We started building a shed in our garden. Now we would like to close the sides using wooden planks. To keep the wood in a good state as long as possible we want to leave a gap between the lowest plank and the ground, but don't want water to run into the shed. How could we close that gap? Any ideas what material would be best to use?
We thought about trying to build a concrete lip all the way around but this would be difficult for us and we aren't sure if it's the best way.
I’d install 2x4’s horizontally at about 24” on center to the exterior side of the posts. (The bottom horizontal 2x4 should be pressure treated.) Then I’d install a cheap wall sheathing (if required for seismic active area or high wind area.)
If not required, then install a moisture barrier directly to the 2x4’s. The reason we install a moisture barrier is because we know the siding will leak. Wind and rain will “push” moisture into the wall system and cause dryrot.
Then I’d install the siding (the boards you described) vertically letting them span from horizontal 2x4 to horizontal 2x4. I’d make sure the boards lap the bottom horizontal 2x4 by about 1”. This will give a “drip” so water can’t “wick” back up into the wall.
Summary:
Installing horizontal 2x4’s allows a moisture barrier to be installed to protect the existing posts, etc. The posts are not pressure treated (no incising) but may be decay resistant if it’s cedar or redwood, but they will eventually rot. For added protection, you can add a metal strip (called “Z-flashing “) to the very bottom of the wall to protect the end grain of each vertical board from water and pests.
I see no reason you could not use treated lumber, it appears to me to be the simplest solution. It would probably blend better than any other type of material.
I encountered a similar problem when I built a greenhouse about fives years ago. I framed walls that housed reclaimed windows. The walls were built overtop of cinder blocks and it left a gap about the size of the cinder block all the way around the greenhouse.
My building aesthetics manager (wife) insisted that it be "pretty". I ended up using corrugated galvanized metal, which was pretty cost effective. I cut the metal to size using circular saw with a metal cutting blade (at the time, it was the best tool I had for the job).
I buried dirt up to the corrugated metal inside and outside to provide some extra insulation. The metal has held up surprisingly well, above the soil surface it still looks new and under the soil there is little rust in some locations.
Here you can see the gap under the windowed wall.
Here you can barely see the metal skirt around the greenhouse. And the leftover metal was used for the raised beds in the background.
