Concrete floor on shed

[Brian Kent]

I am moving to a house that has a concrete pad for a storage shed. I plan to assemble a wooden Borg shed for storage, to keep the garage clear for the shop. So my one concern is best moisture protection for cardboard boxes.

Is the concrete floor enough? Should a get a kit with a wooden floor to keep the bottom row of boxes off the concrete? I could also just make the bottom shelf a couple of inches off of the floor.

I don't know how a wooden shed attaches to the concrete pad and how it seals. Any recommendations?

[Lee Koepke]

i wouldnt store concrete boxes directly on the floor in a shed. between the wicking of the moisture thru the slab, and the inevitable water getting under the sill plate, you are better off.

They also sell what's called a 'sill seal', essentially a 4" wide neoprene washer roll that you'd put under the bottom plate, that helps with water coming under the sill.

[Darin Higginbotham]

To fasten the shed to the pad, probably the easiest way would be to drill the sill plate with a ordinary wood bit and then use a hammer drill to drill into the concrete. Get some expansion bolts, drive them in and nut them. You might be wise to check local codes for specs on bolt size,spacing,depth of hole ect. ect...

[Don Alexander]

personally i would put a wood floor in it and use some 2" solid concrete blocks to keep the wood off the concrete any wood touching the concrete blocks should be pressure treated

[Andrew Nemeth]

I would not store cardboard boxes directly on concrete for extended periods of time due to the previously mentioned moisture issues. I have had boxes stored on concrete in dry areas break down over time (several years). I however, would not use a wooded floor as I want to see the moisture if it's there. I would either use plastic bins on the floor or build shelves with a shelf right at floor level, leave the shelf off a few areas so you can roll in other items (lawn mower, wheel barrow, ext).

[Bob Riefer]

+1 on plastic bins. They last forever, and you'll be happy for moisture and critter reasons forever.

[John Gustafsson]

Anchoring the shed, expansion bolts work as mentioned. Another option, the Remington explosive nail driver. Drives a hardened nail through the sill and into the concrete. They don't pull out. Didn't notice where you were, but there may be minimum wind loading issues. Around here along the coast almost all jurisdictions require 100 mph capability and require a permit. For a small shed the permit is usually free but they want to check it for that wind requirement. It usually requires rafter/ roof truss clips as well. Inspectors will have a minimum number of anchors that they want.

Seal to Concrete, Neoprene boot is great, think about sealing tar in a cartridge and bed the treated sill into that if you cant find the boot

[Jon Endres]

I recently built a 16x20 shed (more like a short 1-car garage) with a concrete floor. Used for storing my rough lumber inventory, plus all the miscellaneous crap I don't want to keep in the house. The concrete floor gets not-quite-damp in the summer, so anything that's stored on the floor is either in plastic bins or on a pallet. I try to avoid cardboard of any kind in the shed anyway, as I've had bad experiences with rodents and carpenter ants. If there's any cardboard it's something that doesn't matter, like case boxes for canning jars or something like that. I tried to minimize moisture by putting 6" of crushed stone under the slab and a 3' drip-strip all around the perimeter, but it sounds like you may be too late for that. Positive drainage cures at least 90% of concrete moisture problems.

[Von Bickley]

Brian,

If this is an existing slab, you are probably out of luck on the moisture issue. On a new slab, you would put down plastic for a moisture barrier that would help keep the slab dry. Too late for this.

Fastening the building to the slab can be done with PT construction adhesive or liquid nail with the Remington nail driver. The Remington single-shot nail drivers are not very expensive and nice to have around.

In the area where I live, we don't need a building permit for small jobs that are less than 500 sq. ft.

In the building you will want pressure treated lumber where the wood comes in contact with the concrete. You will want a pressure treated bottom plate or sill on the building. If you build shelves or cabinets, you will also want to use pressure treated where they come in contact with the slab.

Hope this helps......

[Brian Kent]

Yes, the slab is already there.

I'll use one of the water barrier ideas to keep water from leaking in, pressure treated lumber for anything that touches the concrete, and probably plastic boxes on the bottom shelf for safety.

If I were to buy either a single shot nail driver or a hammer drill, which would be more useful to have around?

In this area I can build a shed up to 10' x 12' without a permit.

The picture shows my wife standing on the slab. I will get whatever fits on the slab, but I am guessing guessing it could be close to 10' x 12'.

[Von Bickley]

If I were to buy either a single shot nail driver or a hammer drill, which would be more useful to have around?

The picture shows my wife standing on the slab. I will get whatever fits on the slab, but I am guessing guessing it could be close to 10' x 12'.

A hammer drill or a single shot nail driver?

You will get more use out of the hammer drill, but you can get the nail driver for $32.00 from Amazon. Get both.


Looking at the picture of the slab, you will definitely need to work on a way to divert rain water around that slab. You could do this with some type of natural berm, raised flower beds, or small retainer walls, anything to keep water away from the building.

[Stew Hagerty]

First of all get a roll of polyethylene sill sealer (http://doitbest.com/Insulation+and+h...sku-112305.dib) from your local Home Center. Place a layer under the sill plate of your shed. Shoot powder actuated fasteners (http://doitbest.com/Anchors+and+sett...sku-300533.dib) through the sill plate directly into the concrete.

If you are just going to store a few boxes of weatherproof items plus things like the lawnmower in the shed, just stick with the concrete. If, however, you plan on using it for anything else, then definately spring for the wood floor.

[Jacob Robinson]

To fasten the shed to the pad, probably the easiest way would be to drill the sill plate with a ordinary wood bit and then use a hammer drill to drill into the concrete. Get some expansion bolts, drive them in and nut them. You might be wise to check local codes for specs on bolt size,spacing,depth of hole ect. ect...

actually, you can drill through the sill plate with a hammer drill just fine. saves your wood bits from eating concrete as well. everything else he said is spot on, expansion bolts, the kind with the spike you nail end to expand them, are the way to go. When you are doing that, I recommend putting the nut on and keeping it at the top of the threads to protect them, so a missed hammer swing does not ruin the threads. Some people like to shoot some adhesive down the hole ahead of the bolt, but its not required by code anywhere as far as i know.

:edit:
additionally, I would like to mention that pressure treated wood is only a guard against termites. Some people have the misconception that it somehow protects against moisture, which is not the case. definitely use it if your area has ground termites, otherwise you'll be rebuilding your walls in a few years.

I recommend against the remington nailers, especially if the slab has been there for quite a while, the old concrete can be very hard, and the remington nailers can have a hard time setting nails into it. drilling for expansion bolts becomes faster very quickly, especially on small jobs like that.

[Andrew Nemeth]

If you are in the market for a hammer drill, I would install the sill with expanding fastners or allthread into epoxy. I use Remington power fastners on occasion but only in very dry conditions and mostly as a temporary fastner.
I have repaired or replacd quite a few projects (originally done by others) where the fastner has pulled out becuase the concrete shattered or the fastner rusted.

The remingtons have their place, and I must admit they are fun to use (shooting a fastner into a steel I-beam is something to see). Ah, the smell of gunpowder in the morning! But, they are not a substitute for a real hammer drill in most situations.