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Footings for patio deck - concrete block or concrete tube forms, height of deck and codes

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St. John's
12/11/2012 at 12:42:18 PM

Hi,

We have a new patio deck, about 7 feet off the groud, 10x10....the posts were put into concrete patio deck blocks...we have found the patio is now shfting and wobbly.

I'm wondering what the canadian building codes are for decks built a certain height off the ground and/or size.....blocks of contrete forms into the ground?

Thanks

REPLIES (10)
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Jackson Builders in Winnipeg
Date/Time12/11/2012 at 1:08:48 PM

Any attached deck should be set with concrete piles as a footing for the deck.

Frost often causes decks or anything for that matter to heave, throwing everything out of wack.

You could insulate each pad with SM, your best bet would be to have 4 foot concrete piles poured for each post.

Good luck

JB

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John from JALS Corporation in Welland
Date/Time12/11/2012 at 1:15:21 PM

First of all it depends on where you live. The building code is set by the province and inforced by the municipality.

Any deck that is built any where should have the proper foundation at seven ft off the ground. You should be using 6x6 pressure treated lumber anchored into the ground with concrete. It should also have cross bracing connecting the post together which will stop the swaying of the deck.

I would suggest you contact your local building department they are more than happy to help you with any concern.

Regards

John Schertzing

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Date/Time12/11/2012 at 1:20:07 PM

When building a deck that high of the ground we always use 24" big feet followed by 12" sono tubes @ 4'6" deep install saddle brackets then 6X6 posts.

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Date/Time12/11/2012 at 1:39:49 PM

Any deck should have proper concrete foundations. But code changes slightly in different parts of the province.

The type of substrate or soil you are building on effects it as well. To be on the safe side I always dig four feet deep and fill proper P.S.I. concrete, not the garbage you pour in the hole and then add water. But pre-mixed concrete. If the number of holes justifies it, along with other pours on my site, I am inclined to use the concrete from the truck. 3500 P.S.I aerated.

The top foot of the hole should have a sono tube installed as you fill the hole. That will give you a clean and level surface. Then push the saddle brace into the center of each pour. Check them for level. And please, use braces for 6"x6" posts.

When you are framing the deck, you simply Y-brace off of the 6"x6" posts to the 2"x12" beams you should be using for a deck that high off the ground. A deck near the ground can be safely built with 2"x8" boards.

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Date/Time12/11/2012 at 2:33:47 PM

For a 10x10 deck the holes should have been dug minimum 48". In the span and width dimensions at 8 ft out from the house 3 holes should have been dug 48" with 10" sona tube being used in 54" length and left 6" above grade and put the metal saddle for 6x6 post levelled and each hole 3ft to centre on each hole so that your beam lines up correctly and is strapped with a metal plate back & front.

Concrete from a truck lafarge 35 mpa and 6% air is to be used. You must comply with codes even if the deck is under 108 sq ft.

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Sean in St. John's
Date/Time12/11/2012 at 2:40:21 PM

Thanks for all your replies.

There are cross braces (diagonal), deck is not attached to house. Looks like the contractor did a quick one.

It started out nice, but now with the frost and all the rain......I have to check local codes, but even with my lack of knowledge, a deck shouldn't jiggle when you walk on it. Mind you it's not in danger of falling over but is shfting some....but I would has at least used sona tubes....I even found that the end post of the stairs where it touches the ground has NO block under it...I got curious and dug down, it goes down about 14 inches and then ends...what a crock.

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Date/Time12/11/2012 at 5:18:27 PM

I'm not sure what areas you are in, but if you have had issues with frost movement I would recommend replacing the deck blocks with helical piles which are guaranteed against frost movement.

It also sounds like it is as much a bracing issue as anything else.

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Date/Time12/11/2012 at 6:02:54 PM

Sean,

As mentioned by almost all others, provincial codes apply. In some cases if the deck is not attached the the structure, the type of foundation can vary. Having said that, the height is also a factor so the deck block are very probably not acceptable. The depth of the pilings also depends on the depth of frost in your area.

Best to contact your county office who can provide you with local information. If they can't, as in my case, they contract out to an inspection company, ... who do have the answers you want. The information is free.

Good luck.

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Date/Time12/11/2012 at 9:32:18 PM

A deck should never "jiggle". Please DO NOT USE your deck untill it is repaired. You might not think so but it could collapse and you proably won't have any warning.

That being said, hopefully the rest of the deck is built correctly, so that you can have the posts replaced with proper ones set in concrete footings. But if your contractor built it on deck blocks in the first place, it's doubtfull any part of the deck can be saved. Ask your building department if they will come out and look at the deck, to see what is required to fix it.

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Kerry from Tucks Contracting in Calgary
Date/Time12/16/2012 at 8:33:30 PM

The posts upon which the deck sits, requires footings/piles to be set a min of 48 " deep. Pile should be a min of 10" dia, with re-enforcement ( rebar ) for this height. Normally I use 6x6 posts for any thing over 6 feet in height, but could us 6x4's at a minimum, 4x4's are a poor choice and should not be used at this height.

Make sure you deck is properly attached to the house, that usually means it is lagged in and not just screwed/nailed in. And make sure your support beam is tripled up, and glued together. Beam should not be less that 8x8, preference would be 10x10 for this height.

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