Putting concrete floor & drainage in pole building-Need help.

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I want to put a concrete floor in a 24'x40' corner of a pole building for a shop area and have some questions. Am I right in putting a footer on all four sides (even though I may later expand the floored area) Should I extend rebar out through the two interior sides of the slab to tie concrete floor areas more solidly to this one?

The other concern I have is drainage. Center drain (or centered drains) or a grated trough drain(s) and where? More importantly, to where or what do I drain? I have no septic in at this time. Do I need one for this? I don't want to run the risk of spilling something (gas, oil, paint thinner, whatever) and having it end up contaminating my groundwater as I may build a home there and will need a well. What can I do to have a working shop area and drainage therefrom without danger of groundwater contamination?

Any other suggestions you might have regarding this pole barn upgrade project are more than welcome, too. ;o)

-- Gary in Indiana (gk6854@aol.com), October 17, 2001


Hey Gary, sounds like a fun project. Can't see that it would hurt to put footers all the way around. If you ever did want to support something on those interior edges you'd be set. I'd definitely leave rebar exposed to tie in future floors to this one, as long as the rebar won't be a trip hazard...are you backfilling the interior to slab height?

About the drainage, I'd do a center drain and pipe it to a graywater pit. Say 4'X4'X4' hole (or so, I always end up making mine smaller for convenience of digging) filled with washed stone and covered with landscape fabric and then covered with 4 or 5" of dirt. Unless you plan to be dumping just tons of toxics down this drain I don't think the occasional little spill would foul your groundwater. Come to think of it, the drain could be close to an outside edge of your slab; less digging and piping.

How big is the entire barn?

Have fun! gilly.

-- gilly (wayoutfarm@skybest.com), October 17, 2001.

footers would depend on any future use. The drain,,, does the ars flood now? if not,, your goning to raise the grade there, so it should after you pour. If it does flood now,, then I would dig a trench around the slab,, put in, "drain tiles" new pvc perforated flex pipe works,, backfill with some gravel, should be fine. DOnt attach to your septic,, you dont need it for drainage. You could also slope the edge up,, to form a depression in the middle of the slap, so if you did spill something nasty,, it couldnt flow onto the ground and would give you time to clean it up

-- stan (sopal@net-port.com), October 18, 2001.

The barn is 70' wide and 80' deep. It's divided with a truss height of 12' on a 40' x 80 open section and 9' on the 30' x 80' section that was used for horse stalls and a tack room. I'd like to pour a floor in the front 24' of the 40' wide area. There are two 12' x 12' doors on the front of that area so I'd have plenty of access.

The area behind it has two 10' x 10' doors on the side with some windows at the rear. I thought about putting some gravel in there so I could drive on it and use it for vehicle and equipment storage. I at least want to put some stone over the exposed rebar ends for safety.

The 30' x 80' section has a 10' wide concrete drive running from 10' x 10' doors front and rear with 10' deep stalls on either side. I have no idea what I might eventually do with that area. Again, I'm open to ideas. ;o)

-- Gary in Indiana (gk6854@aol.com), October 18, 2001.

I would not use any footer. Have a good base to pour on. Drainage so soil under slab stays dry. Use welded wire mesh or no steel at all. If the soil below slab does not move the slab will not break. Get a good dry mix and cure it properly. If driving heavy vehicles on it go 5 inch thick. If you expand slab drill holes every foot and add rebar then. You could make a water oil separator out of 50 gal. plastic drum. Water flows out oil stays in. If you wash floors with soap, oil and water might mix allowing some oil into environment. Might have to pump separator out every 5 or 10 years.

-- ed (edfrhes@aol.com), October 18, 2001.

If you want a little extra strength along the edges of the slab, just make it thicker. Unless you are driving heavy equipment on the slab, you generally don't need reinforcing. I use old wire mesh fencing to reinforce slabs.

As for drains, it sounds like what you need is an oil/water separator (OWS). You can fabricate one yourself or spend some bucks on a unit at a concrete/pipe supply yard where the contractors and road builders shop. In their simplest form, an OWS can be nothing more than a concrete or plastic catch basin with a 90 degree downward facing elbow on the outfall pipe. Run your floor drains into the catch basin. When the basin fills with water, gas and oil will float on top. The elbow, pointing down, is submerged and the gas/oil is prevented from flowing out. Only the (relatively clean) water will flow out the elbow. The basin should be cast as a single unit so there are no seams for water to seep out from and the pipes should be well grouted to seal up the cracks. There should be about two feet of storage below the pipes. You will need to periodically clean sediment from the bottom and skim the oily gunk off the top for proper disposal. For extra treatment, run your outfall pipe into a grass lined swale. Line the swale with a clay base soil to limit the rate of absorption and build it with a very slight slope and shallow sides. Make it at least 50 feet long. Plant grass in the swale. As the dirty water flows through the swale, it will be biologically filtered before it gets into the ground water. This is a standard water quality treatment method required by counties and cities for new development to treat storm water runoff from roads and parking lots. The fancy name for it is "Bio-Filtration". You can probably find construction details at your local county building department.

-- Skip in Western WA (sundaycreek@gnrac.net), October 18, 2001.

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