I’m an amateur, having constructed a few outbuildings, now designing a garage/barn/workshop. One bay is intended to hold my full-size pick-up, approximately 6000 lbs. The full length of the front wall, where the truck will enter, will rest on a continuous concrete frost wall, with footing below the frost line. The remainder of the building will be framed on concrete piers, in part because of substantially sloping grade, for which I do not want to build a retaining wall, fill, and slab. My question has to do with building a wooden floor to support the weight of the truck.
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The bay in question will be 16 x 24. I have an essentially infinite supply of (large) red pine on my property, and access to a bandsaw mill, so I can cut materials to any size. Let’s assume I place 8†piers 8 ft. on center for that bay. Let’s further assume that I cut beams of 16 foot length, so there will be four of them spanning the full width of that bay, supported in their centers (as well as their ends). Eight foot floor joists will be hung on joist hangers between these beams, and a plank floor installed over the joist/beam assembly. My question, then, is primarily about the spacing and sizing of those joists. I’d like to use standard sized joist hangers (the ones sized for rough cut lumber are getting harder to find).
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Finally, I’m thinking about using two layers of (rough sawn red pine) planking, each 1.5†thick, the first installed diagonally and the second perpendicular to the joists.
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I’d be grateful for any advice about sizing the carrying beams and joists, and spacing the joists.
Replies
Interesting problem. I would guess an issue would be that typical home construction charts are based on a distributed floor load of 30-60 psf, whereas a p/u might be just (4) point loads of 1200-2000 lbs, each on less than a square foot (once you've driven in).
I would make sure a pier wound up under each tire in normal parking position.
Thinking about that, maybe an approach would be to consider the relatively small track that the p/u actually touches on the floor, and spec. that separately from the rest of the floor structure.
I mean, you can imagine two foot-wide strips along the floor, track width apart, reaching from the garage door to 3/4-5/8 the way to the back wall. Those 40 square feet are really all that needs to be super-heavy-duty.
Yeah! And then make the center floor between the strips removeable, for a grease and mechanical pit! Cool!
Forrest - likin' this more and more
Edits for spelling!
Edited 12/31/2006 12:10 pm by McDesign
Edited 12/31/2006 12:10 pm by McDesign
I don't like the idea of a wood garage floor; it's sure to wear quickly, and soak up oil like a sponge. I would rather use corrugated metal to form a "pan", and pour an 8" concrete slab atop it.
If you are going to be spilling oil, concrete will soak it right up too. What's the difference?
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There are quite a few old barns around here (Northern New England), that have been converted to garage use. Most of these have hemlock plank floors, which weathered a few decades of horse urine before cars parked on them. Come to think of it, local hemlock is inexpensive, hard, and resistant to decay (although incredibly heavy!)--perhaps optimal for the flooring.
Yes, Gene, I'm a third generation French Canadian, and although I've lived elsewhere, I gravitated back to northern New England. So you're right, I'm in snow country.
Thanks for the suggestions about pressure treated in strategic locations. Thanks also for directing me to the Simpson website for full 2" joist hangers.
I like the proposals for concentrating extra strength on the travel paths, either by locating piers there or adding a layer of flooring. Will have to think about a removable center aisle for a pit. I put a pit in a barn I built once, and it was mighty convenient. This one would be easy, as it would require minimal digging.
Hemlock- decay resistant ???
And now a grease pit?
Don't say a word to your insurance agent or the inspector.
Buy donuts, lots of them
Many of us, myself included and probably the OP, live and work in terror-free zones where residential construction is not inspected, ever.
Most of the Adirondack park, where I live and which makes up a huge portion of northern NY, only went to "building permits required" in the townships within the last twenty years. What that means, in most all the areas, is that some hand drawn plans on legal paper will suffice, plus a check for $15, in getting a permit.
And for sure, the inspector will never come out to see you. I would guess it is the same in the northeast kingdom of VT.
As regards hemlock, it has been the lumber of choice here for barn floors and uncovered bridge decking since the days of the earliest settlements. We get a six month winter here, so half the time the wood is too frozen to think about decaying.
Yes - more thanaverage rot resistance. In New England, what we call hemlock is Tamarack or hachmatak, which was used in small boat keels for that reason.Not the same hemlock as out west.It is extremely heavy when green and too hard to drive nails into when cured.
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That sure isn't the same hemlock we get in AK. 95% of our framing stock is hemlock. Nails penetrate fine green or dry. And trust me, it rots just great.
Our fir OTOH, is nothing like west coast Douglas Fir. Makes great kindling though
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Horse unrine all six sides of the flooring lumber.
Let's see if I have this correctly.
Building footprint 16w x 24d, truck door entry at the uphill end that is 16w.
Front edge is a single wall on good bearing below frostline, and the rest is an array of piers, and going away from the front wall, those piers are three rows of three each, all on nominal 8/0 centers.
A floorframe of this size, designed for a uniform live load of 40 psf, can handle a total of 15,360 lbs. Your truck is only delivering a point load at each tire of, let's say, 1800 lbs., which allows for some stuff onboard, plus you, and a little imbalance from front to rear.
If you think about the 1800 lb point load as a crew of four beefy framing carpenters standing close together, it doesn't seem so mammoth.
Without going into any kind of a detailed analysis, I am seeing your floorbeams, all bearing fully on piers, as roughsawn 4x10s, full-length at the perimeter, one 24 long down the center spine, and four intermediates at 8 long. You have a beamed grid of 8/0 squares, 2 wide x 3 deep.
Joists are roughsawn 2x10, 16" on center, and all run crossways, parallelling the intermediate beams.
Edit: I went to the Simpson Strong Tie website, and selected their U210R facemount joist hangers, which have a cradle size of 2" wide x 9-1/8" high. At 16 gage, they should be much more than adequate.
Thinking about where your beams will bear on your piers, I would recommend 2x P.T. caps, and maybe even a couple layers of Vycor between the P.T. and the roughsawn red pine. Your stemwall should have a P.T. mudsill, and your front "beam" should really be pressure treated material as well, since it is down there with its face in the dirt and gravel.
Your 2-ply floorframe, IMHO, should be of roughsawn 4/4 (1" thick), the first layer sheeted parallel to the long 24 length, the second layer at 90 to the first. I would go overkill with lotsa glue and screws.
There are lots of folks living in my parts with variations on your last name, all descendents of French Canadians, so I am betting you are in snow country and need to think about protecting that garage deck from winter slush and drip.
I recommend sheeting the roughsawn deck with MDO plywood, then coating it with something like a Sonneborn deck coating, a two-step process of primer and finish. Each coat goes on at 40 mils wet thickness, is a 2-part moisture curing elastomeric polyurethane, and will keep you waterproof for a long time. This stuff is used in parking garages and exterior terraces. Sand can be sprinked into the finish coating right after you notch-squeegee it to distribute it, and the backrolling you do will embed the grit into the finish. You'll get a nice floor you won't slip on.
Edited 12/31/2006 1:11 pm ET by Gene_Davis
There are dozens of those around here, old boat houses and garages and shops. This is an island so it used to be very hard to do concrete foundations - almost no sand or gravel naturally located.
The load is no problem except inasmuch as it is concentrated on the four tires, but a truck only works out to maybe 20#/SF overall in that space.
typically the framing then is same as for any other floor structure, but we normally use 2x6 T&G to decek it over. That way no sag right at the tires.
Somebody mentiond it wearing out.
That doesn't happen. The worst I've seen is rotted sill at the doors if unpainted and exposed.
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Taunton University of Knowledge FHB Campus at Breaktime.
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Do a quick call to your inspector if this is going to be inspected. Most codes require a non-combustable floor surface. That is almost always going to mean a concrete floor of some sort.
Inspector: "Is this a garage? I see an overhead door on one end."
Owner/builder: "No, it's a workshop, and the door is for getting machinery and materials in and out."
I wanted a building for my big machine and wood tools plus a place to work on vehicles. If I permitted as a "garage" I had to slope the floor which I didn't want to do. So it's a "work shop with a big front door".Steve.
Inspector: "Is this a garage? I see an overhead door on one end."
Owner/builder: "No, it's a workshop, and the door is for getting machinery and materials in and out."
Good luck with that:
Inspector: "It's got a garage door, it's a garage, no matter what YOU call it. BTW, is that floor non-combustable? Don't see a stamp on it..."
Everywhere I have lived, a building with a door large enough to admit a vehicle has to meet the garage code.
Guess it depends on where you live.Per my previous post my "garage" is permitted as a "workshop". When my gun club wanted to build a club house it had to have things we didn't feel were necessary so it is permitted as a "maintenance building".Steve.
At some point with that pickup, you are probably going to have it loaded to the max and want to temporarily hide it out of the weather. It is best to figure the GVWR rather than just the weight of the pickup.
Personally, I would run a pair of 4x6 pressure treated beams directly under and parallel to where the wheels will roll in and then place several piers under that beam. Then I think you could run the 2x6 planking across the floor. A 12' 4x6 PT at the local HD is about $25, so this detail should not break the bank.
A lot of older farm buildings used plank floors and all the spilled crankcase oil on them just seemed to help preserve them...
When I first read this I thought, no way. Then as I started to read the responses I thought, hey, this sounds like a school structural design problem worth 75% of the final grade. I like the regional responses which shows that there may be a solution for each situation depending on your resources.
I think the real problem the permit process will have a hard time to allow is the combustible floor. Drip some gas, flick a cigarette, you're on the news.
Barns (the traditional Pennsylvania Bank Barn) in my area have wooden floors of 3" thick t&g planks. There are combines, wagons and skid loaders sitting in them, and the cows live on the lower level. The beams are 10x15 in many cases. They would hold a train.
If I were presented with such an issue, I would do bar joists, vpan and concrete, unless I was after the wood look.
If you do choose wood, I have welded hangers for rough cut beams - any welding shop could do the same.