The shop addition was slab-on-grade so I had a full range of choice of how to do the floor. My decision was to split the 45′ length into two parts:
- 10′ of concrete slab flush with the floor
- 35′ of a 2×4 based “sleeper” floor
I wanted to do a wooden floor for the majority of the work area in order to save my knees and ankles in the long term. My old basement shop was all concrete and at the end of a long day I could feel a slight dull ache in my legs. This was in a fit guy in his late 30s so I could tell that something needed to be done.
Other benefits of doing a wooden floor were:
- Less damage to dropped tools
- “warmer” feel
And there certainly are cons:
- Extra cost
- Vibrations from lathe aren’t soaked up
Why the split?
The split concrete area got some raised eyebrows from my builders. It’s more of a long-term insurance policy just in case I wind up needing the firmness & durability that concrete provides. Here are a few cases I could think of:
- Welding area
- I get into metal working and buy some enormous mill & lathe
- The wood lathe proved to be unworkable out on the wood floor
None of the above cases have come true so for now it’s mainly a storage area.
How does the lathe fare on the sleeper floor?
When spinning an out-of-balance piece I can feel the vibrations being transmitted through the flooring.. it’s an odd sensation, sort of like sitting in a rumbly truck. But I haven’t noticed any actual ill-effects from this, i.e. extra chatter in my bowls. I haven’t noticed any difference in behavior as compared to my old shop with its concrete floor.
(for reference, my lathe is a Robust American Beauty which weighs 600+ pounds)
Before I get into the construction of the floor I need to be clear about how the slab was poured. My shop sits on one big 20 x 45 slab, but the wooden floor area is sunk down 6-3/8″ The 10′ area of concrete that I walk on was poured flush with the existing garage floor.
The 6-3/8″ number brings us into what comprises the wooden floor, listed in order of bottom-up:
- Treated 2×4 “joists” laid on their flat sides. In the above image they are the vertically-oriented, dotted-outline lines. There are 4 rows of them on 6′-6″ centers. 1.5″ high
- 2×4 grid on 12″ centers. 3.5″ high
- 1″ tongue & groove subfloor. 1-1/8″ high
- 5mm loose lay vinyl flooring. 3/16″ high
Add up these numbers and you get about 6-3/8″ inches, and by golly those concrete guys hit the number!
My framer did a nice job making the floor nice and solid. The flat joists were power-nailed into the new concrete and also set into place with construction adhesive. The 2x4s on top of those were also set into place with adhesive and then nailed. And guess what, the sub floor was also glued into place.