Even with the best foundation, if your shed is located on soft, muddy ground or you have a lot of rainwater pooling around it, your shed could start sinking. Another problem is water wash.
Some places seem to be natural paths for heavy rains to travel. If your shed is located in one of these wash paths, the water will eventually erode the soil around the shed, causing sinking.
Obviously, the way to keep your shed from sinking is to give careful thought to its placement. Choose a level, solid spot for the shed. Pick more than one possible place to install it. Note the conditions of the soil in those places in both wet and dry conditions.
If possible, spot places that rainwater tends to travel and avoid those. These are usually easy to spot, due to leaves piled up on the sides and end or grass bent down with the water flow. If you already have a shed that is sinking or tilting, you’ll need to raise it and make the base underneath level again or build new supports to level it. For more information on preparing the spot for your new shed read my article How To Prepare The Ground For a Storage Shed.
How Do You Raise a Sunken Shed?
Your first step would be to find out if your shed is small enough for you to raise. You can ask the lumber supplier or call the support number for the manufacturer if you bought a pre-built shed. Be prepared to tell them what size the shed is and what siding and foundation it has.
While using jacks is the most common method, it can be done without them. First of all, take everything out of the shed. This is not just to minimize weight but to keep items from falling off shelves when the shed tilts. Use lumber to nail cross braces across window and door frames to prevent broken window glass and twisted hinges.
Bracing the studs is a good idea also. You can move your shed if it is small and you have a relatively straight path for it to travel. You can raise it with a lever or rope and slide blocks or rollers underneath. If moving the shed, one person takes the roller the shed just rolled off and puts it ahead of the shed.
If your shed is on a concrete slab, your safest course of action is to raise the shed off the slab and build a higher platform for it. You can level it by adjusting the height of the legs or props on one side. While a concrete slab can be lifted if it was reinforced, it’s very hard to do without cracking the concrete.
If you’re determined to try it, dig around the slab and use a lever to carefully lift one side at a time, raising it on blocks. Keep adding blocks until it is raised 10 inches, then fill the void with gravel and level it. Be advised that it will really be tough to add and spread gravel under the slab. When lowering the slab, take out blocks in a circle, one at a time.
It would be a good idea to place the shed on a framework of treated lumber or plastic foundation squares to keep it higher. Your slab will get wet, but hopefully, your shed won’t. For more information read my article How to Lift a Sunken Shed Foundation?
How Do You Lift a Shed to Level It?
Using jacks is the easiest way to do this. Hydraulic jacks or moving jacks are good choices. You’ll also need jack stands if you don’t have more than one jack. Again, take everything out of the shed first. Put the jack under a joist and jack up one corner a bit higher than you want it to be and place a jack stand underneath it.
Your other corner should already be lifted, but if it’s not high enough jack it up and place another jack stand underneath. Repeat this with the other side of the shed. You can read my article How to Build Your Shed Floor on Skids for a solid base for your shed that you can move.
Can You Use a Car Jack to Lift a Shed?
You can use a car jack to lift a shed, depending on its size. The weight of the building materials used will also have an impact. A shed with vinyl siding will weigh less and be easier to lift than a shed built with barn wood siding.
It would be better to start off with a heavier jack than to find out your car jack won’t handle the load and you’ll have to get a heavier jack anyway. You may be able to rent one.
How to Stop Shed from Sinking Again?
One way is to relocate the shed. While you may not want to do that if it sits on a concrete slab, it’s a lot easier to just abandon the old slab and pour a new one than to try to raise the slab and level it. If your shed is sinking from water or runoff problems, those problems are bound to keep happening in the same place and you may find yourself having to move it later anyway.
If your problem is caused by water, building a drainage system should be considered. You’ll still have to level your shed for now, but the drainage system will solve future problems. You’ll need to dig a trench eight inches wide by eight inches deep from the side of the shed with problems toward the place you want to steer the water.
The tricky part will be sloping the bottom of the trench at about one foot per 100 feet of trench. Put in stakes every 10 feet alongside the trench. Tie string to the first and second posts. Measure the distance from the string to the trench bottom. Tie the other end to the second post an inch lower and so on. This will help you slope the trench bottom.
Pour two inches of gravel into the trench and smooth out, keeping the slope. You’ll need four-inch perforated drain tile to fill the length of your trench. Landscaping fabric wrapped around the tile will keep dirt from clogging it.
Attach a PVC pipe with a 90-degree elbow to the top of the pipe and cap it. Part of this pipe needs to stay above ground to enable you to clean the drainage pipe without digging. Fill the trench with gravel until it’s about three inches below ground, then fill in with soil.
Hopefully, you’ll never have these problems with your shed, but if you do, they need to be dealt with. Sinking or tilting can strain the building materials and fasteners, not to mention windows and doors. Make your plans and get a few friends to help.