DIY Rain Shelter for the Garden: Open Lean-To with a Fiberglass Roof
A dug-out style shelter with a roof that slopes from front to back, three walls and an open front. The lower walls are reclaimed pallet boards; the upper walls are canvas panels that clip on and off, so the shelter can be opened up for air or closed against wind and rain.
The finished rain shelter with picnic tables underneath. Photo: OathAbiding913, CC BY-SA 4.0, via Appropedia (resized)
The story behind this build
A student farm in a rainy, windy part of northern California needed a covered place to work, store supplies and hold small classes. A previous shelter there had struggled with the wind, and the team designed this one, nicknamed the Water-Den, with that in mind.
It holds 10 to 15 people, has hooks to keep gear off the ground and shelving along the walls. The canvas upper walls can be unclipped on the rare sunny days or removed completely before storms, so the wind cannot use them as sails.
How it is designed
Footprint 12 × 8 ft, with a post in each corner set 2 ft deep in concrete.
Front posts are 4×4×12 and back posts 4×4×10, all pressure-treated, so the roof slopes toward the back.
Stringers and rafters carry a fiberglass roof.
Half walls of reclaimed pallet boards on three sides, set into shallow trenches, with a rail on top.
Upper walls of canvas, hemmed and fitted with grommets, clipped to eye bolts with carabiners.
The front stays open between the two tall posts.
Materials they used
Two pressure-treated 4×4×12 posts and two 4×4×10 posts
Concrete for the post holes
Lumber for stringers, rafters and railing
Fiberglass roofing panels and roofing screws
Reclaimed pallets for the half walls
Joist hangers, hooks and eye bolts
Canvas: one piece 12 × 5 ft and two pieces 8 ft long, 5 ft high at one end and 7 ft at the other
Grommets and carabiners
How they built it
1Prepare the area
Measure out a 12 × 8 ft rectangle and mark the corners. Clear the area and dig a hole 2 ft deep at each corner, lining the holes up with each other.
2Set the posts
Stand the two 4×4×10 posts in the back holes and set them in concrete, with teammates holding them level. Repeat with the 4×4×12 posts at the front.
3Build the roof
Measure the roof slope and trim the posts to height. Attach the stringers, then the rafters with supports, and screw the fiberglass roof into place.
4Build the pallet walls
Dig shallow trenches along the two short sides and the back. Pull the loose nails from the pallet boards, stand them in the trenches and nail a rail along the top, fixing it with joist hangers. Leave the front open.
5Add hooks and eye bolts
Screw three hooks into each short side for hanging tools, and eye bolts into the frame for the canvas.
6Make the canvas walls
Cut the three canvas pieces with 3 extra inches all round, fold the edges twice to make a 1½ in hem and sew it. Put six grommets along each long side.
7Clip on the canvas
Fit a carabiner in each grommet and clip it to the eye bolts. The panels can be unclipped for air or removed before strong wind.
More photos
Fitting the rafters for the sloping roof. Photo: OathAbiding913, CC BY-SA 4.0, via Appropedia (resized)The frame with roof and the first pallet walls. Photo: OathAbiding913, CC BY-SA 4.0, via Appropedia (resized)The four posts set in concrete. Photo: OathAbiding913, CC BY-SA 4.0, via Appropedia (resized)
Use and upkeep, from the builders
Pick up litter in and around the shelter daily.
Repair the canvas as soon as damage is noticed.
Replace the canvas about every five years, and re-stain or oil the wood at the same time.
Our notes if you build one
How deep posts must go depends on your soil, frost depth and local rules; 2 ft worked for this site in a mild climate.
A roofed structure of this size may need permission in some places. Check before you dig.
Take the canvas down before storms, as the builders recommend: fabric walls catch a lot of wind.
Credits and license: Built and documented by OathAbiding913, Daniel Richards, Isabelle Carroll and Ruben Janssen, engineering students at Cal Poly Humboldt. Originally published on Appropedia: “CASA Student Farm rain structure” under CC BY-SA 4.0. This page is our summary of their documentation and is shared under the same license (CC BY-SA 4.0); photos are credited individually. Measurements and costs are the builders' own and refer to their site and year. DIY Outdoor Builds did not build this project.
Building work can be dangerous and may need a permit. Check local rules and use a qualified professional for electrical, gas and structural work.
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