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Old 11-01-2012, 08:29 PM   #1
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detatched 16x20 deck on piles


so i have this deck to build. its 20' wide against a house and out 16'.
grade is 8 inches from the top of the deck. The ground is very tough. lots of hard rock and seems to be very sturdy. I dont want to attach it to the house (permits needed and a PITA)
heres my plan. 3 rows of 3 piles 16" deep x8inch holding a saddle. then a 2 ply 2x8 treated beam running the 20' length down each row of piles. the beam top will be flush with the grade allowing me to use 2x6 treated lumber for the joists and top it off with 5/4" deck boards. only problem is im worried about heaving but the ground is super solid (almost impossible to dig in with a shovel) and the spans between piles are near the maximum allowed here in canada so if it does heave its spread out over a longer distance.

does anyone see any problem with doing it this way?

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Old 11-01-2012, 08:40 PM   #2
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matty,

check out the American Wood Council's "Prescriptive Residential Wood Deck Construction Guide." This is based upon the 2009 International Residential Code, basis for most local and state building codes. It should answer your questions.

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Old 11-01-2012, 09:00 PM   #3
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GBrackins has given you the link for the IRC deck building code. Of course, from your description, your deck may not be subject to code, and it sounds like you do not need a permit. This would allow you the flexibility to design based on any code you choose, or to custom design the deck based on fundamental engineering principles, or to just wing it and build it any way you choose. It is impossible to evaluate whether your plan is OK unless you tell us what your design basis is going to be. If you want to build to IRC code even though that is not mandatory, then you really need to start by reading through the code, as it discusses in considerable detail essentially every aspect of deck construction.
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Old 11-01-2012, 09:12 PM   #4
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Ok. I have the Canadian building code and the spans and everything meets code its just the code says that if the deck is stretched to the house then it needs piles as deep as the footing (if within 5 feet from the house) ill take a look at the link and see if it sends me in the right direction
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Old 11-01-2012, 09:16 PM   #5
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yes if you have piles within 5' of the house then the pile must extend to the same depth as the footing of the dwelling. this is because all footings (and piles) must bear upon undisturbed natural material. when digging for a foundation the excavation is always more than the size of the dwelling. typically within 5' of the dwelling the soil has been disturbed, thus the reason for going deeper. make sense?
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Old 11-01-2012, 10:52 PM   #6
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i was trying to steer away from that since it is not attached to the house. i figured that if you can float a deck on deck blocks then the small pile is essentially the same thing its just buried 2' deep. i cant get a bobcat in the backyard to drill through the hard rock and dirt so the piles that deep are not really an option for me. the house is a basement entry built into a hill and the deck is off the dining room which is on the second floor
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Old 11-01-2012, 11:19 PM   #7
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where are you located? do you know what your frost depth is?
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Old 11-01-2012, 11:44 PM   #8
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in british columbia. its about 36 inches
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Old 11-02-2012, 12:24 AM   #9
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I'm not up on the National Building Code (Canadian). Reason you should have your location listed in your profile.

in the states if you build a free standing deck that is not supported by the dwelling you are not required to have footings (depth) below the frost line (except the must bear upon undisturbed natural material or engineered fill).

With that said, the piles must be capable of supporting the load they impose on the ground. if the soil has been disturbed and not properly compacted they can sink. unequal sinking will cause members to twist. not a good thing.

if you are required to have a permit to construct then you must follow whatever the code requirements are in your jurisdiction. if you are not required to pull a permit then you can do pretty much whatever you want, of course realizing it may lead to problems.

if building a ground level deck you may consider a patio. if elevated deck you should install lateral bracing as shown figure 21 on page 14. this prevents the racking of the deck. with a free standing deck it should be done on all corners, as well as intermediate posts along the perimeter.

make sense?

Good luck!
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Old 11-03-2012, 09:51 AM   #10
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interesting. as i am going to build a deck myself, hopefully next summer.

i also am going to do a floating deck. i was planning on cantilevering it over to the house. perhaps this will work for the OP ? how far is a safe overhang ?
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Old 11-03-2012, 09:53 AM   #11
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oh. what is "racking" ?
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Old 11-03-2012, 10:01 AM   #12
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Swaying, moving from side to side.
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Old 11-03-2012, 11:22 AM   #13
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Quote:
Originally Posted by Mattyboy89
so i have this deck to build. its 20' wide against a house and out 16'.
grade is 8 inches from the top of the deck. The ground is very tough. lots of hard rock and seems to be very sturdy. I dont want to attach it to the house (permits needed and a PITA)
Does that mean that you don't need permits if you don't attach it to the house?
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Old 11-03-2012, 11:54 AM   #14
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detatched 16x20 deck on piles


Quote:
Originally Posted by Fix'n it View Post
interesting. as i am going to build a deck myself, hopefully next summer.

i also am going to do a floating deck. i was planning on cantilevering it over to the house. perhaps this will work for the OP ? how far is a safe overhang ?
check out the "Prescriptive Residential Wood Deck Construction Guide." it will give you pretty much all the information you need.
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Old 11-03-2012, 12:07 PM   #15
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It depends on your region and town whether you need a permit for a non attached deck or not

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