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Discussion Starter #1
Folks,

I have a large 80 x 80 asphalt pad in my back yard on which I would like to construct a wood frame shop, maybe 24 X 24. I am not real good with the terminology but here goes. The asphalt is not perfectly level so my thought is to frame in a level foundation "mold" and have concrete poured in directly on top of the asphalt. I guess I would have to put some rebar in there for strength. The real question is will this work? Will the Concrete last? My guess is that the ashpalt is about 6 inches thick after years of repaving. I would like to pull a car in there to work on, what thickness would allow this?.

Any thoughts on this? Thanks.

Rich
 

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The Magnificent
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In the peoples' republic of MD you would probably be hauled out and shot in the public square.

Seriously, check with the county building office. Their advice is already paid for by your tax dollars and as they will be the ones signing off on your permit, I would value their advice over all others.

Not to denigrate the advice of a lot of members who are professional contractors, or homeowners who have been there and done that, but they will not be signing off on your permit.

I spent about two hours with my building department and came away with a lot of valuable information.
 

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asphalt is used as a base under concrete roadways a lot. So in terms of if the asphalt-concrete combination will work it will be fine. I would recommend a 6" to 8" thick slab using 6"x6" WWF (welded wire fabric).

As D-dogg suggest check for your local building requirements.
 

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Discussion Starter #4
they will be the ones signing off on your permit, I would value their advice over all others.
The People's Republic has forced me underground. I would still like to hear from the masses.
 

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I might be worried about water getting between the concrete and asphalt, freezing and heaving. If there is good drainage under the asphalt, you might consider punching holes through it in the low spots.

I'd also consider coating the asphalt with a latex bonding agent and adding latex to the concrete. If the asphalt is well weathered, there should be decent bonding.
 

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Ditto on D-Dogg's thoughts. All depends on the local officials.

I had to chop up portions of a 4" CONCRETE PAD, and pour true footers at the corners. And they wanted to inspect before I poured to verify the depth.

Where I live, any shed larger than 8'x10' requries footers!!! ugh
 

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Up here you must have a foundation on any structure over 100 sq.feet..
They would not let me use a "floating slab" on my quonset garage,despite the fact many HOMES were constructed nearby using them back in the 70's..(maybe they turned out to be trouble,I dont know)..

I ended up digging 3' down and pouring footers and walls,just like a house would have,only my building needed it 10" wide ,not 8",and 10x20" footings..(for a building that weighs all of 3500 lbs!)..
They said I could use asphalt instead of poured concrete IN the building for a floor,but I didn't see any practicality in that,seeing it would be more costly than concrete,and have several disadvantages..!

I bet if your town wanted to put up a building on a paved parking lot,it would go right up--but if YOU want to do it,you'll need at the least,a variance,permits,lawyers,etc,if they will even consider allowing it to be done....I think sometimes "building codes" is just another name for "extortion money",myself..
 

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I Love All Color Tractors
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I would not use the asphalt as a base for your concrete. It is not below the frost line.

I would excavate down to at least the frost line, probably 24" and pour footings at least 12" thick and 24" wide. For footings reinforcment, use three #4, or 1/2" rebar running parallel to the direction of the footing 6" on center leaving 3" on each side to the side of the footing. Make sure the rebar have at least 2" of clear cover between the bars and the bottom of the footing. When bars have to be spliced, overlap them no less than 12" and provide a piece of rebar 18" long running across the three bottom bars every six feet to tie them together.

Bring the walls up with concrete block to 12" above grade.

For the floor, use 4 to 6 inches of crushed stone under the pad. Place a vapor barrier on top of the stone and then pour at least a 4" slab using a grid of #4 rebar, 12" on center in both directions.

This will give you a nice garage. Of course other opinions will vary, and I am sure that many will say that this is overkill. But hey, everyone has an opinion.

Like most others have said, consult your local code office. If you don't want to talk to them, ask a local engineer and I am sure that they will probably agree with my design.
 

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Since you apparently are going with out a permit, I'm wondering why not just have fresh asphalt laid to level the portion you are gonna use? In my neck of the woods, concrete is pretty expensive. And what kind of life do you want from the building? 20 years? 100 years? If 20 to 25 years, I'd lay the sills of the walls right on the asphalt using treated lumber. Anchor it securely using the expanding fastener of your choice. Will it be to code? Heck no! Will it hold together for 20 to 25 years? yep.
 

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I would go with post #8 and do it right... haven't you seen what happens to the roads during freezing and thawing, do you want your garage to look like that? And putting it directly onto the asphalt... how would you keep water from going under the walls?
 

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In the peoples' republic of MD you would probably be hauled out and shot in the public square.

Seriously, check with the county building office. Their advice is already paid for by your tax dollars and as they will be the ones signing off on your permit, I would value their advice over all others.

Not to denigrate the advice of a lot of members who are professional contractors, or homeowners who have been there and done that, but they will not be signing off on your permit.

I spent about two hours with my building department and came away with a lot of valuable information.
The above quote is very good advice as all locations seem to have different examples of what to do. You are really better off pulling a permit as in most places they have a tendency of catching people who do not.
 

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Discussion Starter #12
You all offer valid advice and I greatly appreciate it, and I really mean that, it is why I asked. I work for the local Gov't and I see everyday how they must adhere to the rules, it's what I do too but for reasons other than building. I undestand that the rules protect the general masses, however; the rules are sometimes out of line with what is reasonable. I just want a workshop; actually I want a MANCAVE, I don't want to live in it. I am not an engineer but my asphalt driveway was originally laid in 1947 and it has not heaved from freeze yet. I think it is a decent foundation.

I like the idea of some sort of a barrier that will keep moisture from infiltrating the asphalt/concrete interface with a polymer added. Adding more asphalt to level it out also has merit.

Permitting in this jurisdiction is an absolute PITA, but I will take some of your advice and covertly talk to the guys at County to see what they say. It can't hurt. Thanks gentlemen.
 

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:Stop: As a contractor and architect I am going to tell you that it will not work.
You are in cold country and you will not have any foundation. You need to go down below the frost line for you state and area you are in. It will will not work, Repeate after me it will not work. Rent a backhoe and saw. Cut out the spot where you want the shop. dig it up with a back hoe and make sure it has propper footings. The size you want your shop is a full size garage. You will have junk if you build it that way. You will add great value to your property if you do it right. You are going to pour a slab and the only extra will be the foundation and footings. You can form it with plywood and use the plywood for sheeting the roof. If it worth spending that kind of money do it right. :00000060: :00000060: :00000060: Pour your slab at least 6 inches thick for a shop. Machinery can crack up a floor. :fing20:
Good Charlie Brown. :duh:
 

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What about a traditional pole barn construction? Pressure treated posts placed to a depth below the frost line. 4 posts per bearing side, 12 - 24' long common trusses, a couple more posts to fill in the gable sides and frame the door. Simple, inexpensive, and a couple of guys with tractors can pretty much get it closed in a weekend. Unless you are working on something extremely heavy, just leave the asphalt as the floor.

Here in NY they would burn me at the stake if I built it without a permit, but this would meet our codes here.

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Discussion Starter #15
Points well taken guys. I am going to take a step back and re-think this.
 

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The Magnificent
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Wish I had a picture of a restaurant in South Boston, VA, which was built on the ground using timbers for a foundation. Probably built before the UBC, but to see this thing makes you hesitant to sit in it long enough to eat.
 

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I'm liking the pole barn idea. Just cut out the asphalt where you need to bore holes for the poles. Then you have solid footing and a asphalt floor.
 

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Discussion Starter #18
I'm liking the pole barn idea. Just cut out the asphalt where you need to bore holes for the poles. Then you have solid footing and a asphalt floor.
Todd

This idea is looking good to me too. What would you think I could use to keep rain water from getting in under the walls? Don't know if you've seen the sea of ashpalt I have back there but it does generate a lot of runoff. I don't know if there is some type of membrane that would make it watertight.

Rich
 

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Todd

This idea is looking good to me too. What would you think I could use to keep rain water from getting in under the walls? Don't know if you've seen the sea of ashpalt I have back there but it does generate a lot of runoff. I don't know if there is some type of membrane that would make it watertight.

Rich
It's been a really long time since I was to your house, so I don't remember.
I'm sure you could figure something out to seal the bottom. It would not be structural, so you have a bunch of options.
 

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I don't see why it can't be done.....since I have done the same thing LOL

My preferred way to build post frame shops are on a floating slab, but if that isn't allowed then punch the holes for the post through the asphalt and build a traditional post frame.

Then pour a 6" minimum concrete floor. I prefer rerod but mesh will work if that is what you prefer.

If water is an issue from the up hill side you could have a swale made out of asphalt to force the water around the building.

You can PM me with any question if you want.
 
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