Deck Pier Footings – How do you do them?
Shoeman
| Posted in Construction Techniques on
Was wondering how different folks do their footings for deck posts.
Bell out bottom of hole?
Use the fiberboard tubes?
Tried the Bigfoot footing system?
Square? Round?
Drill with 2 man auger? Hand dig? Auger on Dingo?
Who does what?
Pro-Deck, you must have a pretty good system – care to share?
I thought it would be nice to use the Bigfoot system as it would allow me to insert tube and backfill and not have to worry about hole filling in while waiting for inspection, but found that they are like 2′ diameter – don’t know that I want to dig that big of hole – 42″ to frost line here – also was supprised that they were $20 each just for the plastic part –
Replies
we dig to a 42" frostline.. bell out the bottom to about 16" dia.... put one sack of Quickcrete in each hole.. two if the hole gets bigger because of rocks or maybe two posts close together..tamp the top of the pour smooth so the post location can be adjusted
then we set our posts .. usually get about 3' of bury.. we like the lateral resistance this gives our posts.. which usually extend to bottom of rail
Mike Smith Rhode Island : Design / Build / Repair / Restore
Mike--
Most wood posts I've ever seen buried have bit the big one much too sooner than later. They don't rot in the ground, they rot at ground level. Aerobic vs anaerobic wood munchers....
I don't really see an issue with lateral support of the post. If the foot of the post is bolted into a bracket bolted in turn to the top of a concrete post, it's not gonna move unless the wood bends--and burying the bottom of the post isn't going to stop that (by the way, I've got to dig down to 60"--I've gotcha by a foot and a half! We use an auger--when we can).
There's another way small decks are supported up here, which is much less elaborate and a hell of a lot cheaper. (Note I wouldn't use this on a 'serious' deck.) You dig an 18" square hole two feet deep and fill it with 3/4 washed gravel, compact it well, and then set what we call an 'elephant foot' on that. This is a six-sided truncated concrete pyramid about 12" square with a recess for a wood post moulded into the top surface. The way this works is, any water or snow melt drains through the gravel before freezing, and most of the ice- heave from the earth under the gravel pit is absorbed by the gravel before it gets to the post. It's not 100%, for sure; the deck may float an inch or so seasonally, which is why you've gotta be careful with your applications. It's practical for some; not acceptable for others.
Just my thoughts....
Dinosaur
'Y-a-tu de la justice dans ce maudit monde?
dino.. so far we've been getting .040 CCA SYP.. since the early '80's.. i have yet to see ONE (1)... one... rot out below grade or at grade....
when i started we couldn't get PT.. we used to pour a concrete column with a truncated pyramid top form with an anchor bolt coming out the top...
now we do it this way.. our soil bearing is in excess of 2000 lb/sf...Mike Smith Rhode Island : Design / Build / Repair / Restore
Mike--
CCA is dead or dying 'most everywhere now, and I for one am glad about it. I can't tell you how many times I've had to convince somebody not to build a play set for their kids to run barefoot on out of it, or a dock sitting in a lake from which they plan on drinking the water, or whatever.
There are natural essences that don't rot easily, I'm sure you know. Red or white cedar are two of the best-known; Hemlock is less known but an excellent rot-resister that I use if the customer doesn't like the cost of cedar.
Still, I don't see the advantage to burying the wood if I've got to pour a footing anyway: why not just pour up to grade and have it done with?
Dinosaur
'Y-a-tu de la justice dans ce maudit monde?
dino... CCA is the greatest thing since sliced bread.. too bad the insurance companies got scared off...
i've worked with ALL the rot resistent species... we spend a good part of every year replacing them where they have rotted off... i've never had to replace PT SYP.. and i don't believe in the health risks...
but then i stopped using it for decking 15 years ago.. it's just an unsuitable material for deckingMike Smith Rhode Island : Design / Build / Repair / Restore
Mike--
With a nickname like 'Dinosaur', I guess you coulda figured I bake my own bread, too--and slice it by hand.
If I could figure out a way to e-mail you a slice, I would, with some homemade wild blueberry jam as an attachment.
Dinosaur
'Y-a-tu de la justice dans ce maudit monde?
send me your snail-mail address and i'll trade you some home made salsa for your jam....Mike Smith Rhode Island : Design / Build / Repair / Restore
Mike:
CCA seems to be on the way out whether we like it or not (December '03, I think.) How confident are you about ACQ not rotting in similar applications? Did I hear that larger dimension lumber (eg. 6x6) will still be available in CCA?
Thanks!
Al Mollitor, Sharon MA
PS: 48" here in Massachusetts. My old back would love to know if someone has an affordable and easy way to dig in bony New England soils!
"Did I hear that larger dimension lumber (eg. 6x6) will still be available in CCA?"
Available for "industrial" usages, whatever that means.
Problem for marine piers and the like.
Doubt if you will be able to get the 6x6 at the local lumber yard.
It's a deal. Real mail on the way by e-mail. You want strawberry or blueberry or raspberry?
Dinosaur
'Y-a-tu de la justice dans ce maudit monde?
I'll vouch for Mikes Salsa, it is very good. I like strawberry freezer jam myself and all I can trade is a Pro-Dek hat.................."Rather be a hammer than a nail"
Bob
We keep this up we'll be getting complaints from E-bay!Dinosaur
'Y-a-tu de la justice dans ce maudit monde?
Thanks for all the responses !
I've done them many different ways over the years - pads, buried post, post connected to concrete with saddle, pretty much everything that has been mentioned, other than the precast. Was thinking with all the ways there are to do it, that it would be interesting to see a discussion. Thanks for that.
I always try to get a footer bigger than the pier. Been raining so much here lately, that I thought it would be nice to try something like the bigfoot, that could be backfilled, yet left empty while I wait for the inspector. Seems like there would be a market for a bigfoot type product that was 12" in diameter at the base, and accepted a 8" tube. Even 18" base would be allright. Preffer nothing larger than 18" as that is about as big an auger as most the rental companies around here rent.
Anyone have experience using a Dingo for drilling holes? I've got one reserved for this Sunday to try out. Have used the trailer mount augers that work something like a teeter totter, but never the Dingo style. Looks like it should be easy on the back.
Thanks again,
Shoe
Oer the years, I've done almost every way youdescribed and then some.
In Mike's picture, I couldn't see the feet very well but it sounds like he's burying the posts, which works good if you wrap them with foam board or a plastic wrap to keep the frost from locking onto them and heaving up.
I've done a lot of piers for houses which need a footing like bigfoot. ( BTW - they now have a competitor that has the tube and the bottm bell foot all in one piece of plastic.) I've also built with forming my own pyramidal pier of plywood form.
If there is any chance that the dcek will turn into a porch ( with roof over) and then a screen room, and then a three season room and then....The potential for adding loads and the need to avoid movement dictates a good footing to bear more than just a deck will do.
But in my mind, the real reason for the bell or footing on these is to avoid frost heaving it out of the ground. I've seen a lot of decks here poured on four foot suana tube piers with nothing else under foot and it seems like one out of every fifteen or twenty piers heaves out of the ground.
Since my back has gone bad, I've taken to doing the digging with a backhoe so size of hole is not a problem. I like the bigfoot ones but I can also get some precast pyramidal piers 4' or five feet tall with a threaded hole for mounting hardware. They are my favorite. smaller hole Fairly accurate placement is necessary. I made up an eyebolt with same threading that I screw into the hole and then hook a chain to it and use the backhoe to swing it over and down in. With a helper to guide it we can seat it right the first or second time.
Excellence is its own reward!
Piff, can you give me any futher information on the company that is doing the one piece, Bigfoot style form?
Thanks in advance,
Shoe
Here you go shoeman- http://bigfootsystems.com/Consumers/"Rather be a hammer than a nail"
Bob
Thanks Pro-Dek,
I have seen that site. I was trying to get info on a Bigfoot competitor that Piffen mentioned in post #3 of this thread. He mentioned that they were making a one piece plastic foot and tube combined. I was curious to find more info on them. Specifically, I would like to know if they make a footer that will fit in a 12" diameter hole. Need to dig about 4' deep here for frost, but are only required to have a 12" pad at the bottom. Can then run a 8" tube up to or above grade. Looked like the smallest footers on the Bigfoot site were maybe 20" diameter. Would rather not have to go that big around as I have to go so deep.
None of it really matters for current job. I will be using a Dingo with a 12" auger to dig holes. Get inspection, then pour about a foot of concrete in bottom of hole, center 8" tube on that, backfill tube, fill tube with concrete about a foot above grade.
Still am interested for ideas for future though. One piece form seems like it would be nice. Especially in cities where it takes a few days to get inspection of holes. Just backfill tube with footer and put a cap on it - don't have to worry about hole filling in or having kids fall in, etc...
Thanks again, Shoe
ps.
Did some footers similar to what you describe when I was living in Alaska. Building on rock and couldn't dig a hole for nothing.
It was just this past week when I stopped in to the yard that the manager/owner asked, " Hey P___, Have you seen the new kind of bogfoot systems we've got?"
I looked at them but didn't get the name brand. I'll have to ask. Remind me if you don't hear back. I think the bases must be about 20" though..
Excellence is its own reward!
Shoe:
I too have done this many ways, but most common around here for decks of 0-1 storey is a 8" sonotube, belled out to 12-14" depending on spacing of piers. (It seems a waste to pour 4' of 12" dia. concrete when you only need the 12" for bearing area on the soil, not for bearing area of the post onto the pier). I like to bring the top 6" above grade and then use a saddle to attach the wood post. In some cases, like the bottom newell post of an exterior stair, I will bury the post for lateral support, but I generally like to keep wood away from dirt. Mike, did the architect call for burying for lateral support in the job shown in the photos?
One detail I don't like is the round sono tube coming out throught the ground or slab or whatever and then transitioning into the square column. I have seen a better detail where a separate square cap was poured above grade and onto which the column was set. That way you don't see any round tube at all, and the column base detail is much cleaner.
Anyone else tried that?
Andy
I'm in the sun belt (18" footer is plenty) and I used a similar detail on my recent project. I set a 8x8 half CMU into the top of the footer a bit, with rebar bent so that it extends up into the bottom of the hole in the block somewhat, with the rest of the bar in the footer. (Ascii representation of rebar: __/__ ) Then I buried the anchor L-bolt so that it hooked onto the rebar, and packed the concrete (monolithic pour) up the hole in the block to tie it all together. The 6x6 PT post sits on the square block and is anchored via a Simpson post base. The concrete is hardly noticeable beneath the post.
I liked this because the sharp corners of the half block line up more appealingly with the post and the post is kept away from the dirt and concrete by the Simpson standoff anchor. Termites and rot are known to affect PT eventually around here.
Forming a square top is another way to go... some kind of square prefab form would make this easy.
Unfortunately I don't have a picture handy but I think you get the idea.
I live in a pretty serious seismic zone so we usually need a permit and engineering for even the smallest decks. Snow load is also a concern. My typical pier looks in x-section like an upside down T. The pad is usually 18" to 36" square and about 10" to 12" thick. The riser is a sonotube uaually, 12" diameter. For a 42" depth the sonotube would be 36" high to be 6" above grade. The pier also has lots of steel in the form of a grid in the footing and risers and stirrups in the tube. I build a support for the sonotube at grade and fill the pier in one pour. I install the steel risers and stirrups as the tube is filled. A post base or a column base is specced by the engineer. Precast piers don't fly here. They don't prevent uplift in case of a quake. The tricky part is building the support for the sonotube. I build an H shaped support out of 2x4s and stake it to the ground. I nail the top of the tube from the inside to the support.
Our ground around here is more rock than dirt. We dig a 2'x2'x8" hole throw in a bag of premix, set a pier block with a 4" adjustable saddle on top of the dry premix, level and line all the pier blocks, if we can we put a 2x4 in the saddles to line up the blocks, then we add a second bag of premix to each hole.
This makes for a nice wide footing.
If the deck is on a hill we are required to dig to China and place a footing with rebar and a Sono tube 2' above the grade.
"Rather be a hammer than a nail"
Bob
I have a question post somewhere over here, but this seems like a good place for it too,,have any of you guys tried plastic deck footings,,,www.redifooting.com ? Page 36, November issue, Mike Guertin has been using them for a while,,27,000 lb load capacity, all sorts of testing done with the paper to prove it,,he has to go down 40'' in RI, just did the hole,place the footing, backfill,,bang bang done,,,John Hyatt deckmastersllc.com