it doesn’t bow in or out, or rise or dip. Do this for all 4 sides.

Then pull a string line from corner to corner across the middle to see that it doesn’t dip or rise across the rest of the slab. You can also pull a string across the middle of each side for more confirmation.

Straighten and clean the j-bolts

Go around with a hammer and straighten up the j-bolts. Put a nut on it or use a block of wood so you don’t damage the threads. Also clean any concrete off the threads with a wire brush.

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