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Float new deck footings or?

Posted: Wed Apr 22, 2020 1:58 pm
by mdnagel
Note: "on-grade" is what I mean when I say "float."

I'm continuing to pursue my re-deck project. Planning on replacing our current deck with a similar sized one (replacement will include a patio/covering part of the deck- the details for the roof construction still elude me, so in the name of getting myself out of my analysis paralysis over that I'll look to build with requisite posts and do the roof part when it all comes clear to me).

My current conundrum has to do with footings.

Existing deck has posts that, next to the house, sit on the house's monolithic pad (about 1' of the pad extends out past the house), while all other posts sit on concrete blocks (trapezoidal type) that sit on top of the ground. I can't help but think that there's a float difference between the posts on the monolithic slab vs those on their individual blocks.

Frost level is really shallow: high water table and mild winters here. No idea on soil stability under slab compared to surroundings. All was done a good 20 years ago (about 10 years before I bought the place).

Is it advisable to look to continue to use the monolithic pad (for the posts next to the house), or should I look to make ALL post footings totally independent (and if so, float or buried)?

I've got a septic line running out from this area and worry about digging, about whether a necessary footing location ends up running into that line. Above ground/float would eliminate this concern, but I would like to aim for doing the structurally correct thing.

Re: Float new deck footings or?

Posted: Wed Apr 22, 2020 3:57 pm
by Greg
My first thought is if it has been working for you why change it?
I would say code may require below frost line footers (posts) but you would have to check on that.


Re: Float new deck footings or?

Posted: Wed Apr 22, 2020 4:13 pm
by mdnagel
The existing deck is nearing end of life. It's old and in need of replacing. I would NOT go by anything that was done here previously: most certainly not the worst, but in no means the best.

Below-grade footings are generally the better way to go. In this case, though, I'm looking at dissimilar footings vis a vis the home and the deck. The current deck is floating on two different supports and I feel like this just isn't right. If I wasn't looking to put up a roof on part of the deck (and needing to mate up with the house's roof) I wouldn't care so much: with a roof structure differences will show up being more pronounced. I know that there's going to be some sort of difference, but I am unsure which affords the least amount of difference. The over-sizing of the pad has been one big annoyance to/for me.