Decks, Patios, Porches and Docks - Shallow post holes - HELP!!!

A family member was nice enough to build our deck for us..unfortunately, he dug the holes only 24" - our local frostline is 36" Is there anything I can do NOW (after the deck is built) to reduce the risk of Frost heave???

Could I place any fill above the deck area to raise the grade? Could I place anything above the area to insulate the area or help in drainage??

Thanks for your help - the deck is beautiful - I want to save it before the winter comes!

I can't think of any shortcuts to solve your problem. Did he install concrete piers to support the 4x4 deck posts? To do it right, I'd probably redig the holes to the proper depth. You would need a temporary support to hold the deck up. If it's a concrete pier, you'd need to remove it and rebuild a new one.

The posts are PT 4x4s embedded in concrete. Another problem, but I'm more comfortable with premature rot than frost heave.

Since i'm already at risk w/ the embedded posts, what would happen if filled 12" above the concrete? The fill against the PT post should be less of a concern than the frost heave right? and the added fill would in effect raise the grade...?

I don't think adding concrete above the grade line will in effect raise the grade. Any water in the ground below your 24" that freezes will give you the frost heave you're worried about.

If you're really concerned about this, then the correct way to go would be what RichD suggested, support the area of the post you're working on, dig down under the footing the depth you need to go and pour concrete. You could do this one or two a week and be done in no time I'm sure. At least this way you'll know it's done properly.

I always use high strength concrete mix as well, 5000psi. Well worth the extra buck or so per 80lb bag.

By the way, how old is the deck and how high off the ground is it?

I built a grade level deck 4 years ago, put footings in about 2 feet or so and have never had a problem, and I live in Massachusetts.

I wasn't talking about adding CONCRETE above the grade. I was considering adding some sort of soil or sand or gravel or a combination...something to backfill ABOVE the current grade to help insulate the area where the footings are.

More info on the deck: it is about 500 sq. feet. The highest section of the deck is about 4 feet high, the lowest section (the ground slopes below it) is about 1 foot high. The joists are attached directly to the posts (no beams),so I am apprehensive about trying to replace them..sounds like a MAJOR job.
It is a FREE-standing deck built next to the house (so at least It shouldn't damage my foundation!)..I'm just concerned about it going out of square/level/plumb or moving away from the house...or pushing up on the house and damaging siding, etc.

Not knowing much about frost heave, how much movement might I expect?

I live in Eastern PA...The deck is only a few weeks old...I don't have any practical experience with frost lines...just going on what the local codes in the area are (most say 36). Is anyone in the eastern PA area? I'm about an hour north of philly - what has your frost depth experience been? How much risk/danger am I really in?? My wife, by the way thinks I'm overly concerned - I think she's foolishly optimistic ;)

i wouldnt worry..i live in pittsburgh PA... ive built my share of decks and such... only the ones that had to be inspected can i guarantee were dug down and flared base to 36 inches. PA is horrid soil even with a post hole auger just too rocky. if the deck is free standing then any movement should be uniform ie no twisting of ledger etc.. id say relax sit on the deck ...but do learn from it.. one thing i can say the more i build the better my next project will be lol :)


Hope this helps--Josh

Hi,

You should relax because of one thing....it is freestanding and the posts are 24"

In my area, that is the code for a freestanding deck----and I live in the south suburbs of Chicago where it gets 0 degrees every year!

You might have some problems if it was attached to your house. But it is freestanding. Sounds like a beautiful deck.

I would just relax pull out a recliner and bask in the sun before the winter comes.

By the way, you cannot change the frost line by raising the grade.

Spencer

You should be ok.

I live in Maine and I haven't had either of the two decks I've built move yet. The first one was built in '95 (4 x 4 PT down to 2 - 3 ft). Number two is waiting for it's first Maine winter but I went with concrete frost post (4 footers) set at 2-3 ft as well. It was just too rocky to go deeper than that even with an auger.

The code here says 48" frost lines are the norm, but It rarely stays cold enough long enough for that deep of a frost line to form. Both are attached btw.

Thank you all for your input...I feel much more relaxed...sure, I'd rather the holes be deeper, but it sounds like the 36 inches is a bit extreme....I can only hope that global warming continues :)