Your running out of storage in the house and garage and thinking about adding a storage shed outside, only problem is your yard has a fair amount of slope and not sure if building a storage shed is worth it.
It’s not advisable to build a shed on a slope. Depending on the type of foundation you use, building on a slope will put a strain on your foundation in places, and may even lead to problems.
Your shed foundation will be very important to prevent such problems as boards or studs slowly separating from their attachments, warping, window, and door frames not working properly, and others. Of course, depending on your yard you may have no choice but to build your shed on a slope if your whole yard has a slope. Even a slight slope must be accounted for and counteracted when building a shed.
Can You Build a Shed on a Slope?
It is possible to build a shed on a slope, but it’s not really advisable if there is another choice. You’ll have to do a lot more work to the foundation, and it may limit the types of foundation you can choose. You’ll also have to deal with rainwater flowing toward and around your shed and possible soil erosion.
Soil erosion can eventually lead to enough soil washing away that it causes your foundation to crack or otherwise lean or give way, leaving your shed tilting or even falling in certain circumstances.
If you choose to build a shed on a slope, be sure to check with local building codes. They may have specifications on how deep your foundation or support posts are installed. If you have to get a building permit for the shed you can explain your situation and find out what restrictions, if any, you will have to follow.
The Importance of Drainage on a Slope.
Even when you avoid situating your shed in a water flow track, water will flow down any slope if the rain is heavy enough. You can build a small wall a short distance from the high side of your slope to steer water away from the shed. It can have a slight curve or angle to get the water to flow to either side. The ends of the wall should extend past the sides of the shed to keep the water away.
A French drain will also help with this. Start by digging a trench around the uphill side of the shed. The trench should be eight inches deep, and eight to twelve inches wide. The wider the trench, the more water it can handle. Figure out if the uphill side of the shed is a little lower horizontally than the other. That will be the side you extend down the slope.
If the ground is even across the high side, you’ll need to build an artificial slope to keep the water flowing down the pipe. You can extend it along the drip line on the sides of the shed to catch runoff from the roof if you don’t have gutters or you can extend one end down the natural slope.
Smooth out the bottom of your trench, then line it with landscaping fabric to prevent plants from growing up through the trench and dirt from entering the drain pipe, clogging it. Cut the fabric wide enough to go up the sides and wrap back over the top later. Another method is to wrap the fabric around the actual drain pipe before laying it into the trench.
Lay two inches of gravel along the trench bottom, smoothing it out flat. Place 4-inch perforated PVC pipe into the center bottom of the trench with the holes at the top. Check it with a level to make sure you have a slope to encourage water flow.
Fill the trench with gravel, leaving two inches of space at the top if using the landscape fabric to line the whole trench. This is where you wrap the remaining fabric over the top of the gravel, overlapping the cloth in the middle. Fill the rest with more gravel even with the surface of the ground around the trench. For more information on dealing with water drainage read my article What’s The Best Way to Add Drainage Around a Shed?
What is the Best Way to Level the Ground for a Shed?
Measure and mark the area for your foundation with stakes at the corners. Tie string to join the stakes together. Clear out any vegetation and rocks from the area. Then dig out all the topsoil if possible. This is needed because topsoil is usually softer than the soil underneath and could potentially shift under the weight of the shed and its contents. Typically, topsoil will be a different color than the harder subsoil underneath, so look for a change in color.
To even out the space, lay a plank across the ground. This will show you any slight peaks and valleys that can either be filled or shaved off as needed. If your excavation is deeper than you need, spread some of the topsoil back, raking the soil to break up any lumps.
Tamp down the soil, going over the area as many times as needed until the soil stops being compressed when tamps. Use your plank over the soil again with a level to make sure the whole space is level. Depending on the kind of foundation you plan for your shed you may want to install a landscape fabric to block the growth of weeds to finish out the dig. If you need some help or ideas on how to deal with the ground issues read my article How To Prepare The Ground For a Storage Shed.
Things to Look at Before Building on Sloped Ground
You need to look at how steep the ground is. Also, note whether the space is in a spot where water naturally drains or runs when there is a lot of rain. A shed should never be placed in a spot that is a natural track for water runoff. The soil will erode around it, eventually eroding enough to affect your shed’s stability and structure. Take a little time, if necessary, to notice where water naturally flows in your yard. It usually follows certain paths every time there is heavy rain.
Also, you need to examine the type of ground in your chosen space. Do you have exposed rock? Does your soil have a lot of clay which might make digging for a foundation or post holes difficult? If you plan to store heavy items, such as bags of cement, or you plan to store heavy equipment such as a riding mower or welding equipment, you may need to go to a gravel foundation or a concrete pad.
Figuring out the placement of the door or doors is another consideration. If you have anything wheeled to store in the shed or plan to use it for heavy items that are hard to carry, you need to put your door on the side of the shed that will face the top side of the slope.
Otherwise, you’ll need to build a ramp, and this will be much easier to build on the lower side of the slope. You’ll be faced with counteracting the slope with the ramp building if you place the door on a sloping side.
Is it Worth it to Build on Really Sloped Ground?
It’s a lot more work and usually more expense to build a shed on a steeper slope. You will probably need some type of retaining wall or use the method of posts attached to concrete poured into holes dug into the ground on the low side. You are limited as to the foundation you can use.
Most people who build on this type of slope find that they can use the extra space underneath the shed on the propped-up side for storage. Panels can be put around your posts as an enclosure if you plan for storage. On a steeper slope, the shed door will have to be put on the higher side of the slope.
What Foundation Types are Best for Sloped Ground?
If your slope is not very steep, your best course of action is to level the ground for the foundation. This will allow you to choose from the same foundations as with any other shed. If your ground is too steep for this, you’re limited to using posts attached to concrete forms sunk into post holes or building a retaining wall of concrete blocks.
For the side on the high side of the slope, you can use pier or deck blocks. Pier blocks are made of concrete with brackets attached to attach your horizontal beam. Deck blocks are also made of concrete but have a slot into which you insert the beam. You then build a deck platform attached to the beam or posts and wall to build your shed upon. Check out my article What’s The Best Shed Foundation Option For You? for the different types of shed foundation options that you can use.
How to Build Shed Foundation on Slight Slope?
The best way is to dig out the foundation to level the ground. You might want to dig out a space larger on all four sides to accommodate extra gravel to allow for drainage around the shed. Start out by using stakes to mark out your foundation. Put stakes on all four corners, then tie strings to connect the stakes. Tie one string to every pair of stakes and make sure the string shape is level. This way you can adjust just one or two strings if the shape is not level.
You can use single solid concrete blocks to help even out the ground if you don’t or can’t dig the base into a level state.. Use one tier on the high side, and build up a higher stack of two or three blocks on the low side to even out the side. Measure the height of your blocks and use that to help you figure out how far to dig.
For instance, if the difference in soil height is six inches and the blocks are four inches tall, you’ll need to stack two blocks for your lower wall, but you’ll also have to dig out the foundation hole lower on that side to even out the difference so that the tops of the blocks are even and level.
How to Build Shed Foundation on Steep Slope?
It would be a good idea to use the pier and post construction method, even after leveling out the space to keep your shed above draining water. It only takes a heavy downpour to wash debris up against the shed or for the water level to rise to the bottom of the shed joists while it’s pouring. A shed should never act like a dam for water to build up behind it.
Many people who build on a steeper slope build the shed right into the slope. This involves measuring out the placement of the shed, then digging straight down and across to form an L-shaped excavation for your shed. The bottom of the excavation should be level. You’ll also need to allow extra length at the vertical side of the excavation to build a retaining wall.
Leave some space between the retaining wall and the shed so that you can access that side of the shed for maintenance and to check on the condition of the wall. You also don’t want the shed wall to be so close that rain will splash from the top of the wall and onto your shed wall, keeping it damp.
You may be tempted to use the dirt you’re digging out to build up the height of the horizontal base and make your vertical dig more shallow. This would not be a good idea, however, as you would have to make sure that the soil you add is tamped down completely. If you build up the soil higher than the actual ground slope, you’ll need to build a second retaining wall on the low end to keep the added soil from washing down.
Contacting your building authority is vital in this situation. Building codes may restrict the height of the shed above ground or the height of the retaining wall. If your retaining wall needs to be over three feet tall, you probably need to contact a builder or engineer to check out the ground stability and the feasibility of building the wall you need. For more information on permits read my article Do You Require a Building Permit For a Storage Shed?
Building a shed on a slope is definitely a challenge, but once you get the foundation problem settled and constructed, the rest of the project should go along just like a shed built on level ground. With a little extra planning, you’ll be able to end up with a usable shed.