Wooden Floor for Workshop?

[devvar]

I am in the process of building a 20'x24' workshop (https://www.garagejournal.com/forum/threads/20x24-pole-barn-workshop.546488/). Current use is general storage, vehicle repair, woodworking, etc. This is currently the only covered storage on my property so it will be used for everything. Long term I plan to build a garage for parking the cars, and another equipment shed for storing tractors, implements, dump truck, etc. Eventually I plan for this current building to become a dedicated woodworking shop. I anticipate maybe 10 years before this building becomes dedicated woodworking space. My question is about the floor. I have very limited budget right now and want to get this building usable as quickly as possible. I am considering two options:

1) Pour a concrete slab. This would be insulated but not heated, probably 4-5" thick. I have never finished concrete before but would attempt to do it myself (with some help from family & friends). I understand the finish will not be as smooth as a professional crew but I think I can get it good enough. I estimate this to cost about $1000 more than the wooden floor below, performing all labor myself.

2) Build a wooden floor system. This is appealing to me for a variety of reasons, including that it will be less expensive, won't require any special skills or equipment I don't have, and could be built in phases if needed. I currently have 3-4 few inches of 3/4" clean stone down. I plan to compact the stone, put down a vapor barrier, and run 4x4 sleepers lengthwise about every 30". I will use double 4x6 where the tires of a vehicle would run to create a solid 12" wide area under each tire track. I would then fill the space between the sleepers with foam insulation board. Then install 2x6 lumber all the way across the top, creating my finished floor. There would be no airspace under any lumber. All lumber would be pressure treated. This floor could be repaired as needed, or even removed in the future for a proper concrete slab if I want

I have a couple concerns with the wooden floor:
- snow or water running off from my tractor or a vehicle parked in there for work getting trapped due to the vapor barrier on the bottom. Should I put the vapor barrier on top of the foam, under the 2x6 instead? Should I run all the 2x6 through my table saw to make tongue and groove boards to prevent bulk water intrusion? Should I use Rockwool ComfortBoard instead of rigid foam? I believe the comfortboard is vapor permeable and would allow drying upwards if the vapor barrier is on the bottom, but is much more expensive.
- structural integrity / stiffness when using a floor jack or bottle jack to raise a vehicle or tractor on the wood floor. I currently work on a dirt driveway so I'm used to the challenges of uneven, soft ground. I don't anticipate this being an issue here, especially using cribbing under the jacks/stands, but I definitely don't want a vehicle falling down when a stand punches through the top layer.

Is the wood floor a waste of time? Am I asking for trouble? I am interested to hear anyone's thoughts who has worked in an old barn or shed with a wood floor

 

[cvairwerks]

A lot of old time machine shops had wooden floors...About 6" long sections of 2x4's and other dimensional lumber off cuts, all standing on end, with wedges on one edge to tighten them up. Perimeter was simply concrete beam that supported the building walls.

 

[WisJim]

Based on my personal experience (or inexperience with concrete), I wouldn't do a concrete slab that big myself. I did build a pole building garage/shop once with a wood floor in the shop half, built on treated 2x joists 16" oc, with treated 3/4" t&g plywood for a floor. The car part was gravel until I hired someone to do a slab in that part. I used fiberglass insulation between the floor joists. I ended up putting galvanized metal flashing all around the exterior edge of the building down about 6 to 8 inches to keep woodchucks from burrowing under the floor. We ended up moving before I got everything done to my satisfaction.

 

[Old tool guy]

Wood floor will be easier on your feet & legs if you stand on it for long periods. If you drop tools they will be less damaged, especially edge tools. If you run electrical or air lines under the floor structure, you can move them if your layout changes.

 

[dscheidt]

Ask your insurance company of what they think of parking vehicles on a wood floor.

 

[devvar]

Thanks for the feedback everyone! Hopefully I can get this put together this spring

 

[rust in the eye]

A lot of old time machine shops had wooden floors...About 6" long sections of 2x4's and other dimensional lumber off cuts, all standing on end, with wedges on one edge to tighten them up. Perimeter was simply concrete beam that supported the building walls.

Streets too; https://www.atlasobscura.com/places/wooden-block-alley

 

[C-S-H]

I currently have 3-4 few inches of 3/4" clean stone down. I plan to compact the stone, put down a vapor barrier, and run 4x4 sleepers lengthwise about every 30". I will use double 4x6 where the tires of a vehicle would run to create a solid 12" wide area under each tire track. I would then fill the space between the sleepers with foam insulation board. Then install 2x6 lumber all the way across the top, creating my finished floor.

I like the idea of a wooden floor for your woodworking shop versus concrete floor. Its use is analogous to fishing out of a wooden skiff versus an aluminum jon boat; the difference in bodily comfort and overall feel and sound is immense.

You need to accommodate about a 3000 Lb load whether it is from a tire load, jack load, or woodworking related loads. Your member sizes and spacing are very light for that. From a shear capacity standpoint a 3x8 #1 SP would be the smallest decking board you should consider (for reference, highway deck planks are 5x10 #1 SP with stringers at < 24" spa). The 4x4 sleepers are too narrow to do their job, and spaced way too far apart for the decking. They should be more like 2x8 or 3x8 pressure treated SP, and spaced at about 18".

Your insulation plan and introduction of water through the floor are at odds. You might want to wait to install the insulation until after the building becomes a dedicated woodworking shop. You can use Type V XPS at 100psi crush rating and place it continuously over your stone and under the sleepers. I also like the idea of biscuits between decking boards to keep the floor planar. The vapor barrier should be draining type like a geotextile if used. Water from vehicles or spills should drain right through to the stone after sneaking though the XPS joints.

 

[JohnX14]

Pour a concrete floor, and hire someone. Flatwork labor is not so much that you want to screw this up trying it yourself. Especially in a relatively small shop.

There is a place for a wooden floor in certain shops. I just don't see it here. If you're doing it to save a few dollars, it seems liek a bad idea. It seems like a bad idea, in any form.

 

[Skiff Builder]

I did a wood floor 32 x 34 garage /shop 10 years ago. Has held up very well (boat builds, car repair, woodshop, etc).
I laid a 4' grid of treated lumber as a nailer , embedded in about 9" compacted road base. Plastic on top, than 3/4" BCX plywood. Stained/ Urethaned.
Poured concrete aprons for 3 garage doors.

The road base holds all the weight! The plywood acts like an easily removable "Paver". No structural framing at all. I did not place foam under.
Building dept and insurance were fine with it. Our home sits above it-used double 5/8 gypsum on ceiling for fire code compliance
Very comfortable to work on, easy clean. Has stood up well to water/ salt/ snow/ sand/ epoxy/ fiberglass. Spills wipe up easy and don't stain.

Glad I did it this way. Good Luck on your project!

https://www.garagejournal.com/forum/threads/new-wooden-boat-shop-floor.357734/

 

[devvar]

The road base holds all the weight! The plywood acts like an easily removable "Paver". No structural framing at all.

You need to accommodate about a 3000 Lb load whether it is from a tire load, jack load, or woodworking related loads. Your member sizes and spacing are very light for that. From a shear capacity standpoint a 3x8 #1 SP would be the smallest decking board you should consider (for reference, highway deck planks are 5x10 #1 SP with stringers at < 24" spa). The 4x4 sleepers are too narrow to do their job, and spaced way too far apart for the decking. They should be more like 2x8 or 3x8 pressure treated SP, and spaced at about 18".

@Skiff Builder is correct, the lumber is not structural. The stone under the wood is taking the load. The 2x6 just spreads that load over a much wider area so the psi is very low. In your example of 3000lb load, placed on a single 2x6 with my max span of 30" that would be a ground pressure of 18psi. If the boards were splined or biscuited together to spread that load, that ground pressure would drop much lower.

You might want to wait to install the insulation until after the building becomes a dedicated woodworking shop.

@C-S-H I think this is probably the right move, make things much simpler and less risk of rot/mold. I don't plan to heat the building for a while anyway. I would fill the space between 4x4 sleepers with compacted stone.

I also think I might scrape some of the stone I currently have out, put down a vapor barrier, then put stone and floor structure on top of that. That way the wood is only in contact with stone that will drain the bulk water

I considered plywood, it would certainly be less labor to install. Especially if I used T&G Advantech or something similar. I think I prefer the look of the individual 2x6 boards, but still not decided there yet

 

[LOW1]

My shop is part of our boathouse which is built over the water with pressure treated lumber and on top of steel pilings and frame. I laid down tar paper and then relatively cheap rough sanded unfinished white oak flooring. Finished with a penetrating exterior oil finish. Used a flooring gun and stainless flooring cleats through the tar paper and into the wood. I am happy with it.