Any Civil/Structural Engineers in the HAMB house?

I would look at a concrete deck on a pan as IIRC building code will require a garage to have a non-combustible floor. There was an article in the last Journal of Light Construction magazine on this. You can get an article reprint online.

 

Yes it can be done.

First, what kind of wood? Different wood has different strengths. If in doubt, assume a lower strength. When in doubt, overkill.

Second, you need to know your loads. How heavy is your car or any possible car that will be parked on the deck? Will you have specific tools that are heavy in any one location. Are there heavy items that can move? A rolling toolbox is extreemly heavy. A refrigerator full of beer?...if it is free beer, that means a garage full of us HAMB guys.

IF I were designing it, I would use a 6' joist span between load bearing support beams. Run the joist full length (18 feet) with the support beams beneath them at 6 foot spacing. The full length joist is much stronger than 3 short pieces. Do not plan on using a 9' foot joist span. It will deflect. I would use 2x10 floor joists on 16" centers (personally I would also change to 12" centers under the car / tool area.) You neglected to mention the flooring. Will it be it 2x6 planks or 3/4 T&G plywood or 1" planking? That will make a difference too. I would look at doubling the flooring, running the first layer at a 45 degree angle and the second finish layer perpendicular to the floor joists. Remember, the shed has weight too, so it must be considerd in the foundation. You will also have rain loads, live (people) loads, that refigerator full of beer load, and your massive hurricane wind loads.

Again, my thought is that 2x10 joists on 16" centers on a 6 foot span will work fine, provided you have a strong floor and strong support beams too.

If you have a building department, they will typically run the calcs for you for free. If code requires non-combustable (concrete), then use it. Do it right the first time.

 

A friend had several cars stored in an old barn -- wood floors held up by wood posts (which were actually trees, if you've seen old barns you'll know). These were heavy cars, including a 49 Merc...

Engineered wood beams e.g. glulam would work...

If you need a building permit you will probably have to have the structure engineered, and most big lumberyards will do that for you.

 

The floor joists and sub flooring is pretty straight forward. 2 x 8 treated on 12" centers with every fourth joist being (2) 2x8 with 5/8 OSB sandwiched to serve as pier beams. Then 2 x 6 for sub-floor. Then you can add whatever flooring on top for smoothness or appearance.

THE TRICK IS... your piers.
You describe the soil conditions as sandy, possibly nothing but sand over 4 feet deep. You will need concrete piers every 4 feet both directions, but again it doesn't sound like you will be able to put your pier deep enough to prevent shifting. You may look at other similar sturctures in the area and see if a flat shallow pier was used insted of a cylindrical deep type; in other word a 2'x2' concrete pad every 4 feet.


Your real question.. How much material? A SHIT LOAD! example you will need 1332 feet of 2 x 8 just for the joists.

 

Where I live, everything is supposed to have permits. People sneak decks and porches in all the time and fly under the radar. Do a big shed/garage and all it takes is 1 neighbor with a grudge to turn you in. They may not even let you store a car inside of it.

Bob

 

Hire a professional.....

 

My great grandfather had a shed with wood floors too. He kept his Dodge trucks parked in it for decades.

I'd prefer to avoid arguing why not to do it and try to hear advice on how to get it done.

I can build it, and I plan on doing just that. I just would like to know how it should be done.

If I am totally honest, the attached garage will be where the major construction happens, the shed will be where minor wrenching and storage goes. The motorcycles and lawn equipment are constantly under my feet when I am in the main garage and I am forced to push all of it out into the driveway whenever I am working on something. The shed will allow me flexibility and S-P-A-C-E.....


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Hey there -

I am an architect in Illinois. Designing in Iowa is about the same for IL (snow loads, dead loads, etc.)

Designing the "deck" is a pretty simple process. I think I would design the entire structure to support the load of the car. Remember you will have more stuff in the garage.

Start at the top and work your way down meaning the deck, then the joists, then the beams and headers, then the posts or lower walls, then the foundation.

I have just finished designing an elevated water tank stand that needs to hold 1600 gallons (+/- 13,500 pounds). Up in the air enough so a truck can drive under it. We ended up using some heavy stuff. Pay close attention to your columns and foundation. What kind of soils do you have? Do you know the bearing capacity of the soil?

I would love to help you out so give me a call at 847-683-4386.

Jay Stockbridge
Stockbridge Architects, P.C.

 

I understand all of these things. None of that should be of concern to the deck and how it should be built.

I really do appreciate all of the concerns and the cautionary red flags. At the very least I can tell that you care enough to try to bring it to my attention. And I do want to thank you all for your opinions, they all matter. I get the same reaction when I talk to my friends.

I have heard a number of times how crazy I am for wanting this. That doesn't make the thirst go away....

I'll worry about the codes and the neighbors and all of that jazz, what I need is specs.



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I had a professional framer advize me on a 8 ft. wide mezanine in my garage He sugjested I go 2x8 floor joist because of the room up there for engines etc. I followed his advice and am happy with the result. I can throw a lot of weight up there.

Someone already made a good point about equipment trailers having a 2" decking. My car hauler has had some heavy stuff on it, and it only has 2x6 decking with support every 2ft. I would go with a toungue and groove or two layers of 3/4 ply for floor. As wood dries it shrinks. The last thing you want is dropped tools and fasteners dissapearing through the cracks in your floor.

Remember that you can make adjustments in your design to suit your desires. If you don't want the thing requiring a set of stairs to get up to you can narrow the width of the joists and space them closer together, that sort of thing. Hope this helps. I'm not certified, but experience counts for something.

Doug.

P.S. Why not put together a portion to put a car on and see how it performs. I know, no specs, but I'm only trying to help.

 

My cousin in Calif lives in a landslide area. He built a 24 x 30 garage using an I beam substructure and a laminated wood floor. Worked out great.
You could do something similar with a wood substructure. I might recommend you run your floor members parallel with the wheelbase of your car and space them so the tires will be sitting over the longitudinal members.
Laminated beams are killer strong! You CAN do this!

(BTW, my son is a CE. He helped me design the trusses for my 30 x 40 garage. I thought they were too puny, but he proved me wrong. )

 

If you have access go look at some old warehouses.
Most of these are 2X12 on 12'' centers with 2'' t and g flooring. They dont usally exceed a 16' span. Most are yellow pine which has a better structural rating. Go goolge span charts and lumber species and this will help.
Solid wood has a better crush than most plywoods for this app.
All of this will be available in the charts for live and dead loads, and this is the same info engineers will use.
National or American Lumber Institue comes to mind.
There is nothing wrong with a wood floor, except for fire or termites, which both are a matainence item

 

Here is the lay of my land.
As you can see the main garage is attached and I will build a pass-thru door out the back side of it in order to drag the motorcycles ( or hot rod ) back to the shed.

My uncle lives not more than two blocks away in the same neighborhood and has a dirt floor shed of similar size that is not called a garage, per se - at least not with whom it matters (tax man). He parks his truck in it all the time.


I may end up shrinking my shed down a tad in the end - the spare room is just a bit of gluttony....

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I built one about 10 yrs ago 16x25. Used cinder block supports on 6' centers with 2x8 jousts and 21/32" subfloor topped with 1/2" mdf tongue and groove. Walls and roof of 2x4 studs, 2x8 rafters and a second level of 1/2 plywood full width and 8' deep for storage. Held 3700# car, tool boxes, work bench and riding lawn mower. It was fine when I moved 4 yrs ago and as far as I know is still being used but not as a garage.

 

just my .02 stop listening to all the bs and go talk to the building inspector in your town or get a copy of the building code you will have to adhere too . otherwise your work maybe for nothing. as they tell us down here in fla. i don't give a crap how you do it up north this is fla and this is how we do it

 

Seems to me the easiest way to accomplish this would be to lay a wood deck over a cement slab.

 

Working on elevation...

We survived the last two 500 year floods without a drop of water damage near my neighborhood. Soil is a clay mix...

Trying to get actual values via GIS.


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I can see the wisdom of a wood floor. That what boats are made of and they float.
Being surrounded by the Mississippi river is a consideration not to be taken lightly!

I had a friend want to build a shed on a flood plain and the local building dept told him he could not do it.

So... he placed heavy beams under it and called it a raft.

 

I should mention that I am not near the river anymore, but I was when I signed up to the HAMB like a dozen or more years ago. We moved to this house a couple years ago. Never changed my loc info. I still live near the island and my folks are still there along with my heart...

Soil:

ATTERBERRY SILT LOAM, 0 TO 2 PERCENT SLOPES

I live on the bluff now so elevation is at 690 feet - that's in Iowa State Plane South - and that's an Ortho Height...







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Bldg code here requires noncombustible flooring surface and sloped

 

Maybe I just go redneck on this and build a car trailer on blocks....hahaha...


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I'm a structual engineer and have lots of imput for you to build a deck that your rod won't fall thru. Spec's depend on the size of the deck. feel free to e-mail me. [email protected]

 

Professional Civil Engineer here! To cover the cost of my effort and my professional liability insurance, I charge $195/hour.

 

Retired engineer here...
Quit screwing around and hire the proper help to do the proper job.
Depending on many factors, elevated structures should not be built haphazardly 'just because you have the timber'. Properly designed plans have more than just a lumber schedule attached....

.

 

If I were consulting you on this project, here is what I'd tell you; build a slab-on-grade using traditional (hah!) methods native to the region. I'll assume it's the same as most anywhere else; reinforced concrete footings below the frost line (for those in cold climates), a 4-inch deep gravel base and a reinforced (with welded wire mesh) concrete slab at/just above grade. Then (after the building inspector leaves, lol) install whatever wood flooring you want atop the slab after laying a 6-mil plastic sheet to prevent moisture wicking .

Yes, I'm a PE, and that's how I'd do it. But I'm not telling you how to do it, nor am I advising you on this matter. All rights reserved. lol.

 

A man never can have too big a deck!

My wife says I have a big deck!

 

So the soil has changed from sand to clay?

 

use 2x4's standing up like they used to pave race tracks. it will take alot but will hold more than the structure supporting the floor.

 

Is it safe to assume you are going to do this without any permits, or city or county knowledge?

IF this is not the case, this is big waste of time. Don't you think that going to the city and asking what they REQUIRE would be the first step? Don't you think they will require nothing less than what is sufficient for your structure?

I don't mean to sound like a jerk but why would you not go the the horses mouth.

I just build a shop behind my house on a seperate lot we purchased for that purpose.
Believe me, I would have much rather went wider, but had a spent $1000 for plans to be drawn up that would cater to my wants rather than what I can realistically build, I would have been a pissed dude?

I can completely understand wanting hamber input on style, design, etc. but,
What is the reason you don't want to ask the city first of the requirements?