Footing Size for Lally Columns

[Otis P. Driftwood]

Replacing a number of lally columns in an 1870's farmhouse next month, and need opinions on the footings. I'm using 4" steel/cement lally columns, and from past jobs I pour rebar reinforced footings measuring 24x24x12.

The client who has a relative in the masonry field, feels it's "extreme" and smaller footings measuring 12x12x6 would be ok. My philosophy has been to 'overbuild' things to exceed code and add a measure of safety.

J

[MarkMc]

Re: Footing Size for Lally Columns

12x12x6 would be ok to hold that 4" pipe up in an interior application; does it need to help hold up the house too? If so, how much and what it's on, is more important than how old. The smaller size could be fine depending, the larger in most cases, would always work and add relatively little in added cost.

[James Eggert]

Re: Footing Size for Lally Columns

There are two issues at play here, bearing size of the pad, and thickness of the pad.

The 24x24 is 4x the bearing size of the 12x12, and very typically are specified for all sorts of pier installations.

Who wants to say how much vertical force a 6" thick pad can handle before failing versus once again what could be considered the norm of the industry, 12" thick?

Because we don't know what you are holding up, is the mason taking on the liability of specifying the foundation pier? Didn't think so!!!!

Use the 24 x 24 setup!

[Joe Carola]

Re: Footing Size for Lally Columns

Replacing a number of lally columns in an 1870's farmhouse next month, and need opinions on the footings. I'm using 4" steel/cement lally columns, and from past jobs I pour rebar reinforced footings measuring 24x24x12.

The client who has a relative in the masonry field, feels it's "extreme" and smaller footings measuring 12x12x6 would be ok. My philosophy has been to 'overbuild' things to exceed code and add a measure of safety.

J

Who says your overbuilding? Who cares what the relatives mason says also, he's not doing it. Screw him! Every footing around here is 24x24x12. Ask your inspector what you need. If he doesn't give you an answer go with what YOU want anyway.

[TSJHD1]

Re: Footing Size for Lally Columns

12x12x6 would be ok to hold that 4" pipe up in an interior application;

How can you make that statement w/o knowing what load the column is carrying? You can't.

To the OP: You need to determine the load those columns will be carrying and the soil's bearing capacity to properly size the footings. It's too important a detail to guess. Pier footings that carry a concentrated load need to be thick. Slabs are poured 4-6 inches thick, and they get thickened to at least 12" where they carry a bearing wall, which is a line load, not concentrated.

Spend some $$ and get those footings sized by an engineer.

Tom

[MarkMc]

Re: Footing Size for Lally Columns

How can you make that statement w/o knowing what load the column is carrying? You can't.

To the OP: You need to determine the load those columns will be carrying and the soil's bearing capacity to properly size the footings. It's too important a detail to guess. Pier footings that carry a concentrated load need to be thick. Slabs are poured 4-6 inches thick, and they get thickened to at least 12" where they carry a bearing wall, which is a line load, not concentrated.

Spend some $$ and get those footings sized by an engineer.

Tom

Tom, read the full sentence..."does it need to help hold up the house too?".

But you are correct, I can't, based on the info provided, and I didn't.

[Top Notch]

Re: Footing Size for Lally Columns

UNLESS you pull apart the live and dead tributary loading of the that post there is no way anyone can help you. I would say 12" deep minimum and the 24 " x 24' is the way to go. ( say you have 1sqft of support for a bad soil type of 1200lbs /sf---doubling the size to 2x2 doesnt equal 2400lbs its 4 sqft x 1200 so 4800 lbs)Likely over done for most residential homes with a basic layout but we cant guess what your holding.

[TSJHD1]

Re: Footing Size for Lally Columns

Tom, read the full sentence..."does it need to help hold up the house too?".

But you are correct, I can't, based on the info provided, and I didn't.

I read the full sentence! But the way you wrote it completed the thought at the semicolon.

Tom

[MarkMc]

Re: Footing Size for Lally Columns

Which was that the baby footing was big enough to hold the pipe - not a column or post, indoors and protected. Following the dotted comma it then went on to ask about the need for supporting the house.

Give without remembering; take without forgetting.

[Timbersmith]

Re: Footing Size for Lally Columns

You need an engineer. Unless the client is an engineer, he has very little useful input. No professional would size footing by looking big enough.

[George Roberts]

Re: Footing Size for Lally Columns

One can look up the failure load of the lally column and compute the footing size from that.

14000 pounds seems like reasonable failure load. About 7 square foot of footing. About 31"x31"x16".

[Otis P. Driftwood]

Re: Footing Size for Lally Columns

Who says your overbuilding? Who cares what the relatives mason says also, he's not doing it. Screw him! Every footing around here is 24x24x12. Ask your inspector what you need. If he doesn't give you an answer go with what YOU want anyway.

The BI agreed that the size of the footings (24x24x12) I spec'd out is the way to go, in spite of the client's "disagreement". Another case of a client looking to cut costs, which I'm seeing a lot of these days....

Issue closed