Will asphalt support for a wood shed storing firewood?

[plowhog]

I want to build a shed to store firewood and garden tools/supplies.

Dimensions are 11ft wide by 6ft deep. 8 foot front wall, 6.5 foot rear wall, single slope roof. Half will be devoted for firewood storage-- I estimate about a cord and a half of hardwood such as oak. So I have the weight of the shed, plus firewood, to consider.

My ideal location has a 3" layer of asphalt, with about 4" of well compacted road base beneath that. Is that sufficiently strong so I could just lay 4x6 pressure treated lumber on top of it, then build up? Or should I remove it for a different method? I know oak firewood is on the heavy side, so I'm not sure what sort of weight support to expect from asphalt.

 

[ljjhouser]

Probably be ok but depends on how hot it is in the summer there. Is asphalt easy to put down or would concrete go down easier. I have no idea how to asphalt an area.

 

[seville009]

I want to build a shed to store firewood and garden tools/supplies.

Dimensions are 11ft wide by 6ft deep. 8 foot front wall, 6.5 foot rear wall, single slope roof. Half will be devoted for firewood storage-- I estimate about a cord and a half of hardwood such as oak. So I have the weight of the shed, plus firewood, to consider.

My ideal location has a 3" layer of asphalt, with about 4" of well compacted road base beneath that. Is that sufficiently strong so I could just lay 4x6 pressure treated lumber on top of it, then build up? Or should I remove it for a different method? I know oak firewood is on the heavy side, so I'm not sure what sort of weight support to expect from asphalt.

I wouldn’t hesitate to do it; shouldn’t have any problems based on how you describe it.

If the asphalt is been there awhile, that is probably better (more hardened and settled) than if it was relatively new.

If it does settle after awhile, you can just drag it to another spot.

 

[Hayloft]

Probably be ok but depends on how hot it is in the summer there. Is asphalt easy to put down or would concrete go down easier. I have no idea how to asphalt an area.

I vote to build it on the asphalt. Ballpark shed weight should be around that of a fully loaded pickup and cars and passenger trucks sit on 3" asphalt all the time. But like already mentioned if your temps get real high it's possible to get some asphalt sag (or imprint of your shed footprint) over time. Mitigate that by spreading the shed weight out with a larger footprint like more 4x6's or something --- just enough to spread the weight out.
Another solution might be to cutout small squares thru asphalt enough to use ready made pier blocks and set your 4x6's on them. That way your shed won't sit on the asphalt.
Good luck/regards

 

[stumblinhorse]

Interesting topic, I cannot do asphalt for less $ than I can do concrete in a small area. I have an 12’x16’ area I would like to do the floor of in my barn. The price is about the same. And concrete is much cheaper when I do it myself which I cannot do asphalt myself.

 

[seville009]

I read his post that the asphalt is already there, not that he wants to put new asphalt down. Maybe I’m misunderstanding…….

 

[stumblinhorse]

I read his post that the asphalt is already there, not that he wants to put new asphalt down. Maybe I’m misunderstanding…….

Ah, I get that now.

Sorry, carry on!

 

[plowhog]

Ballpark shed weight should be around that of a fully loaded pickup .... Mitigate that by spreading the shed weight out with a larger footprint like more 4x6's

My pickup is +/- 7,000 lbs without a load, spread over 4 wheels. Didn't think about that comparison.

Extra "cross bracing" under the flooring to better distribute the weight is a very good idea.

 

[dodge man]

Very long term it might shift, settle some but it’s just a shed so I wouldn’t worry about it.

 

[ljjhouser]

I read his post that the asphalt is already there, not that he wants to put new asphalt down. Maybe I’m misunderstanding…….

Wow....Missed that. HAS I thought is said ideal solution is. Thank you.
Then, in retrospect, if there, I would use it as is and see what happens. Best Wishes.

 

[civilian]

Are you building walls and a roof? Or a floor over the asphalt? The firewood on the existing asphalt would not be a problem in my mind. Even with hot temperatures, the roof should cool it some. If it is entirely enclosed with 4 walls, how will the firewood dry out? Just some comments. Jon

 

[Tntcwg3]

Asphalt has almost zero strength on it's own unless you have temps below the softening point of the tar composition, high temperatures diminish what little it does have. The surface integrity is based on the base material beneath it. I use reclaimed (milled) asphalt on my driveway and here under the Texas sun it will often melt together resembling a solid topping. Large chunks seperated out and left unsupported will break apart and collapse under their on weight. Concrete is probably the better option in the long run.

 

[LD1]

Cord and a half of oak...~6k lbs....shed, and other junk....maybe 4k.

So not more than 10k and way more contact with the asphalt than a truck or truck and trailer.

If your that worrked about it, throw down a couple more 4x6 runners to double the contact area. Should be some cheap insurance.

I know when it comes to dirt in regards to posts and footers, good clay mix is supposed to support ~3000 pounds per square foot.
Id imagine asphalt with a good base under it would be double that.....

So as long as you have more than a couple square ft of contact area, you should be fine. And on a 4x6 post....that amounts to about 4'.

Or think of it the other way, .....if you run the 4x6's the short direction of the building at 6', 2 of them should give you about 6 sq ft for 10k lbs

Thats 1600psf, or about 12 pounds per square inch of ground pressure. Take a 1" x 1" steel bar that is 42" long and stand it on end on your driveway. Thats ~12 pounds of steel on a 1 square inch section of drive. Do you think it will settle?

 

[tshep]

I just did very similar - existing asphalt I wanted for a floor (to park tractor-loaded trailer). I leveled 4x6s on the bottom, recoated with copper-coat, and evened out with 2x4s above to get an even 'foundation'. Big overhang, careful site selection so roof water will drain away, not into wood. I also made anchors to spread out under the asphalt that secured the 4x6s. It will outlast my ownership.

HOWEVER, I spent so much time leveling those 4x6s that I could have cut trenches in the asphalt, dig down an extra inch or 2, sand filled bottom to set skinny concrete blocks, and leveled from there (same as 4x6s, shift every 1 1/2 inch difference). Having done it, the cutting and base adjustment would have been quicker.
I had to set the 4x6 in place, level it (with shims) over all end to end, then level side to side at each corner (more shims), transfer shim dimensions to opposite corners diagonally, then adjust all so it offset its neighbor by 1 1/2 - whew! Then I had to cut these slanted lines, often with an angle at the saw table for side to side.

The cut, sand, block method would have been much smarter and more permanent. Don't walk or work too near the cut edge (asphalt NEEDS side support), and after placing tightly fitted blocks, fill any gaps with sand for that side support.

 

[shooterdon]

Funny how I do not think things through. I would have built the shed without any second thought.