Concrete floor for workshop questions

[Wingnut]

Jim,
up here in mid-Michigan ... all pours have to have a "rat wall" ... which was specified as a 24" footer around the perimeter. I found this out when I had a pad poured for my 24 x 32 shop. Raises the cost ... but adds to stability and keeps the critters out from underneath.
For the implements, I'm just putting up a shelter with posts, and rail ties for keeping the implements up and off the ground. I think my wife would really freak if I put up (another) building and used it for implement storage (for some reason she thinks two 2-car garages, a shop and a barn are enough)

too bad that common sense ain't

 

[JimBinMI]

Wingnut,

Wouldn't the "rat wall" requirement be from your township, city or county? I go to my township office to get a permit, they tell me if my plan is OK or not. My pole barn has treated 2"x8" all the way around the outside base now and I plan on putting another one below it, so I will have a wood "rat wall" of about 16". I also like your idea of more concrete around the perimeter. One guy gave me the idea of pouring cement around the outside perimeter too, extending 1'-2' out, he'd seen it done before and gave it a nice finished look and was easy to mow around. Don't think I'll do that.

JimBinMI

We boys and our toys!

 

[Wingnut]

Jim,
I couldn't argue the requirement onee way or another ... the inspector was talking to my wife .. so whether she got it correct or not .. well, let's just say she's from Texas .. heh heh. She says he told her it was a Michigan requirement ... but heck, it could be township or county ... I didn't argue as I knew it would add strength and also keep the critters from digging under. I was more worried about the doggone moles than rats anyway!
Fortunately, the guy who put in the pad (I was on a business trip .. as usual) was also used to adding a block perimeter wall so I've got an extra foot of headroom ... always a good idea in a shop.
I had, in Alberta, a pad larger than the 3-bay garage. Reason I don't like that is ... it rains!. If the edges are flush water doesn't get into the garage ... if it ain't flush ... well, you know how it rains here in Michigan!

too bad that common sense ain't

 

[JimBinMI]

Wingnut,

I can definitely relate to moles! In my yard, and already burrowing tunnels around the barn! /w3tcompact/icons/mad.gif

JimBinMI

We boys and our toys!

 

[W5FL]

Wingnut,

No one asked that question, but it is a very important one.

Normally the details of the slab include a notch all the way around made by imbedding a 2x4 at the edge of the form. This gives a notch, that all water that runs down metal panels hits the bottom of the notch and goes outside rather than in the shop.

The same is true for the door and particularly for an overhead door. It MUST have a 2x12 or similar notch maker where the overhead door comes down so that water that blows under the door will be stopped and shunted back outside at the edge of the door. If you don't do that you will have a very wet workshop or garage.

Don't forget to put anchor bolts in each side of all openings and every 4 ft to tie down the base angle or 2x4 used at the base of stick framed walls. Otherwise the first really high wind, your garage or shop may blow over and leave a perfectly funtions SLAB of concrete where it used to be. /w3tcompact/icons/smile.gif

 

[ejb]

Concrete floors ...revisited!

OK folks, after all the helpful advice I got last time from people here about putting in a concrete floor in my existing woodframe, cynderblock foundation workshop, I decided that based on the advice I got here I'd better get some advice from a couple of local contractors, familiar with the local codes and freeze points etc.

When I first thought I would do this, I pretty much decide that I was going to excavate a few inches of the dirt out of my shop, level it off, put in some re-bar or wire mesh and pour a 4-6 inch slab. Seemed pretty straight forward to me (once I decided against the "pit" anyway). When I asked for advice here, almost everyone said I would need to put in footers, piers etc underneath the floor to prevent it from moving/cracking in the when the ground freezes...that made sense to me to I guess.

But now that I talked to 2 local contractors, both of the recommended my approach more or less, no footers/piers, just pour a 4 inch slab on top of what is there, use some mesh or rebar etc.

Now I don't know who is right. I only want to pour this once...the house I am in I will probably be in for another 50 years god willing, so I don;t want to take any shortcuts, then again, if the locals say I don't need footers/piers, it sure makes the job easier?

Any feedback on this from anyone?

If I go just the slab route, and use rebar or wire mesh, should I put anything under the pour? (insultation, sand, gravel etc?).

In case you can't tell, I am trying hard to get out of putting in footers and piers down to the frost line...that will significantly increase the amount of work that needs to be done, and since it is inside an existing building, chances are I would have to dig those pier holes by hand.

(Also, shop has a heater in it, but is unheated most of the time if that factors in anyhow).

Thanks all AGAIN!

 

[Budinohio]

Re: Concrete floors ...revisited!

ejb, here in Ohio they stress you must have a good firm base under the slab ,in my area they recommend at least a 6" base. Myself, I went with stone screenings ( got a good price ) 6" deep, I rented a power tamper and after I leveled the stone I sprayed it with water so it would pack tighter. I used fiber reinforced concrete and no rebar or wire. Good luck, budinohio.

 

[RickM]

Re: Concrete floors ...revisited!

ejb,
If I was building a house over a new slab with plumbing and possibly ductwork in it then piers are not an option. However if I was just going to pour a 'garage floor' then I would excavate down to lay in a 2" bed of sand and then fill to grade with 4" of the fiber reinforced concrete. The local contractors should know what works in your area, (and the local codes), but get more than 2 estimates /w3tcompact/icons/smile.gif.

 

[TomG]

Re: Concrete floors ...revisited!

We're in an area where a safe well feed is 5' down. As far as I know, building 'slab-on-grade' is an established building technique here--at least for non-residential structures. The slabs just float on the frost. However, the slabs do have to be strong enough to take the stress resulting from potentially different levels of frost heave across the slab. If one side of a slab has better drainage, it won't heave as much. Gravel/sand beds don't eliminate all the heaving problems, and drainage may be as important as a good bed. Anyway, I think contractors have 'pro forma' designs for these types of applications.

We were looking at property that had a house and a restaurant/garage. Part of the restaurant/garage was slab on grade, and the building seemed to have some problems. We talked to an engineering consulting company to get an evaluation of the building. The guy said that we didn't really need to pay his PEng rates for that type work. The company employed a guy with lesser qualifications, but who could do an evaluation just as well. The only catch was that the company wouldn't accept liability for an implied recommendation. Fair enough, and the price was right. Something like that might increase your comfort level. At least you get a knowledgeable opinion from somebody who's not going to get the contracting work.

The major problem with the building was that failed roof runoff allowed water to puddle under part of the slab. A few winters without heat really broke up a lot of the building. The rest of the property is nice, but we ducked that deal.

 

[roysallis]

Re: Concrete floors ...revisited!

Soon I will be getting the land leveled for my pole barn. I plan to put a living area in it so I will have a concrete floor and will install some plumbing and a small septic tank. Any suggestions/advice on installing the plumbing before I have have the concrete poured? Also, is it best to pour the concrete and then build the barn or build the barn and then pour the concrete? I am about 50 miles south of Birmingham, Alabama so I do not have to worry too much about the frost problem.

 

[gerard]

Re: Concrete floors ...revisited!

I think you have enough info on concrete but I didn't understand the one person's negative comment re a vapor barrier. In upstate NY good contractors put plastic sheeting down beofre the concrete is poured, not as a vapor barrier after the concrete cured but to ****** the curing process and prevent the moisture from leaching out as the concrete cures. For normal concrete (there are special mixes this doesn't apply to) the longer it takes to cure the harder it cures. The stronget concrete can be poured under water totally and will cure just fine) this is most important if you pour under hot dry conditions. in that case you want to water the concrete as it cures. I know one guy who poured his basement, plugged the drain and flooded it for a week as it cured! I know they used plastic sheeting under the floors at the Anheuser-Bush plant up here and those floors were 12 inches thick. I have to assume they know what they're doing!

 

[MarkV]

Re: Concrete floors ...revisited!

Roysallis, With a pole barn floors are poured after the barn is up or the poles have been set. No reason for put the slab in before the building because all the bearing will be on the poles you set in the ground. When you say living area and plumbing, the permit process becomes a whole differnt game in most areas. For us a pole barn does not require a permit but for a septic you have to have the health departments ok and the building inspector wants things way differnt than barn construction. Might want to check things in your area. Never fun when an inspector having a bad day stops by./w3tcompact/icons/smile.gif

 

[W5FL]

Re: Concrete floors ...revisited!

Interesting to live in the rural area of Texas. Only wells and recently Septic Tanks require a permit. Only Septic Systems ever see an inspector. They don't care whether you live in it, wire it or plumb it. California has uniform building code everywhere, but is pretty lax in the outlying areas.

I really though only horses, cows, and goats lived in pole barns, though. Prefab steel barns are almost as cheap, you pour the foundation first and insulate pretty well. Good barn for living quarters, but lousy for horses, cows, and goats, though.

 

[roysallis]

Re: Concrete floors ...revisited!

My barn will not be used for any kind of animals. It will be used for my tractor and other equipment. I do not live on the property now but plan to build a house in the near future. My plan is to sell my house and live in the barn while I am building my house. A perk test and field line plan is required by the health department before I can put in a septic tank, even though the barn is not considered a living unit.

 

[TomG]

Re: Concrete floors ...revisited!

I don't think of myself as a knowledgeable builder, but I think that plumbing, electrical etc. is pretty much done in exterior walls after the slab is poured. Except in commercial buildings that often have utility troughs build into slab floors, there's no room to work under on in an on-grade slab.

It's probably easiest to plan the living space so utility connections can utilize exterior walls (with enough insulation on the outside of pipes to prevent freezing). Of course, the electrical can be run through the roof space and down interior walls. Plumbing through interior walls isn't so easy. It's a good idea for drainpipe to have drainage angles, and running drain through interior wall studs doesn't seem like a great idea. I have run drainpipe on the outside of walls, but it doesn't look great.

In terms of living space and permits: In Ontario, an occupancy permit is required for any principal residence. Building and health permits are required before an occupancy permit is issued. Recreational spaces do not require occupancy permits, and the codes are less stringent for recreational occupancy (usually defined as occupied less than 6 months a year). However, we still had to get a building and health permit to set up a construction trailer at our camp.

The codes were changed several years ago, and now the required septic system for the trailer is a full residential system (very expensive). As an alternative, we're using a composting toilet. However, we still were required to build a raised 6' x 12' x 3' gray water leeching pit.

 

[Anonymous Poster]

I have a 40' x 64' foot pole barn, and had a slab poured last year. The 40' width with is broken down as 8', then a 12' sliding door, then the remaining 20'. I had the 8' and the 20' sections done, starting with a 4" base of pea gravel,a vapor barrier, used fiber concrete AND wire mesh poured 6" thick. The 12' width of the door was left dirt, from the front of the barn, all the way to the back. After everything cured, I added more dirt, so it came up to within 2" of the concrete floor. Filled that up with #57 limestone. The reason I did not have that section done, was that I have a 977 Cat, that weighs in the neighborhood of 44,000 pounds. If I ever get rid of the Cat, the last job will be to excavate that 12' section, and have it poured. I would NOT go only 4" if you have any heavy equipment.