Wednesday, October 18, 2017



Storage Shed Site prep. – Crushed Stone Base

A firm, level base is important to the longevity of your storage shed. In our storage shed buyers guide we discuss site preparation but I am going to go a little more in depth here.

If you don’t feel you can tackle the site preparation you can opt to hire a local landscape contractor.

Crushed Stone Base

The crushed stone base is now the most widely accepted site preparation for sheds under 400 square feet. For over 18 years we have been recommending this type of site preparation and within the past 2 years more and more towns and municipalities have begun to catch on and recommend this type of base to those applying for shed permits.

What you’ll need(for do it yourselfers)

  • Roll of string
  • Tape measure
  • Spade shovel
  • Wheelbarrow
  • Grading rake or iron rake
  • Line level
  • 4 stakes
  • Eight foot long 2″x4″
  • Four foot level
  • Crushed stone (amount based on size of shed – chart below)
  • Optional – Landscape fabric/weed cloth

stonecalculator

Step 1

Add 2 feet to the length of the shed as well as the width.

Next measure the area and place a stake in each corner. Remember to add the 2 feet to the length and width.

To be sure that your layout is square measure diagonally from corner to corner and be sure these distances are equal.

Square your area
Square your area

Step 2

First you must determine how deep you would like your base. I recommend at least 4 inches. With that said,starting at the highest corner wrap the string around the bottom of the stake and run it to the lowest stake. Place a line level on the string and pull the string taut. Move the string up and down until the string is level. Wrap the string around the stake at this height. At the lowest point measure from the string to the ground and add 4″ to this distance. Since this is the lowest area of the site this is where you will be excavating the least digging down only 4 inches. At the highest point of the site you will be digging down until you have excavated enough to create a flat surface to receive the stone.

 

Excavated storage shed site
Remove the grass and top soil

Step 3

Once the grass and topsoil are removed rake out the area.

Site prep excavation
Rake out the site

Step 4

Back fill the area with the crushed stone then rake it out so it is level. use the 2″x4″ to check for level. Be sure to check it from front to back as well as side to side. Check for level in several different spots as you rake out the crushed stone.


Completed stone site prep.

Completed stone site prep.

 

Step 5

This is an optional step but watering the stone can help it to compact a little better. The water will wash the finer particles through the stone allowing the crushed rock to settle.

Crushed Stone Base w/Timber frame

What you’ll Need

  • Circular saw, chain saw or cutoff saw
  • Timbers – I recommend 6″ x 6″ timbers however 4″ x 6″ will work as well. Make sure they are ground contact rated pressure treated. The timbers must be equal to the sum of the four sides of your site. For instance if you are creating a elevated stone pad for a 10′x16′ shed you would first add 2′ to the length and width then add the four sides together. So you would need 60 linear feet of timber (12 +12 + 18 + 18 = 60).
  • Depending on how high you will be building your base you will need additional timbers to be used as “dead men”.
  • #5 Rebar or similar cut to 4′ lengths. You will need 1 piece of rebar for every 4 feet of your frame.
  • Drill (hammer drill recommended) and a 5/8″ drill bit which can reach a depth of 6″ minimum
  • Sledge hammer
  • Roll of string
  • Tape measure
  • Spade shovel
  • Wheelbarrow
  • Grading rake or iron rake
  • Line level
  • 4 stakes
  • Eight foot long 2″x4″
  • Four foot level
  • Crushed stone (to calculate the amount needed use this chart)

Step 1

Follow steps 1-3 used for the “Crushed Stone base”

Step 2

Place the landscape timbers around the perimeter of the site. Be sure the timbers are level. Drill holes through the timbers every 4 feet and rebar the timbers into place using the 4′ lengths of rebar. For larger bases you may want to add “dead men” which are timbers which run perpendicular to the outer timbers to help keep the from moving however since the outer timbers are set in the ground the dead men are not entirely necessary.

Step 3

With the timbers in place you can now backfill your site with the crushed stone.

Stone base with Timbers
Stone base with Timbers

Comments

14 Responses to “Storage Shed Site prep. – Crushed Stone Base”
  1. Don says:

    Wow what timing ! I’m glad I found this site!
    Thank You!

    I am planning on putting in a 10×12 shed soon.
    I was wondering what type & size of “Crushed Stone” to use?

    I want it firm enough to resist shifting but NOT so firm that water tends to linger around.

    I was thinking about stone like Railroad balast stone
    http://www.bowesconstruction.com/Images/Rock/20.jpg

    Or maybe a combo of it and a Road-Pack type mix where main runners would sit (if it has them)?

  2. admin says:

    Don,
    That stone looks perfect as long as it is not larger than inch and a quarter.
    I wouldnt worry about using hard-pack or screenings where the runners are sitting. The crushed stone will compact well enough to support the building while still allowing for drainage.

    Good luck with your project!

    I’m uploading some older posts and a section for people to share pictures of their sheds. Stop back and add yours when you finish.

    John

  3. Don says:

    Thanks John and will do.

  4. John says:

    Thanks for info. I have some fairly large tree roots (around 4″ or so)on my soon-to-be shed site. Do I have to remove them or could I cover with stone. Thanks.

  5. admin says:

    Is the tree still there?

    If the tree is still there I would try not to disturb them. Assuming they are a few inches down then I would just stone over them. Eventually, they may push the stone and therefore the shed up causing it to be out of level so keep that in mind.

    If the tree is dead I would cut the roots at the edge of the site and yank them out. Over time they are going to deteriorate and cause the stone and shed to settle and fall out of level.

    Hope this helps

  6. jon b says:

    Is there a way to use the stone method as a foundation with large roots very near the surface?

  7. admin says:

    Hi Jon sorry for the late reply.

    If you read the reply to the previous question above it may give you the answer.

    Ideally, you do not want to remove the roots unless the tree is dead.
    If the tree is not dead then you run the risk of having the roots knock the shed out of level over time.
    You could also dig around the roots the best you can and back fill with the crushed stone however you will still have some leveling issues in the future.

    I would suggest stoning on top of the roots and then setting the shed on some 2 or 4 inch thick solid concrete blocks.

    Good luck and let me know if you have any other questions.

  8. Doug says:

    Thanks for the advice. I’m considering a portable garage at this point for my storage needs. I’ve never owned one before. I’ve heard that some of them may have cheap covers, however, if not purchased from the dept stores they should be of good quality.

  9. ML says:

    So, I’m not real clear on proper drainage. Seems like if you dig a 3 inch hole and fill it with rock, you have a 3 inch deep pool full of rocks, whereas without the hole the water could run down a slope and away from the building. How’s the water get away?

  10. admin says:

    @ML

    The stone base does more than offer drainage.
    When you get backsplash around the shed from rainwater running off the roof the stone which extends around the perimeter keeps the run off from splashing dirt back onto the side. Further, it keeps weeds and grass from growing around the shed which will cause the siding to deteriorate over time.

    Pooling water could be an issue if you get several inches of rain or if the site is in a low lying area but having done thousands of sites using the crushed stone base method I have yet to experience a problem.

    Also you should go 4-6 inches deep not 3″.
    Hope this helps.

  11. Dave says:

    1. Should landscape cloth (the type that is placed under mulch) be under the gravel to inhibit the growth of weeds around the shed?

    2. Please reinterate the size range of the gravel that should be used under the shed.

  12. Russell says:

    With the crushed stone base is there any need for runners or will it be ok to just start your floor joists on top of the crushed stone once leveled up?

  13. admin says:

    Russell –
    Still use the 4×4’s under the joists. This allows the floor to breathe whereas putting the joists directly on the stone will limit airflow.

    When using the grid floor system you can go smaller on the joists (2×4’s) as long as you go a little smaller on the centers (12″ O.C)

    Depending on the width of the storage shed here is what I recommend:

    8′ Wide = (2) 4×4’s running the length of the shed with floor joists running the width 12″ O.C.

    10′ Wide = (4-5) 4×4’s and 12″ O.C. 2×4’s

    12’wide (Same as 10′ wide)

    14′ (5-6) 4’x4’s and 12″ O.C. 2×4’s

    Be sure the joists and runners are PT and are ground contact rated. .40 would be your best option.

    Good luck hope this helps.

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