Barn foundation options?

[MushCreek]

I got the pricing in for the slab for my barn, and I'm trying to figure where I can costs. I need a slab with a footing; no way around that, but one of the options I had quoted was having 4 courses of block laid up to build on top of. This comes to $4400.00 materials and labor, which is money I could use elsewhere. If I buy them myself, the materials are about $1400.00, so I'm paying $3000.00 to have them installed.

Option 1 would be to lay the block myself. I know it's hard work, but it's only 4 courses high. $3000 is 4 weeks pay for me; I'm sure I can lay 400 block in 4 weeks! I could always just run one course of block to get up out of the dirt instead of 4 courses.

Option 2 would be to build directly on the slab, but SC is an extreme termite area, so I'd really like to get off the slab with any wood.

Other options would be to have the slab raised up some, or pour a short wall and build on top of that, or??? Code probably dictates that any untreated wood be at least 8" above the ground level.

Any thoughts on how to build a (relatively) termite-proof wood building on a ground-level slab?

[Redoverfarm]

Unless you are familar with block laying I would opt for a monolithic slab/footings and then form my wall and pour w/concrete.  Four courses of block is equilivent to 32".  Depending on the size and materials, ply, spacers, braces I think you could probably come in 1/2 of the estimate. If you figured out the linear footage and the cost per yard there are calculators on line to give you the Cu Yds.  I have the formula in hard copy that I could probably figure it out.

[Don_P]

I'd pour footings, lay the block up to whatever height above grade makes you happy and build on top of that. Gravel fill inside and pour the slab inside of the block walls. Blockwork, especially for this, is not rocket science, if you don't feel like you did a good job pour some cores or surewall it.

http://windyhilllogworks.com/Calcs/slabcalc.htm

[MushCreek]

I was thinking block on top of the slab, like they build houses here in FL, but I guess having the slab inside the block would be stronger. I've always wondered how strong the bond could be between block and slab. Either way, I'd have plenty of rebar sticking up from the footer or slab to engage the block, and I would fill a lot of the voids with concrete and rebar, especially at the openings and corners. As I fill the voids, I'll stick in J-bolts to mount my mud sill to. I don't want the slab too high, as I will have a large opening to get vehicles in and out. Although I have little experience with masonry, I'm a quick study, and I'm a tool maker by trade, so I know more about square, plumb, and parallel than most folks. My biggest problem will be not obsessing over something being 1/64" out! Even a single course of block gets me out of the dirt, and I can decide then and there whether to go up any higher. I wanted to use split-face block , which I know is more expensive, heavier, and harder to lay correctly, as I like the look of it, but I could be talked out of it pretty easily.

If I were doing the slab, I would think it would be harder to do a slab inside of a wall, although they do it every day in basements. I could probably even handle the slab pour myself, although I've never done one that big (28'X48') and I'd like a reasonable flat, level floor, as this will be my workshop.

[JRR]

.......I was thinking block on top of the slab, like they build houses here in FL, but I guess having the slab inside the block would be stronger. I've always wondered how strong the bond could be between block and slab. ..............

Not sure I understand your assumption here ....  I would choose a block wall atop the slab.  There are a number of ways to "attach" the block to the slab ... usually envolves sticking several 1 1/2' lengths of rebar along the center line of the block wall into the wet concrete of the slab.  Try to locate so they will be in the block voids ... but any that miss can be bent over flat or snipped off with a cut-off disc on a rotary tool.  Using pre-bagged mortar mix would be the simplist way to go probably ... I would suggest buying some bags of Portlant cement to add to the mortar mix, not too much ... makes it stronger and easier to use.  A mechanical mixer is a great tool to have ... even if you use pre-bagged mortar.  Not absolutely necessary ... just makes life a lot easier.  I like to keep the outside of my wall clear of mortar "mess" ... no mortar drops down the blocks ... no accumulations at the lower corner of the wall.  This makes it easier to later apply surface bonding cement or any other surface application.

Even tho I am just a hobbiest, I have become fairly skilled at laying block and stone.  Pretty much fun, I think.

Make sure the slab is poured on clean compacted (or virgin, undesturbed) earth...free of any organic inclusions.  Make sure it is deep enough to meet frost requirements for slabs in your area.  I have used slab concrete "forms" of corrugated steel ... cut from roofing ... supported/wired to rebar driven in earth.  No wood.  To avoid wet concrete break-outs, a backfill of stones is placed before the pour.  A bit of work and some expense. Good for termite areas.  Doesn't have to be removed.  Of course, you may be fully "trenched" ... not requireing any forms or retainers.  Just depends.

[Don_P]

When you put the block on top of the slab, the slab is structural and some thought needs to be given to making sure it cannot settle or it becomes suspended and that needs to be thought out. If it is inside of the walls it is more like a rug, just a mat to be driven on and if it needs to float or settle it is free to do so without affecting the walls.

[MushCreek]

I'm going to have the slab and footer done professionally- just too big to tackle DIY. Specs call for 2' thick at the footers, and 6" everywhere else, plus 2' square pads of greater depth where internal load-bearing post will set. It will be one big monolithic slab, and I think it'll plenty for the intended purpose. They've spelled out the rebar schedule and the concrete strength- these guys do this for a living. This will be in SC, so frost line isn't an issue, nor is snow load, seismic load, or wind load, although I like to over-build. Regular block is $1.15 at Lowe's, and I'm sure I can do better buying 400 of them. I'll have the concrete guys put the rebar for the wall into the wet concrete. They're also going to stub in the drains for the bathroom, and a conduit for electric while they're at it.

[JRR]

.... reads as though its gonna be a first class "barn"!

[MushCreek]

It will be! I've had a life-long dream of having a big garage with a small house out back, and this is my one chance. The main floor is 28 X 48, and the loft is 28 X 32. One third of the main floor will be separated off to make a seasonal great room for entertaining, and as guest quarters should we ever have over-night guests. That's why it's getting a full bathroom. If our plans go awry somehow, it could easily be made into a house. The rest of the main floor will have a machine shop, wood shop, and maybe an automotive lift in the center. My wife will have her own garage attached to the house. For the time being, it will have T1-11 siding and a tin roof, but if I win the lottery I'll put Hardi siding on it to match the house.

[JRR]

You may need 6" (min) reinforced slab thru-out.

Some miles south of me, there is a home/work site much like you describe.  This building is rather huge ... I would guess 60' x 200' or so.  The 60' side faces the road.  High roll-up doors across half of the front for shop access.  I think this guy works on over-road trucks and earth moving rigs.  25% of the building front is dedicated to family living space.  The whole thing looks great ... all trimmed in detailed painting, wall - mounted planters, iron-work, real-shuttered windows, etc.  The living area looks like a home ... and the shop area looks different but complimentary.  There are no other buildings ...  painted concrete driveways wind thru lawns, shrubs and trees.  I would like to take a photo, but want to first get permission. Today, I'm sure the code-Gestapo's would not allow such a venture to be built.  Its been around for some years ..."grandfathered", I suppose.

Good luck with your plans.