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  1. #1
    Join Date
    Aug 2008
    Posts
    35

    Default Deck weight limit

    My driveway ends with a 4' drop onto my side lawn. I was thinking of extending the driveway by one car length by building a pressure treated deck. I'd like it to be strong enough to hold a car but the only purpose is to park my motorcycle trailer on it. With both bikes in it the trailer it could weigh as much as 3k pounds. I believe a normal deck is built for a 40 psf live load. What would one strong enough for a car be?

  2. #2
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,356

    Default Re: Deck weight limit

    Let's do some calculations. Let's say your trailer has four tires, each inflated to 30 psi. 3000 pounds divided by 30 psi means a tire contact area of 100 square inches (25 square inches per tire). A square foot is 144 square inches. So each of your tires weighs 750 pounds in an area a sixth of a square foot (about 5x5 - further calculation puts this at about 4300 psf); your deck needs to be able to support that much weight in that spot.

    That's not to say the the entire structure must be able to support 4300 pounds loaded on every square foot simultaneously, but your average backyard deck isn't built to handle that much point load. Were the 4300 pounds evenly distributed across the entire deck, it might be OK. A standard substructure may be able to handle the load, but the decking itself must be able to transfer the weight to a larger part of the structure than standard decking would.

    P.S. -- at 200 lbs, a man with a size 10 shoe exerts probably around 600 psf point load. And don't even ask about the lady with stilettos.
    Last edited by Fencepost; 02-05-2012 at 10:26 PM.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  3. #3
    Join Date
    Aug 2008
    Posts
    35

    Default Re: Deck weight limit

    Thanks, Fencepost. That explains a lot. I would like to have an architect draw up the plans to take to the building inspector. I was interested, before i do that, in finding out what kind of structure would be necessary. IF it was pretty much 8 x 12 deck with extra support it would be feasible. If it would turn out to be an elaborate structure with steel beams and massive footings the cost wouldn't warrant a parking place for a utility trailer.

    I was thinking something like 4 short 6 x6 posts on typical concrete columns below frost line. Each directly under where the parked tie would rest. 2 triple 2x10 beams running the same direction as the travel of the wheels onto the deck at 7' apart with 2 x 8 joists and 2x4 decking. The posts closest to the driveway would be 16" high and farthest from the driveway would be about 36" high.

    A little over built for 8 x 12 deck but cost wise would make sense for the convenience Iím looking for. If more would be required then itís probably not worth it.

  4. #4
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    5,073

    Default Re: Deck weight limit

    A deck like you are planning needs to be permitted and to get approved you need to show your plan checker a plan signed off by an engineer.

    Since there will be costs involved, you have to ask yourself if it's all worth it for you.

    A car parked on the deck is like having the entire New York Giants Defense squad on it...without collapsing.

  5. #5
    Join Date
    Oct 2008
    Posts
    116

    Default Re: Deck weight limit

    Wouldn't some type of fill, perhaps surrounded by and contained by, some appropriate landscaping blocks, etc. be better?

    The problem with a deck is that, although you will all you can to prevent it, somebody will drive on it. It may be somebody turning around, backing up, the UPS or FEDEX guy accidentally getting a wheel on its edge, etc.

    Good luck.

  6. #6
    Join Date
    Aug 2007
    Location
    Maryland
    Posts
    1,157

    Default Re: Deck weight limit

    Good point about a retaining wall. Look at the dry stacked block like Pavestone's Anchor retaining wall. Lots of companies make similar products.

  7. #7
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    5,073

    Default Re: Deck weight limit

    A retaining wall is a good idea, though more involved. Plans, permit and inspections required.

  8. #8
    Join Date
    May 2011
    Posts
    251

    Default Re: Deck weight limit

    With only a 4' drop, a vertical retaining wall made of concrete then pour a concrete pad. It might not cost as much as you think.


    Otherwise, time to look for a lighter folding open trailer. Sounds like you have an enclosed trailer... or at least soemthing pretty substantial.
    1925 Two-Story Stucco Beaux Arts Neoclassical

  9. #9
    Join Date
    Aug 2008
    Posts
    35

    Default Re: Deck weight limit

    @ Cougars1996,

    We did consider a retaining wall but it will bury the Basement windows and also prevent my neighbor from getting his lawnmower from the back of his house to the front. His driveway was just like mine and he filled his in. Now he has to use my yard to get his lawnmower up front. Itís much higher on his property.
    I do plan on having the plans drawn and approved by building inspector. I was just wondering if my plan was feasible, can you build a deck to hold a car (just in case as cougars1996 stated). Just wondered if any one knew what the specs would have to be for that type of load. To get any idea of what was involved before going to the Building inspector.

  10. #10
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    5,073

    Default Re: Deck weight limit

    To get your plans approved by the building department, you'll need them signed off by an engineer (that's true in my city, and I'm sure in all other cities). Why don't you check with your bldg dept first, then get estimates from two engineers.

    Please keep us posted.

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