I need to make a pressure-treated wooden walkway set into soil that is 90% sand; I’d like it 4′ wide, at ground level and able to take (once) the 1000# weight of a big tool on a cart with pneumatic tires. The walk can be edged with low plants with dense root systems to stabilize the soil a bit. The ground can’t be made perfectly level, but is relatively flat. Rainfall is moderate, occasionally heavy. Anyone have any experience with a design that worked?
thanks, S Sittler
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So, this it like a beach boardwalk, I'm thinking?
That might be as simple as a pair of doubled ground-contact PT on-edge, with PT treads spanning across. The 2x "stringers" could be leveled, with 2x stakes to "anchor" them into firmer bearing soil deeper down.
This will sound over-simplified to some reading here--but I'm also thinking that this entire deal needs to be simple, as the direct ground contact will not give this project a huge long life. That means, simple is simpler to repair/maintain. Also, with a mostly sand soil--the soil conditions are likely to change, year-in, year-out--heaving here, dropping away, there. That does not suggest a real permanent structure.
Basically, either you build footings or you try to make the thing float. If you float it, you'll probably have to occasionally jack it up out of the sand, but the frequency with which that is required will vary depending on traffic and weather conditions.
Simplest would be prefab sections maybe 6-8' long (longer is more stable but harder to handle), "floating" on a pair of (or maybe 3) PT 2x6 laid flat, with deck boards layed across those. Some sort of cross bracing would be needed to keep the sections from racking, and where the sections meet you'd want to bolt or pin them together somehow.
When you set them some minimal cut/fill activity will likely be required to make them sit flat. If large amounts of fill (more than about 6") are needed then crushed limestone or some such would be better than sand or dirt. If you need more stiffness than the flat 2x6s give you (to bridge irregularities better), 2x4s or 2x6s can be set upright on the flat 2x6s and nailed or screwed every 8" or so, then the decking attached to that.
If you have the time I'd suggest prototyping a couple of designs out of scrap, to see what works out.
For footings someone would have to do the load calcs, based on knowledge of your specific conditions. But if you keep the deck light, and the traffic is also light (in terms of frequency of traverse) then likely something like a pair of 4x4s every 3-4 feet would work, with them resting on 6" or so of well-packed crushed limestone in a 6-8" diameter hole, at least 18" deep deep.
Code may or may not be an issue where you live. Here this would be regarded as a "patio" (deck lower than 18" high) and isn't subject to code. Other places the code covers tomato stakes.
Disclaimer: Have not actually built anything like this.
Thank you very much Dan for your thoughtful reply.
Freeze/thaw cycle an issue where you are?
If not, the Big Box stores sell spikes that are driven into the ground to accomodate 4 x 4s and even 6 x 6s. Use these to set posts wherever you see fit and attach the 2 x 6 rims.
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I would just lay ground contact 4x4 on the ground for joists at 16" oc, and then deck it over. stagger the joints.
The load is no problem. Look aty it this way - that thousand pounds is split amoung four tires so the immediate load is 250# in point contact. Ever worry about a 250# man walking on one foot at a time?
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