Slab elevation, overhang, and frost walls

[Daddydavesr86]

Purposed Building is a 16x32x12 pole barn in centrel ky.

Based on what i have read my slab elevation should be min 5 inches above grade? Just kinda confirming. Shop location end of a driveway. Driveway slopes down diverting water down and away from house towards one corner of the new purposed shop.

Building overhang?
Do i need one? How much? More for looks than rain control?
Can i install gutters with out over hang?

Do i need a frost wall? Im in centrel kentucky.
Im planning on having a pole barn built. Builder plans show 18 inch diameter hole with 9x18 footer plus 45 inch back fill sand and gravel compacted then that would put height of bottom concrete slab. Then 4 inches of slab.

Vapor barrier concrete? Is this installed on gravel base prior to concrete? Or under gravel base?

 

[ixlr8]

On my shop I put an 18" overhang all the way around the building. I like the way it looks and it helps keep the rain water away from the building, as long as the grading is done properly.

 

[matt_i]

On the endwall the overhang has to be added. Usually with trusses along the length of the building the overhang is easy and free.

I recommend gutters as you have complete control of the water rather than allowing it to splash down. The dirty splash can be controlled with "clean" stone but the stone also has to be kept clean of vegetation.

The proposed foundation should be frost protected. The posts bear the load of the building and lie on soil that theoretically won't ever freeze assuming typical climate conditions. It might be a good idea to thicken the edge of the slab even if merely earth-formed. I would take a look at steel reinforcing of the slab -- wire mesh panels are good.

I placed the vapor barrier directly under the slab, and atop the crushed stone base. I used 3/4" nominal washed limestone, in some areas of the US its called #57-stone (as opposed to the #22A "crusher run" including fines down to dust). Its my opinion that the dust/fines can continue to settle over a period of time and lead to voids under the slab whereas the washed stone, once compacted is there to stay unless the stones themselves start to fracture and breakdown.

 

[Firebrick43]

The bigger the over hang the better the walls/windows/doors are protected from driving rain. I personally think 24” should be minimum. 36” to 40 will slow for a protected sidewalk if needed. Also overhangs allow for more insulation at the edge of the wall(energy heel)
You can install gutters without an over hang but if there is a dam and the over flow under the roof the are tight on top of the wall and that water will enter the wall. The same scenario with a soffit isn’t great but doesn’t saturate the wall.

Plastic should always go over the compacted stone.

3/4 clean crushed stone at least 2 times the slab depth (3 better) is best practice. It should be placed in 4” lift and compacted with a vibrating plate. Do NOT let the contractor compact it with his skid steer like so many try or place it in lifts greater than 4” (6” if the use a big ride on roller.

No frost wall needed on a pole structure, some 2” foam buried on edge about 2’ deep is highly recommended to keep frost from creeping under and help with heating efficiency.

If you plan on heating the building 2” of XPS foam is recommended under the floor or even 1” if you can’t afford 2. I will make a big difference in heat bills down the road. Double bubble insulation is snake oil and worthless under a slab.

5” above grade should be fine dependent on surrounding grade. If slab is down hill from surrounding grade you may want more. Also probably more important is a perimeter tile or French drain to keep water away from the poles.

 

[Daddydavesr86]

Thank you for the post and information.
I was told the frost wall will protect the slab from cracking.
I think the term heaving.
Is this something i should be concerned with.
My buddys building is little different.
He used metal building require different concrete specs and pillars poured.

Thank you all