In this article, I will try to cover all the necessary steps you need to make to build a shed base on uneven ground.
Either your shed is prebuilt or you will make your structure using shed plans, the work is the same.
The ground must be leveled!
The options available are two:
- Level the ground itself.
- Construct a leveled deck above the slope.
To decide which option suits you the best depends on a few factors you have to consider.
Table of Contents
Factors to Consider
1) How big is the slope of the ground?
If the ground is too steep try to find a new location to suit your shed. In case you have no alternative don’t worry. There are solutions for everything but the impact on time, work, and money is considerable.
2) The condition of the uneven ground
What is the type of soil?
Clay? Rocky? Solid Clay?
Is it possible to dig the ground with hand tools without damaging your back?
Does it contain big heavy rocks difficult to level or remove?
Can you level the uneven ground by yourself using simple hand tools or is an earthmoving machine necessary?
Is the ground steady enough?
Depending on the weight of the shed, if the answer is yes, then it’s ok. If not, then a few additional simple actions need to be taken to fix the issue. It is essential for building a shed base on uneven ground to have or make the ground super steady.
Are there any tree roots you have to deal with?
It depends on the size, but generally speaking, it is difficult to cut and remove tree roots from the area you want to transform. If you insist, an earthmoving machine can do it easily. Is there an option to find another place to build your shed? A big tree is going to be near your shed. Do you want this? Bad windy weather can break a tree branch and land it on the roof of your shed. And that is a good scenario. The bad scenario has a collapsed roof or a shed in pieces played on the ground. Think about it.
Is it getting swampy?
Avoid this kind of ground at any cost. You don’t want your shed to be exposed to conditions difficult to confront. Mad, moisture, mold, and mildew impact your shed structure and your belongings stored inside, in a catastrophic way. In addition, the lifespan of your shed will be shortened.
Not to mention how difficult it is to make any kind of shed base on such a ground. Especially on uneven ground with these attributes. To say this in other words it is completely inappropriate to build a shed base on this type of ground.
Also, accessibility issues will occur if you manage to complete the structure. The mud from time to time will make your shed inaccessible for vehicles or even yourself on foot.
Drainage
Inspect the selected uneven area for water flows. During heavy rainy days observe the groundwater flow. Make sure the selected area isn’t in a water path. If your shed becomes an obstacle to water flows it will not last for long. Nothing stops water from its natural path. You will end up seeing the shed being removed by the water flow during a rainy day.
In addition, water embracing the shed from time to time will cause other problems that have to do with moisture affection and maintenance difficulties.
Sun exposure
Is there plenty of sunlight around your shed? Complete shadow conditions lead to mold unless the moisture is very low which is a rare situation. Depends on the usage of the store. If you want to store wine, for example, shadow conditions are perfect. If it is going to be a tool storage shed, sunshine conditions are preferred. Choose what suits your needs.
The usage of the shed
The things you plan to store in the shed will determine their weight and consequently the method you are going to follow to level the uneven ground.
Access to water and electricity
In case you want water in your shed be sure the selected place doesn’t forbid access to the water supply.
When it comes to electric supply, we have the same considerations. There is also an efficient alternative as an eco-friendly solution with the usage of a small photovoltaic unit. If the sunlight is efficient and you need to supply only light balls with electricity, you are ok.
Is your shed going to be accessible from all sides?
This is important for maintenance issues. Your shed needs maintenance from time to time, so you want to be able to have access to all around the structure.
Zoning requirements
The type and size of the construction you plan to build must be compliant with Zoning Requirements and local laws. Before anything, make the appropriate arrangements with the authorities and then proceed with all the rest.
Now let’s proceed to the available solutions:
1) Level the uneven ground itself
Low gradient
If the slope has a very low gradient and is smooth enough with up to middle-sized rocks or roots, you have the option to level the ground by using simple garden hand tools.
Start digging with a hoe to remove the soil from the high to the low area of the ground. It requires a little sweat equity. With this tool, you can remove rocks and cut small roots easily while digging and pulling the soil towards the low side. Make sure you haven’t left any peaks of soil or rocks excessing the ground. Sometimes use a shovel if you find it more convenient.
When you think the ground is leveled enough then it’s ok.
It doesn’t have to be accurate. The rake will perfect the leveling.
Remember that accuracy isn’t a necessity at this stage.
Now the ground isn’t compact enough especially at the side you relayed the soil dug from the other side. So press the ground somehow to make it as compact as you can. Heavy machinery, a car, or even your feet can help.
An unusual way of doing this is by splashing water with a hose on the ground to get wet enough. After the water evaporates, the soil will be denser.
Compact soil on the ground helps to achieve a steadier base and prevents any roots from invading, due to the lack of water.
Ok! The ground is leveled, it has become compact enough, and you are ready to start building the shed base. In this case, the slope was low, remember? So there is no need to build a retaining wall.
That being said the rest stages of the structure are the same as building a shed base on an already leveled ground.
High gradient
Again: the best option is to pick another position for your shed.
But with no alternatives, follow step A1 with the only difference being to use earthmoving machinery to level the uneven ground.
2) Build a retaining wall
To prevent the soil from collapsing suddenly one day and burying your shed with all the stored stuff, you want to build a retaining wall to hold back the ground.
Dig a ditch to lay the first row of bricks inside. The reason for that is you want the foundation of the wall under the ground. Build the retaining wall and there you go.
Now proceed to build the main structure which is the shed base.
Build the shed base
At this stage of the process, you want to build the shed base on the ground that you have already leveled, and there are several options available:
- Build a concrete slab using a timber plank frame. Ideal solution if your shed is without a floor.
- Build a gravel pad in a box made of pressure-treated lumber. It is the best option in case your shed has a floor.
- Use concrete blocks to place a timber base above them.
1) Build a concrete slab base
Benefits of a concrete shed base:
- Durability
- Easy to clean
- No affection by moisture and rot
- Can be set very close to the ground so there is no need for a ramp.
Should the concrete slab be the same size as the shed base?
The answer is definitely yes! The surface of such a slab is smooth and the water bumps on and splashes all around. With this option, there will be fewer water splashes on the sides of the shed. Thus the shed is protected In the long run against rot and mold.
Make a timber plank frame
First, decide on the thickness of the slab. It depends on the size and weight of the shed, as also the climate of your area and the local building codes.
A 4-inch thickness suits most cases especially if reinforced with steel. You can park cars and store workshop equipment in the shed without problems.
Get 4 pieces of 4-inch x 2-inch timber and assemble a rectangular frame with the same perimeter as the perimeter of the shed.
Note that the inside measurements of your frame are the size you want your base to be.
In the end, you are going to remove it so do not overdo it with the 4 joints. Simple big nails to join the sides are ok.
Level and secure the frame
Now with the frame ready to be used, you can place it directly on the spot you have already leveled.
If you find that the ground isn’t stable enough and prone to erode, dig it out at a depth of half a spade and lay gravel as a subbase. Level it, place the wooden frame, level the frame again, and make it firm.
Make sure the frame is completely rectangular by measuring with a measuring tape the 2 diagonals of the frame. You want them equal.
Take your time to level and then secure the frame to achieve stability. For this, you need a bubble level and piles. Make sure the piles do not protrude the top of the frame so as afterward not to prevent the leveling procedure.
Calculate the volume of the concrete
Width x Length x Height = Volume in cubic meters ( m or cubic inches
The volume of the concrete needed depends on the size and the usage of your shed.
A 4-inch thickness is adequate for most common garden sheds. On rare occasions, it can be up to 8-inches. This is the HEIght of the concrete base. The Length and the Width are the dimensions of the area formed by the wooden frame.
Example
Let’s say we want to calculate the volume of a 10 x 8 concrete slab with a thickness of 4 inches.
Length: 10 feet = 3,33 yards ( 1 foot = 0,3333 yards , 10 x 0,3333 = 33,3 yards)
Width: 8 feet = 2,64 yards ( 8 x 0,33 = 2,64 yards)
Height: 4 inch= 0,11 yards ( 1 inch = 0,08333 feet, 4 x 0,0833 x 0,333 = 0,11 yards)
L x W x H = 3,33 x 2,64 x 0,11 = 0,97 cubic yards or 27 cubic feet ( 1 cubic yard = 27 cubic feet)
That makes approximately 1 cubic yard, and for this, you need 3600 lb or 1625 Kgr of dry concrete.
Mix the concrete
A concrete mixer, a wheelbarrow, a shovel, and a plastic bucket to add water are the necessary tools to make and carry wet concrete.
At this link you will find a concrete calculator:
https://www.concretenetwork.com/concrete/howmuch/calculator.htm
There are 2 options:
Ready-mixed concrete
All ingredients are included except water. The number of bags you need depends on the weight of the bag.
An 80 lb ready mixed concrete bag covers 0,6 cubic feet. So consider using about 45 bags for a 10 x 10 slab with a thickness of 4 inches.
For the volume of water needed read the instructions on the bag.
Make the concrete by mixing cement, sand, gravel, and water
This option requires more work, but it is much cheaper. For the dry materials, the standard ratio is 1 part of cement, 2 parts of sand, and 3 parts of gravel.
The ideal amount of water is the one that makes the mixture a nice workable paste. It’s about ½ of the volume of cement you put in the concrete mixer.
In our example which is 1 cubic yard of cured concrete, we need
7 bags of 94lb of Portland Cement
1350 pounds or 13 cubic feet of Sand
2100 pounds or 21 cubic feet of Gravel
Useful Tips on How to use the concrete mixer effectively
Let’s admit that a concrete mixer is the best choice for a better and quick result with less fatigue.
- Locate the mixer and the ingredients near the worksite. Bring an empty barrel nearby and a hose connected to a water tap. Use the hose to fill the barrel with water and get yourself a bucket. With this, you can count the portions of water needed for the mixture in the mixer.
- Make sure the concrete mixer is laid on even ground. Avoid unstable surfaces.
- Apply a tiny thin coat of diesel to the inside of the drum. This will prevent the mixture from sticking to the interior surface of the drum. Be careful not to overdo the fuel because it will affect the mixture’s quality.
- Get the inside of the drum a little wet with the hose, and start adding the gravel or sand first.. Keep the ratio of 3 or 4 parts of gravel to 2 parts of sand for one part of cement. You can count the parts using the shovel.
Keep the ratio of the materials
For example, put 6 shovels of sand and then 9 or 10 shovels of gravel for 3 shovels of cement. Use the bucket instead of the shovel to fill the drum if you want. The ratio is the same.
- For every bucket of cement add ¾ bucket of water.
- Inside the spinning drum with the mixture of gravel and sand, add some of the water to make it wet. Then add the cement. Let it spin for a while and add the rest of the water a bit at a time until the mixture becomes workable.
- Ideally, add only the amount of water necessary for the mixture to become workable.
After a few minutes, the concrete mixture will be ready for transportation. Use a wheelbarrow to carry and pour the mixture inside the frame. You may need to fill and carry the wheelbarrow two or three times until the drum gets empty. As you keep adding concrete in the frame, keep leveling it with timber until the frame gets full.
The whole process of laying the concrete requires at least two persons. One for making and carrying the mixture and one for layering and leveling the concrete in the frame.
It is a nonstop process until you end up filling the frame.
When you finish, don’t forget to clean up the cement mixer. Use the water hose for this. Add some gravel with water to the drum and leave it spinning for a few minutes for better results. As long as the concrete is still wet you can remove it easily.
Generally, clean all your tools after using them with water. There is no need for chemicals.
Now that you have the slab ready and leveled in the form of a wet concrete mixture, make sure to keep it wet as it cures. Splash water on the slab with a hose from time to time for several days if you can. This will guarantee an excellent result in the quality of the concrete.
2) Build a gravel pad
Building a gravel pad as a base for your shed is without a doubt one of the best choices, especially if the shed you are going to install on it has its own floor. Keep in mind that the surface of the gravel must be larger than the surface of your shed due to better draining results.
I propose to keep a 2’ distance from every side of the shed. Thus for a 10’ x 8’ shed, you need to build a frame with the inside dimensions of 12’ x 10’.
Benefits of building a gravel pad for your shed base
- Protection: It is the number one choice for protecting the structure of your shed. This is because the gravel helps drainage in a very efficient way. Thus you don’t have to worry much about rot or mold affecting the floor joists and the runners under the shed.
- It provides perfect weight distribution along the floor. Much better than concrete piers, or shed foundation blocks that support the shed on specific points. This benefit becomes a necessity when it comes to heavyweights such as vehicles or other machinery being stored in the shed.
- It is a simple and easy to build and install, structure.
- Cheap.
- Less labor than the other solutions.
Mark the corners of the gravel shed pad
Carry some stakes and a string line or a marking paint and go to mark the perimeter of the wooden frame of the pad. Make sure to mark at the outside edge of the perimeter, to dig later for the lumber to fit on the ground, without losing the marked lines.
Now as you have marked the 4 corners, use a tape measure to make sure the 2 diagonals of the marked area are equal. With this method, you keep the frame rectangular. You will need to repeat this process after you lay the first course of lumber, but if you keep some accuracy from the beginning, at the end you will achieve a rectangular frame quite easily.
I highly recommend the door of the shed be as close as possible to the ground level. So there are 3 possible places for the door. One is on the downhill side and the other is on the uphill side of the ground we have already cut away to make it even.
If you want the door to be on the downhill side, then you want to build up with lumber in the excavated area to protect the back of the shed from the soil sides of the ground.
For the door on the uphill side, you want to build up the downhill side with lumber to make it level.
Sometimes if the slope is too steep, a combination of the two above methods can fix the problem. Building up one side and digging out the other while using the extra soil for a small ramp at the door side is an acceptable choice.
Lay the first course of lumber
Pressure-treated lumber 4”x 4” or 4”x 6” rated GC which stands for “ground contact”, is the suitable wood for the frame of the gravel pad. For a level ground, one course of lumber along the perimeter would be enough. Since the ground is uneven, you will need more lumber depending on the size of the shed and the gradient of the slope.
With the extra lumber, you will build up the downhill side or you will cover up the excavated site of the ground as a retaining wall.
You need to dig a ditch
Start digging a ditch along the marked line at the lowest side of the site. Dig away 2” to 4” of topsoil and make it wide enough for the lumber to fit. Lay the first piece of lumber and adjust it to be completely level. Then proceed to the next one until you lay the whole perimeter with the first course of lumber, or until the lumber stays below the ground level. Check again if it is level using a sticking level at least 48” long.
As soon as there is a layer of lumber around the perimeter, measure the two diagonals of the frame. You want them to be equal, remember? Now that the first course of lumber is level and the shape rectangular, join the pieces of lumber at the corners or next to each other permanently, using a drill and 4” exterior screws.
As you continue, fasten each layer of lumber with the course below, with 2 screws every 2’ or 3’. This will prevent the frame from shifting in addition to the rebar stakes you will use to fasten every two or three courses together. When you lay one or two courses use a drill and ½” auger bit to drill holes through the perimeter every 6’-8’.
With a sledgehammer pound 2’ stakes through the holes into the ground. Follow the same procedure every 3 courses of lumber. A 24” rebar for the first two courses is enough. For the upper layers, use 16” rebar stakes. The point is to secure the first one or two layers with the ground, and the rest layers if any, with the below layers so that the frame is firm and stable.
Bracing
Depending on the height of the walls you may have to enhance the stability of the structure with bracing. Especially with slope conditions, where probably at least one side of the frame will be build-up or down more than 20”, you need to apply bracing.
This technique is about adding pieces of lumber randomly perpendicular to the wall.
For a build-up wall, the additional lumber should be pointing inwards at the frame. Hence, when the gravel is added the bracing will tie up the whole pad preventing the gravel from shifting the wall outwards.
If the wall is below the ground as a retaining wall, add the extra lumber in a way that extends outside the pad. When you add the excavated soil to fill the gap behind the wall, the bracing will prevent the inside curving of the wall as time goes on.
Do you need to add a perforated drainage pipe?
Well in the case of the gravel shed foundation there is no need to add drainage pipes. The water will sufficiently flow to the ground through the gravel.
In the rare situation where the slope has a significant gradient and there is an uphill at the rear side of the shed, a perforated drainage pipe will protect your shed by channeling the water around the perimeter.
Now that you have finished the wooden frame, remove any extra soil hills from the inside area. Make sure every spot is at least 4” lower than the top lumber, leaving room for the gravel to fill the space. The extra soil can be used in the outside area to even the gap between the lawn and the edges of the pad, especially at the door side.
Tamp the soil
You are almost done! Just tamp any excavated soil properly inside the pad to prevent the shed from sinking. For this use any heavy equipment available. A mini skid steer or a tamper can be very helpful.
Add a weed barrier to the gravel shed pad foundation
Order more fabric than the bottom surface of the foundation, since you’ll fold it up at the edges and secure it at the perimeter lumber with a staple gun tacker.
With the woven stabilization fabric with a class 3 rating the gravel will stay clean from weeds. This choice of fabric is strong enough as it is designed for road construction.
Fill the pad with gravel
Without a doubt, the most important material for the gravel shed pad is the correct type of gravel. When I say “gravel” I mean crushed stone. Gravel is rounded pieces of river stone, which aren’t appropriate in our case because they can’t be compacted properly. Thus your shed won’t be supported enough and it will end up shifting after its installation.
The best way to form a firmed and compacted base is to use “clean crushed stone”. Other order names of the material are “ ¾” clean “ or “ ¾ “ washed or #57.
You already know how to calculate the volume of the gravel, so it’s time to fill the lumber frame with crushed stone. For this, you can either use a dump truck from the store you ordered the gravel, or a wheelbarrow and a shovel to complete the filling process.
Your frame is already leveled, so leveling the gravel surface is very easy. The leveled lumber can be used as a guide for you to drive a screed board on it while pulling the gravel and finally leveling it. A 2×4 or 2×6 straight piece of timber wood is suitable for being used as a screed board.
Tamp the gravel
Are you ready for the final step before enjoying the results of your efforts? I’m sure you want a perfect result so you won’t skip this part. If you want a firmed and locked foundation for your shed, you have to tamp the gravel.
A hand tamper can do the job, but if a gas-powered vibrating plate is available or you can afford to rent a vibratory plate compactor, it will save you time and labor while achieving a perfect result.
Be careful and follow a pattern while tumping the gravel. For example, a circular spiral pattern from the edges to an inwards direction will keep the gravel evenly packed. Avoid tumping going forth and back cause the gravel will end up being gathered on one side.
Congratulations!
Your gravel shed pad foundation built on uneven ground is now ready. Be ready to start installing your shed!
As a final thought, building a shed base on uneven ground is a situation you want to avoid. In case there is no alternative you have a variety of solutions to choose from.
In this post, I have covered in detail some of them and I would be glad if reading this will make you decide what works for you best.
If you have any questions or proposals or objections about anything do not hesitate to leave a comment below or to contact me.