Will asphalt support for a wood shed storing firewood?

civilian · Nov 1, 2022

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 · Nov 2, 2022

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 · Nov 2, 2022

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 · Nov 2, 2022

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.