dust collection and a slab

[lrogers]

We are finally in the new house and my back yard has a spot with no sod just waiting for a shop. I'm trying to work out all the details before I start building (what a concept). Since I have to wait for the bank account to refill a bit, I have time.

The shop will be built on a slab and I plan to have the table saw in the middle. I want to run a conduit through the slab so I can have the power close to saw and not have to step over the cord. I would also like to have a DC branch close to saw so it's out of the way. I'm thinking about running a 4" PVC branch line from the wall drop through the slab, popping up out of the slab by the saw. Any one done this or have any better ideas/suggestions?

[LCHIEN]

I always thought a good idea would be to run a trench in the floor. Make it deep and wide enough for the hose or 4" PVC you want, the wiring can easily fit in the space around the hose if its a rectangular profile.

Put a rabbet in the top of the trench, size it so you can drop a 2x6 or maybe a 1x6 to cover the trench and be flush with the floor so you can walk without tripping and roll carts and tools over it without trouble.

Have one end of the trench at one wall where the DC will be and the you have power outlets. The other end at the center of your shop where the machinery will be, or perhaps run it all the way across so you can DC from tools on the other side of the room w/o resorting to overhead ducting.

With the trench you can add or subtract, you can also put tools anywhere along the length of the trench and you can rearrange the covering board with a miter saw, much more easily than if you concrete in place conduit and piping.

[LarryG]

The optimum solution would be a wood floor, on a crawl space. I am a firm believer that a dedicated woodshop should not be on a slab! With a crawl space, you can get under there and run stuff wherever you like, and rearrange if necessary. Dropped tools will be less prone to being damaged. Wood is warmer to stand on in the winter. Wood will contribute less to tool rusting than concrete. And after a long, satisfying day in the shop, your aging legs with thank you (I can say that because I know you to be about the same, ah, vintage as me). If you intend to remain in your new house for a while, the additional cost of a wood floor will be well worth it.

If that's out of the question, a trench as Loring suggests is next best (but see the note below). Anything that is embedded directly in concrete WILL, sooner or later, one way or another, become a royal pain in the ass. In our projects here at work, we basically do everything we can to keep stuff out of slabs. Electrical conduit is not too bad (assuming you get it in the right place, and can live with that location forever) but plumbing and ducting can really cause problems ... corrosion and leaks for the former, mold and blockages for the latter.

(One thing to consider about a trench: it will require formwork, and some kind of lid, and by the time you get through spending the money needed to do it right, you'd have a sizeable down payment on that wood floor.)

[BobSch]

On the trench idea — how about lengths of preformed floor drain? Comes with a cover and everything.

[gary]

According to Bill Pentz; you need 800 CFM at a table saw and you need'll 6" duct to get that volume. He also says you need 3000 fpm velocity through horizontal ducts and more through vertical ducts to keep them from clogging.

Here is his site: http://billpentz.com/woodworking/cyclone/index.cfm -- be prepared a lots of reading.

[lrogers]

good ideas and food for thought on all points. Larry, your point about the wood floor and old legs is very well taken. I guess for a wooden floor/crawl space I'd need a perimeter trench for a footing and then a couple courses of block. that might be a little easier to do-it-yourself than a slab. guess I could even excavate the area under the shop to give the clearance I would need and still keep the shop floor level doen lower. More thinking to do........

[don_hart]

Actually Larry if you are considering a wood floor then I would consider post and beam construction. This would not require that you dig a trench, pour a footer and lay block.

[JR]

If you did the wooden floor idea, it's not necessary that there be a crawl space, is it? You could treat it like a computer-room raised floor.

You could screw plywood panels to a 2-by frame, and just pull up the panels when you need to make a change.

JR

BTW - I like the idea of a wooden floor just for the "rightness" of clunking around on it in a woodshop.

JR

[pierhogunn]

second the raised floor idea, I work on one all day, and it sure is nice to be able to hide things down on it, Check around, you may be able to find a used raised floor. Just start shopping around, you could probably find one... (course this would probably cost more than wood on a crawl space, but dang you could do a lot with it)

Dan

[LarryG]

I've heard that surplus computer room floors can be bought for a song these days, but I don't know whether they could handle the point loads imposed by big, heavy stationary tools and workbenches. My guess is that they couldn't.

[Stytooner]

Larry, I don't know if I pointed it out when you were here, but I have a trough in the concrete section in my floor. It houses a 4" pvc line now, but its stuffed with insulation board, so it could hold a 6" line if needed. It runs to the center of the shop. I also have a quad recepticle in the center of the shop floor right next to the pipe outlet. It certainly is nice having it done this way.
For the cover on the trough, I just used some more rigid insulation and a plank of Hardi panel. Its rigid enough to roll over some, but when I find some grating, it will be replaced.

In the time that I have had this in the floor, 3+ years, I have had to clean it out only once. I was drilling 2" holes in lexan with a Forstner bit. It made some rather large unruly shavings. I use a holesaw now. Cleanout was accomplished with compressed air and took about 10 seconds. It gave the force needed to help it all along to the collection barrel. Good luck with what you choose. I can't wait to come see it when you get it going.

[gary]

quote:Originally posted by LarryG

I've heard that surplus computer room floors can be bought for a song these days, but I don't know whether they could handle the point loads imposed by big, heavy stationary tools and workbenches. My guess is that they couldn't.

You'd be wrong. I've rolled IBM Mainframes weighing tons across computer room floors in large data centers and never had any problem.

[Tundra_Man]

quote:Originally posted by LarryG

I've heard that surplus computer room floors can be bought for a song these days, but I don't know whether they could handle the point loads imposed by big, heavy stationary tools and workbenches. My guess is that they couldn't.

We've got some server racks on our suspended floor that are heavier than anything I'll ever have in my shop. My guess is that one of these fully loaded units weighs in the 800-1000 lbs range, which for a 2x2 footprint is a whale of a load. Now imagine a whole row of these lined up...

I think the computer room floor would support the weight without any problems, although I'm not sure where you'd find a used one.

[LarryG]

quote:Originally posted by Tundra_Man

My guess is that one of these fully loaded units weighs in the 800-1000 lbs range, which for a 2x2 footprint is a whale of a load. Now imagine a whole row of these lined up...

All right, I stand corrected. In 34+ years in architecture I've only worked on two or three projects that had any kind of accessible floor system, and none of them would have supported that kind of weight.

The main "lead" I've heard for finding an old computer room floor involves bank buyouts ... big bank buys out smaller bank, computers are consolidated in a regional operations center, smaller bank no longer needs all the hardware it had when it was independent. Or the same scenario except with hospitals. Either way, a clear case of needing to be in just the right place at just the right time.

[lrogers]

Again, I thank you guys. Good Ideas, good discussion. Now, I just have to put it into action.