The best way to protect your garden shed from internal moisture is with a proper foundation. If moisture gets in, it will encourage the growth of unhealthy molds. These will damage your shed and you may have to tear it down. Follow these instructions to lay an effective garden shed foundation, and install windows and vents properly to keep out moisture.
How Does Moisture Get Into Your Garden Shed?
There are several points of entry for moisture to get into your garden shed. It can enter through the walls above ground, if they are not correctly finished. It can seep into the wood walls and frame if they are directly on the ground, or it can enter through vegetation that grows under and up the sides of garden shed walls.
Each of these problems requires a different solution.
Garden Shed Foundations
You can make the simplest garden shed foundation for a shed less than 100 square feet in area, from square patio stones. Dig a 2-inch deep foundation into the lawn, and compress the earth with a vibrating compactor. You can rent one from a building supplier or equipment rental service. Lay the stones and fit them tightly together. Fill between the stones to prevent plant life growing between them. Construct your shed atop the stones.
For a larger shed, pour a concrete foundation into a four inch deep mold made of 2x4 planks. Let it cure for one week, then seal it and build your shed on top.
To save the cost of a concrete foundation, consider a plastic shed foundation. These are made of grids that weigh about 2 kg (less than 5 pounds) each, of recycled plastic that would go to a landfill instead. Level the ground on which you will build your shed, and compress it to make it firm. Spread out a layer of landscape fabric to suppress weed growth underneath.
Place grid blocks to cover the area to the correct size. The grids measure 20 inches by 20 inches, and are 2 inches thick (50 cm x 50 cm x 5 cm). They interlock so you can build your foundation quickly. Cut grids with a handsaw to reduce them to the size you need. Fill each grid with fine pea gravel, and construct your shed on top. Lay a waterproof floor later on top of the grid frames if you choose.
Install Windows and Vents
Windows will allow light into your shed to save you the expense and trouble of electric wiring. Install them into precisely measured wall holes, and seal around them with high-quality weatherstripping, to keep out all kinds of precipitation. Add heat vents to your garden shed to let hot, humid air out and draw in cool air. Seal the edges of the vents with caulking or weatherstripping. If you live in a climate with lots of snow and wide temperature variations, choose vents with louvered shutters that you can close firmly in winter.