Thread: Porch post footings

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Originally Posted by RobertSmith

Do you guys make any comment regarding the block footings that the posts are installed into for porch, decks?

Do-it-yourself job for sure, and un-permitted too (at least I know of no proper footing which is allowed to be "on" the soil like those things are).

Also, should not the end of the 2x rim board be over the post for support?

I'd be more concerned about the most-likely-un-permitted porch addition to which that goes ... that lap 'could' be okay if the post is under both sections of the double beam (it's a beam, not a rim joist), however, I suspect that the back piece is simply nailed to the post and not on the post.

Looks like they had the wrong guy on the smart end of the plumb bob for that beam install!!

Originally Posted by Jerry Peck

Do-it-yourself job for sure, and un-permitted too (at least I know of no proper footing which is allowed to be "on" the soil like those things are)...

There is at least one brand of manufactured "floating" deck footings, but they are intended only for use with free standing decks (in which case they meet 2006 IRC R403.1.4.1 exception 3), and "Doze ain't dem'."

Originally Posted by Michael Thomas

There is at least one brand of manufactured "floating" deck footings, but they are intended only for use with free standing decks (in which case they meet 2006 IRC R403.1.4.1 exception 3), and "Doze ain't dem'."

Huh?

From the IRC. (bold and underlining are mine)

- R403.1.4 Minimum depth.

All exterior footings shall be placed at least 12 inches (305 mm) below the undisturbed ground surface. Where applicable, the depth of footings shall also conform to Sections R403.1.4.1 through R403.1.4.2.

- - R403.1.4.1 Frost protection.

Except where otherwise protected from frost, foundation walls, piers and other permanent supports of buildings and structures shall be protected from frost by one or more of the following methods:
- - - 1. Extended below the frost line specified in Table R301.2.(1);
- - - 2. Constructing in accordance with Section R403.3;
- - - 3. Constructing in accordance with ASCE 32; or
- - - 4. Erected on solid rock.

- - - Exceptions: (Jerry's note: These exceptions are exceptions to "Frost Protection".)

- - - - 1. Protection of freestanding accessory structures with an area of 600 square feet (56 m

2) or less, of light-framed construction, with an eave height of 10 feet (3048 mm) or less shall not be required.
- - - - 2. Protection of freestanding accessory structures with an area of 400 square feet (37m2) or less, of other than light-framed construction, with an eave height of 10 feet (3048 mm) or less shall not be required.
- - - - 3. Decks not supported by a dwelling need not be provided with footings that extend below the frost line.

Notice that the exceptions apply to "R403.1.4.1 Frost protection.", not to "R403.1.4 Minimum depth.".

Thus, the minimum footing depth is "at least 12 inches (305 mm) below the undisturbed ground surface".

I have not seen any of those footings which are designed sufficiently large enough to extend "at least 12 inches (305 mm) below the undisturbed ground surface".

You are correct in that free standing decks do not need to be protected from frost.

Jerry,

I'm trying to remember who makes them... "it's on he tip of my brain". The system is a disk about 18" or 20" across, which is centered on a hand-driven post which prevents lateral movement only (the post is not load bearing). The major limitation is finding areas that a AHJ will accept as "undisturbed soil" in backfilled areas for the first few years after construction.

Originally Posted by Michael Thomas

The system is a disk about 18" or 20" across, which is centered on a hand-driven post which prevents lateral movement only (the post is not load bearing).

Scratching my head trying to visualize that ...

What size and length "post" under the disk?

If the post is not load bearing, then the "disk" is, which makes the disk the footing, which mean it must be 12" below undisturbed earth, with that "post" below it. Now, though, that disk must meet the requirements for footings. If that disk is an "engineered" "footing", then the soil bearing capacity would need to be "known", which would require soil bearing tests at each disk location.

I am visualizing that as a disk on a post, tipping around with any eccentrically loaded load, which would be 'not good'.

He ya' go: could not find the one I've seen, but here is a similar system:

Basic Info: OZ-POST Instant Post Holes
FAQ OZ-POST Instant Post Holes

(I see the argument coming up here ... no need to fight it with me, it's with the AHJs.)

(underlining is mine)
"Oz-Deck meets ICC (International Code Council) IRC-2006 (International Residential Code For One- And Two-Family Dwellings 2006) 2006 IRC, R403.1.4.1 exception 3 where it states, ‘decks not supported by a dwelling need not be provided with footings that extend below the frost line.’ The building code clearly has provisions for floating deck systems like Oz-Deck."

They too are mis-reading the IRC - see my post above.

Their square base becomes the footing, which is required to be at least 12" below undisturbed earth ... and those are placed 'on' the earth.

I glanced through all their stuff and do not find anything which *states* that they are approved for use. They simply state "The building code clearly has provisions for floating deck systems ... ", except that they are wrong.

I also searched the ICC Evaluation Reports and came up with "No report matched your search terms.", so I scrolled through the complete list of Evaluation Reports and still did not find them.

I don't see any listing for them being approved for use, *they* don't even say they are approved for use (only that the "code clearly" allows their product), to me ... this means they are "clearly" *NOT* approved for use.

Originally Posted by Jerry Peck

"Oz-Deck
I don't see any listing for them being approved for use,

They are listed and approved at the BIG BOX with COLOR Brochures and drawings and diagrams and everything.