Site Prep for Large Shed Question

This thing is coming in a week, and I need to get ready.  Does anyone have experience with a shed sitting on two runners? I am assuming that as long as they are properly supported and level, I don't have to worry about supporting the outside edges.  Would you? 

My site is pretty level, so I am thinking about just laying some spare blocks that I already have on hand to support the runners.  The other option is to lay a pad of limestone, but why prep a 12 x 16 pad if the thing only sits on two 4 x 4 x 16s? 

Help! 

I don't have any good answers but I'd be thinking about drainage. When it rains, where does the water go?

Also an issue but maybe more of just an aggravation - put anything down for weed control? 

My shed sits on two runners like that.  Each one sits on concrete pavers (solid 16' square 2" thick cinderblocks)  Otherwise the spot is just bare dirt.  I suspect a raccoon hides under there sometimes but the dog chases it out.

A couple years ago my son backed into the shed and knocked it off the pads and i had to jack it up with the shop jack and drag it back into place with the suburban and a tow strap.

TLDR, cinderblocks are fine.  Get them level before they deliver the shed.

FWIW, the shed is at the edge of the woods and critters will live under it. (A 6' Blacksnake lived in the old shed.) I am not worried about that, my cat kills anything that moves. 

For drainage, it is at the edge of a hillside and the yard slopes towards it. I will probably have it high enough that any water will pass under it, but might trench something as a precaution. 

My biggest experience on sheds is the more ground moisture you keep away from the underside, the longer it will last.  The shed my father put in when I was little had a vapor barrier covered with gravel under it as well as regrading to redirect any water that might have flowed under it. 30 years later, I think that shed is still there and solid.

Apexcarver said:

My biggest experience on sheds is the more ground moisture you keep away from the underside, the longer it will last.  The shed my father put in when I was little had a vapor barrier covered with gravel under it as well as regrading to redirect any water that might have flowed under it. 30 years later, I think that shed is still there and solid.

This.

That shed doesn't look cheap. I'd invest in some fabric and a yard of Gravel. Create a little trough to divert the water  out from under before spreading the gravel.

Well worth the time and $.

I’d call the guy who is putting it in. I bought a pile of little 1 X 6 ish blocks per the installer’s request when we put ours in.

If you want it done “right,” pre-fab no-slab is probably not the way to go.

My $.02 YMMV

My buddy got one then parked a ffr cobra in if and it sagged beyond the runners.  They came back and put 2 more runners under it

We bought a 14’ by 30’ shed a few years ago. The company we bought it from also did the site prep. They came with a tri-axle dump with a bunch of stone in it. I forget what type of stone was the final layer, but I can take pictures. I stapled landscape fabric (stainless steel) around the bottom where critters could go underneath to keep them out.

Don’t be an idiot like I was in terms of leveling the site, my leveling up until a few days before consisted of “I think that’s close” coupled with some overly optimistic wishful thinking. What looked like a slight slope can add up over the course of 30 feet. Thankfully I realized we had a problem in just enough time to correct it, but we had to create an entire pad to solve our 31” out of level problem. That resulted in some panicked last-minute phone calls, some additional expense in material, and then some site work after the shed was in place to blend it in with the rest of the yard.

The result was well worth it, though. Freeing up the garage for actual vehicles and adding another garage bay was totally worth it!

I used to deliver these for a living (set-up, also).

I agree with all the above. Fine sitting on on the runners in 6 or 8 "pads"

We set them up on concrete blocks, and pressure treated shims to level. You will need to correct the leveling every few years unless you put it on cassions, or a pad. You aren't planning to put a car in there, are you?

FWIW I had the shed Co. do this for prep. It was actually cheaper than grading and putting limestone down.

We just did a 12 x 20 from Old Hickory. It’s in 4 runners and 2x6 framing in the floor. 

Ours is sitting on blocks and PT shims. Because of the location they couldn’t get the truck back there and had to essentially drag it into position, so sure leveling blocks in advance wouldn’t have really done much for us. 

My dad had oneadem pre-built sheds delivered about 15 years ago. Before it arrived he paid a neighbor (who runs an escavating company) to lay down a pad of crush n run. Nice and level, and gently sloping away from the shed. He's had no issues with it. 

What are the Runners made of?  Crush n run gravel would level and keep grass from growing underneath, but it all goes south if the wood runners rot out. I would consider railroad ties or those recycled plastic timbers.  Of course all of this depends on where you are in the country, the type of soil you have (drainage) and shed's location, on the hill vs bottom of the hill.

rustybugkiller said:

FWIW I had the shed Co. do this for prep. It was actually cheaper than grading and putting limestone down.

You planning on a rough winter? How much wood can one person stack :)

Thanks all!  There is an existing cement pad under an 8 x 10 shed. That shed is going away and the pad will be under the garage door end of the shed. Nothing heavier than a riding mower is going in there, so I think it will be plenty. It slopes towards the hillside so rainwater naturally runs off. I will shim the outside of the shed to level it.

The other half the shed is over what is currently level dirt. The plan was to dig two trenches that will line up with the runners, and fill them with cinderblocks that I have.  That would provide support and raise the shed off the ground, but will not do anything for water drainage. 

Option 2 is to dig an 8' x 8' x 4" deep hole and fill it with 2B limestone. I was hesitant to do this due to the cost until I looked up the cost of crushed limestone. I think this makes the most sense for long-term durability. It will also allow me to line it with a drain line, ensuring everything drains over the hillside. 

Photos soon if it stops raining. 

In reply to Steve_Jones :

I season my wood at least two years.

914Driver said:

What are the Runners made of?  Crush n run gravel would level and keep grass from growing underneath, but it all goes south if the wood runners rot out. I would consider railroad ties or those recycled plastic timbers.  Of course all of this depends on where you are in the country, the type of soil you have (drainage) and shed's location, on the hill vs bottom of the hill.

The sheds around here all use treated runners with treated floor as an option ( highly recommended).

We (myself and a bunch of guys) moved my sister's shed. We prepped the area by digging out the soil about 8-10 inches, and filling it with crushed granite, which was then compacted. We placed a bunch of 8x8's half buried in the gravel as supports. Gets lots of circulation underneath and stays as dry as you could ever hope for.

rustybugkiller said:

FWIW I had the shed Co. do this for prep. It was actually cheaper than grading and putting limestone down.

Mansplain please.  

In reply to spitfirebill :

I can't say for sure about the picture, but I have seen bases like that done for sheds several times before. The ones I am familiar with use 3-4 posts sunk into the ground and set with concrete just like deck supports, and tied together like the picture in rows perpendicular to the direction the shed runners (edit: or skids) are going to go. The shed is then set down on top of the framework and it's essentially just like a deck with an extra layer in the structure. I think you can see the posts in between the pairs of 2x. 

It's an easy way to get a level base on uneven ground without having to do any dirt work, but it can make for a tall floor.

Yes, what oldopelguy said. Each “ runner”? has three sunken posts. 

Shed is 10x20 sitting on 4 skids across the base. I paid $750 for the base. The cheapest quote I got for limestone pad was $1200.