We are considering putting a deck on our 20 foot wide town home. The back of the home has a 2 car garage and a driveway and the deck will be directly above the driveway.
Are there any special considerations while putting a deck of this nature? Do you recommend more than 2 wood beams to hold the deck?
Thanks
SR
Recommendations? Hire a structural engineer, this puppy is huge. Setting posts & beam in the middle of the driveway to cut the span down to manageable size would still require some serious wood beams and joists. And that would not be eye appealing or safe. Come home drunk and end up with who knows how many tons of lumber on your head - ouch!
I built decks a long time ago (80's) and just to give you some perspective: At the time 2x6 treated pine joists 16" O.C. were rated at
8' max. span. So you are looking at 16" O.C. 2x8 joists with solid blocking over 3 beams to create two 10' spans. For a car to pass under requires a height that throws you into 6x6 post range. Beam size depends on post spacing, beams of doubled 2x10's for 6' to 8' post spacing is reasonable here.When I was doing this sort of thing for a living there is no way I would take on this job without an engineer, its just too large. This is not a do-it-yourself thing, consult a pro at least in the design stage.
John
I think you mean only as wide as the garage and not the whole house, but you don't say how wide. Of course a 2 car garage is nearing 20 feet.
While you're at it, maybe you can turn it into a carport. Then I can visit and leave my convertible top down even when it's raining. Or someone has stuff in the back of the pickup.
If it is attached townhouses, you likely have an HOA and/or CCRs on the deed and/or local code that dictate what you can build, especially if the front yard isn't very deep. Check those out before you spend any money.
Aside from the fact that I believe it's a backyard deck, it's good advice. Add-on decks are frequent subjects of news articles like "Deck collapses injuring 20" because they are often built ad-hoc by people who are not quite up to the engineering part of the task.
-- Bobby G.
Yeah, but . . . homemade decks are often built by people who didn't just guess wrong about loading factors or stress vectors. They just didn't even know about that stuff and threw some lumber against the wall. Hell, some of them don't even know about triangular bracing and their decks collapse like a scissor jack with stripped lift screw.
Back in the days when I was a police reporter three things happened like clockwork in the hot summer months. Toddlers drowned in swimming pools, babies and dogs died in locked up in cars and homebrew decks collapsed. I guarantee they'll be one coming up this Fourth of July. Drunk people overload the deck and can't hear the squeaking as nails pull out just before the crash.
The collapsed decks I've seen were pretty much "gee, I wonder why it took so long for this inadequately braced and nailed together POS to fall?" Everybody knows someone with a deck like that. It's the American way. (-: DIY, even if you don't know exactly what you are doing.
And yes, PE's make bad mistakes too. My dad was one of many that helped investigate the infamous Hyatt Regency walkway collapse. The structure, though a series of communication mistakes, was barely sufficient to support its own weight, let alone that of spectators. Over 100 people died.
-- Bobby G.
@newbee:
Is there a Homeowner's Association (HoA) for your townhouse ?
If yes, then they would have to approve of any modifications to the external appearance of your town home... The HoA board or management company will have more information for you about how that process works and what size and design the deck can be along with the requirements for the insurance your contractor must have and the correct legal names for the "additional insureds" your contractor will have to produce certificates of insurance to cover...
If not, then hire a contractor who is familiar with the requirements of your local AHJ as far as the construction of proper code-compliant decks... Just be aware that your design might be driven by whether or not your deck or anything adjacent to/underneath is considered an egress pathway from your house... That generally means some sort of fireproofing as a design factor in your deck...
~~ Evan
first check if its legal in your community.
anyone else do the same thing? take a look at their construction, and ask your local code enforcement officer
Use the span charts for your joists. You're going to need some pretty big lumber. How wide is the driveway?
Pretty much the same support as needed over a single door (though the side under the roof line), no? No people load, there, but roofs weigh quite a bit.
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