Continuous footing VS individual footing
Hi All,
I have someone new for the foundation of my old house who wants to form the piers and pour, no block. I was thinking the continuous footing may be better instead of individual footings, any thoughts?
Thanks
Kevin
Replies
they are basiclly the same. to hold a load. But what does the foundation engineer say.
He originally ok'd the individual pier on individual footing idea, I just saw the continuous footing on the web with the piers and thought it would be a good idea, seemed stronger. I'd have to run it by him and get sealed drawings, just not sure if it's overkill. More work and money than I need to spend. I'll post a link to pictures of the cottage.http://acx.prospero.com/dir-app/icon.aspx?realmId=76&iconTypeId=4&iconName=attach_logo
Edited 2/23/2007 11:07 pm ET by dockelly
Kevin, when you say "piers" do you mean like "sonotubes" spaced every 4 ft. or so? I run into this all the time when I price additions. Everybody thinks they can take down there old decks and re-use the same footing piers to build on, until I give them the bad news......
Even though it's more work, I would stick with the continuous footing. The code book states: "All exterior walls required to be supported on continuous footings". Were you planning on making exterior walls?
Sure, you can do individual "piers" like sonotubes and install some type of girder system to support the new structure, like a small addition, but there's two drawbacks to that:
1) You're inspector will want you to pay someone to properly size that girder to insure that it can support the load. This means hiring an architect or structual engineer to draw up plans and you're talking BIG BIG BUCKS for that stuff, like 2K-3K (that's no lie)
2)Second drawback is that you're new structure will be very bouncy. What you end up doing is creating a "deck". Have you ever noticed all the bounce (deflection) you get when you walk on a deck? Plus the room will be harder to heat.
Mike
Yes and no. The guy doing the work would use plywood forms, 2'x2'x1'high footing with a 16"x16" poured pier with rebar. I just thought connecting all the footing would make for a better job. Just not sure if it's necessary.
The code book states: "All exterior walls required to be supported on continuous footings". Were you planning on making exterior walls?
What code book is that?
Code Check Building - A Field Guide to the Building Codes. Page 3 left hand column.
I just noticed that it was published in 2003. What are the chances that the code has changed since then regarding continuous footings? Next time I'm in Depot I'll open a current field guide and check to see if that requirement is still the same. Who knows, maybe it changed.
Mike
Depends on the location and what the ground is like.
location is one block from the ocean with a high water table. I know the engineer would have the final word as to wether the site would permit this. My question is wether or not there is any advantage to continuous vs. single footing, assuming soil would tolerate load.
You're a doctor, so lemmee ask you:
Is there an advantage to using a butterfly bandage instead of stitches?
Oh! You say they are used for different conditions?
So are simple footings, spread footings, thickened edge, piers, and pier and beam footings.
Ask your soils engineer if piers would be right for you. ;)SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
SamI've gotta confess I didn't think this was such a complicated question. Engineer said the pier on single footing would work, sealed the drawings for same. The house lifter questioned why I wasn't going with full foundation and said that's how he would do it. I just saw it done the other way and it got me thinking, a compromise between the two.thanks
KevinPS I'm a chiropractor, don't use bandages or stiches :)
so your house lifter has an engineering degree, I guess on weekend he works at Home depot. I know he stayed in a Holiday Inn.
not like that BB, he mentioned it during our conversation as a suggestion is all. One of the nicest guys you could hope to meet, his wife does all the secretarial stuff. They are, hands down, the two best people I have had to deal with throughout this whole process. He was saying that it would be more bullet proof, that if the piers eventually failed I'd have to lift the house a second time. His reasoning was why not do it thjat way the first time. Just two guys talking really.
my point is this, An engineering firm is never wrong, even if you think they are, they are not. Alot of libelity ride on the engineer. If it fails, the engineer get sued, not the house lifter. So they must be a reason that they wanted piers. You should of told the house lifter. "Because they say so"
point taken but I still think your reading too much into his comment, just talk between two guys.
Here's a reason to use a continuous footing along with the spaced piers you are contemplating.
Many structures on piers are required to have some form of skirting between the piers for asthetic and pest control. The footing provides a firm base for almost anything you could envision.
Wasn't there a recent discussion about this very thing?
Now, your house movers suggestion of a continuous foundation is not, as I read it, the same as the continuous footing you are questioning. He would prefer the continuous footing, topped by a stem wall as continuous solid support under the rim rather than individual piers spaced to support the loading, as you are contemplating. Si?
How is your house structure currently supported? If you are presently on piers you should already have the girder structure to handle a new pier foundation. If you are not, then that would be a necessary retrofit.
In addition, houses on piers are not just supported by perimeter piers but on intermediate piers spaced beneath the house. If you go with a continuous perimeter foundation as is suggested by your house mover then you must also still take into account the absolutely necessary supports under the rest of the house. Will that be another full stem wall in one or more lines of support?
Since it appears you are moving an existing structure to a new resting place, one block from the beach, one of the parameters should be the probability of storm surge reaching and undermining your foundation or tossing your house off the piers or stem wall.
Also to be considered is the potential high water mark which will affect the actual sill height of the house. Friends of ours have a house on piers in Carolina Beach, NC, and had to deal with water damage to about 4 feet above the floor. The piers, on individual pads, held up just fine.
In Bridgewater, NJ, where my brother lives, the same thing happened when the river swamped the town. Many of the buildings there have now been raised maybe 8 feet or more to accomodate future flooding.
With a non-scouring type of flooding, individual footing pads will do just fine, as will full footings.
If there is a severe enough potential for the land to waste away around your house then pilings rather than piers would make more sense. Ocean piers are actually platforms on pilings. Most of the time they stay put.
A benefit of pilings, driven or cast in place is almost a whole house footprint, with the house raised high enough, for extra parking and storage beneath as well as no wet interior should a big blow hit the area.
Now that we've considered spending your next 5 years income...
Edited 2/25/2007 10:21 pm ET by RalphWicklund
"Now that we've considered spending your next 5 years income..."Boy that's a mouthfull! Your right about a full stem wall, that's what he suggested. Virtually the same as current day construction. I just wanted to get some feedback from the guys here. There will be piers under the house as well, same design, and they would not have a continous footing."Since it appears you are moving an existing structure to a new resting place, one block from the beach, one of the parameters should be the probability of storm surge reaching and undermining your foundation or tossing your house off the piers or stem wall."Only thing you got wrong, house is already there. All I'm doing is raising it 32".Here are some pictures, the link I had posted earlier in the link does not seem to be opening.http://forums.taunton.com/n/mb/message.asp?webtag=tp-breaktime&msg=69253.8
Edited 2/25/2007 11:02 pm ET by dockelly
Kevin,
I just reread all your posts through the entire thread. And this is my final say.
The engineers pier and footing is better. I would want as deep a footing as I could get.
I personally prefer a continuous foundation provided Surge Wave action is not a factor.
SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Edited 2/25/2007 11:33 pm by SamT
Edited 2/25/2007 11:34 pm by SamT
Edited 2/25/2007 11:37 pm by SamT
Thanks for the reply. AHJ? Authority having jurisdiction?
right
BTW, reread that post.
SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Edited 2/25/2007 11:53 pm by SamT
I reread it, lots of edits. Hope I didn't give you a headache:)
Thar's many ways to skin a catfish.
I was stationed in Exmouth, Northwest Cape, west Australia for a while. The houses there were built to withstand 160mph winds and 12"/hour rain at the same time.
The Yank housing was Slab on Foundation on Footing with solid filled CMU walls, concrete roof, and heeevy duty 12ga aluminum awning/shutters and steel doors.
The Ausies' sank concrete anchor pins with eye rods poking out the top. Then they connected a 3D pyramidal matrix of 1" tubing to those and built on top of the matrix.
Looked like they was sitting on 4' long bicycle spokes.SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Now that I understand the question better -
I can't really say wheether one is better than the other for you. It would depend on your soil/water conditions. I assume sandy with regularly rising and falling groundwater.One of the houses here I rebuilt was originally done on separate piers. It was in clay type soil on approx, a 10% slope. Over a hundred years some of the individual footings had moved three inches downslope relative to others, and as much as five inches horizontally. This was due to water moving through the sols on the slope primarily.So when we rebuilt it, we used continuos footers. Then in some places there were full steem walls and in others there were piers rising from the footers. The contimnuopus footer wasintended to anchor and tie things together. it has only been about fifteen years so I can't say whether it will do better or not yet.
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Piles are used to support heavy bridges. A continuous footing may be used to support skyscrapers. What you do largely depends on the soil conditions closer to the surface. The answer to your question depends on a number of variables.
You have posted enough here that I have some vague memories o the house. It is in a flood zone right?
That means you have to keep that underspace free in some locations for water to paass in and out which leaves you with a pier type foundationsam worded it all best.
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It would still be piers, just set on a continous footing.