Can I put gravel against a wood fence?

November 14, 2020 7:46 PM

I’m building an outdoor sauna in the corner of my yard and it needs to sit on 6”-8" of gravel. Rather than dig, I was hoping to just put the gravel on top of the dirt and tamp it down, but this means the bottom 6" of my unpainted wood fence will be touching that gravel. If that is a bad idea, is there another solution that would allow me to put down the gravel without having to dig and still not compromise my fence?
posted by Dragonness to Home & Garden (7 answers total)

Put a pressure treated 2x8 between the fence and the gravel spaced from the fence 3/4" or so.

You probably want to constrain the gravel anyways and building a 2x8 PT frame around the gravel area would be effective. You can dig down just the width of the 2x8 to make it level with your gravel.
posted by Mitheral at 7:52 PM on November 14, 2020 [1 favorite]

What you need to prevent is moisture being held against the fence palings for longer than it needs to be after a rain. If you have 8" of gravel piled up against the palings, the bottom few inches are going to be permanently damp, fungi will move in and colonize the wood, and the fence will rot from the bottom up until enough of the wood has been eaten away that moisture no longer gets held against what's left.

Tidiest way I can think of to deal with this is to get in ahead of the fungi. If you cut off the bottom 8" of your fence and replace it with a horizontal PT 2x8 (or, better, a concrete retainer) that doesn't quite touch the remaining palings, what you end up with at the bottom of the fence is a neat cut edge instead of a raggedy rotten one.

Next tidiest would be to step your retainer a few inches inside the fence, so you end up with a nicely ventilated trough between palings and retainer. But this will eventually fill up with blown-in leaves and rot the fence anyway.
posted by flabdablet at 9:37 PM on November 14, 2020 [2 favorites]

This is what "gravel boards" are for. That's the UK term (you might describe them differently in the US) for solid-material horizontal boards, typically concrete, about six inches to a foot high. The wooden fence panels sit on top, high enough above the ground to be in no danger of direct contact.
posted by vincebowdren at 2:53 AM on November 15, 2020

Echoing flabdablet: if the bottom of the fence is in contact with dirt or gravel, in 12 to 18 months you'll have warped boards on your fence, due to uneven drying after rain. Always leave a gap between the bottom of the panels and the top of the ground underneath. Even 1/2" can make all the difference.
posted by SPrintF at 8:39 AM on November 15, 2020

And the lord said, if you want a wooden structure to last, lift it above the earth so the life-giving rains and rot-giving moulds do not collect upon it.
So, yeah, what everyone else says. Either cut the wood short or restrain the gravel.
Or sadness will come unto thee.
posted by seanmpuckett at 9:45 AM on November 15, 2020

Gravel against the fence is no good. But, also, you want a stable footing for the sauna, which an unconstrained pile of gravel may not provide over time as the gravel shifts because the edges of the pile are free. If you plan to have this set-up for awhile, I’d construct a short wall on all sides to hold the gravel in.
posted by quince at 5:15 PM on November 15, 2020

Response by poster: I’m so glad I asked! I’m just building a retaining wall on one side of that rectangle and have lots of extra blocks left, so I’ll use them to create edging for the sauna base.
posted by Dragonness at 7:18 PM on November 15, 2020 [1 favorite]