Hi everyone – I’m new to Breaktime, but have been reading FH for a number of years and really appreciate the professional approach and attitudes of the contributors and of the folks using this forum. We’re in the middle of Wyoming, and the relatively uncompetitive construction business can make it a challenge to get results as described in the magazine.
Anyway, I’m getting bids for a 21×30 low level redwood deck, and one of the contractors proposes using a footing technique I’ve never heard of, and wonder if it’s an acceptable one. He would dig a 4 ft. deep hole for a 12 in. sonotube, place some gravel at the bottom, place a 6″ or 8″ sonotube in the middle, and then drop a redwood 4×4 into the inner tube. He’d then fill the inner tube with concrete, letting it fill and overflow into the larger outer tube until it is about half full (I assume the outer 12″ tube is only in the lower 2 ft. of the hole). He’d then backfill the holes, leaving the inner concrete w/4×4 an inch or two above grade. After all are installed, the beams would be lagged into the 4x4s and they’d be cut to proper height.
Thanks for any comments/suggestions!
Replies
Gwindoze,
First of all, welcome. I hope you will stay a while and actively participate in the forum.
As for the footing, what you contractor has proposed will work just fine. I'm assuming the 8" sonotube is held 12" short of the bottom to avoid a bond break in the concrete. I assume he wants to use a spread footing for compaction purposes.
Can you tell us a little more about the deck design? Post layout and beams?
dl
I guess your scooping it out to 4' with a backhoe. But why the tube inside a tube ? does it protect the red wood or somthing? wii that inner tube be encapsulated in concrete?
I have worked on a job using sonotubes in sandy soil we kept the bottom up a few inches so the concrete would form a foot. It gives it more roots I guess, and or a snoweshoe effect. but why the tube inside.
To protect the wood? Is it reinforced? where is this job and what kind of load are you planning on?
Thanks everyone for your input. More info on your questions below.
I'll mention holding the 8" tube off of bottom.
He's going to use a power auger for the holes. I think he uses an inner tube because the outer larger tube is only half-height (to save concrete?), so the inner tube helps support the upper part of the 4x4 (from 2 ft. down up to the surface).
I don't have the bid or layout yet, but his rough sketch looked like rows of footings about 5 ft. apart. Spacing along the rows might have been 6 or 8 feet. The joists would span the 5 ft., which seems like it would provide a real stout structure.
We have an L-shaped ranch, and the deck is filling in the open space in the L, so the long dimension is parallel to the long direction of the house. We'll step down one step off of an existing 16x9enclosed deck onto this new deck. No hot tub or anything, just one square hole for an existing tree. Normal partying/grilling is what we'll use it for, and to sit out and watch the stars on our great Wyoming evenings (summer only!).
Thanks again!
Whoa Cowboy!
There is a product called 'Bigfoot' which is a plastic dome that you can set and fit the sonotube right into. Not recommending it over the double tube as long as his concrete is connected. With the cardboard separating the two there is no purpose to the outer one really. There are also precast concrete peirs 4 and 5 feet tall that you can set into a hole with a loader or a big man or two. We used to frame a small footing box to set the sonotube to. All of these follow the same concept. When the moisture in the ground freezes, it forms a lense that exerts pressure up and down both while the frost expands the lense. If the base is larger than the top then the expanding lense will exert greater pressure down than up on the unit so it won't lift out of the ground, even if the total frost depth is slightly deeper some years.
Putting the stone in the bottom of the hole is good, if he packs it, otherwise the weight of the structure will compact it later and it will settle.
but the place where he loses me is putting the 4x4 post down into the concrete tube. There is an abundance of kinds of hardware for attaching posts to bases, much of it adjustable for accurate placement after the concrete cures. Redwood is not as cheap as concrete either. But my main reason is the multitude of times that I have seen installations like this with the concrete shell split apart around the wood and the wood rotten inside the concrete. It's easy to do but not right in my book. I need to estimate replacing one like that this week for a gazeebo that is less than thirty years old.
What happens is that water will follow the wood into the concrete and swell the wood. Then maybe it dries again. Let that happen a few times and the wood is bruised along its perimeter and doesn't fit tight anymore so the gap between wood and concrete is larger and lets more water in. Now winter comes on and that water freezes. There's no metal rewire or bar holding the thin shell of concrete in place so eventually, it breaks.
Now what have you got?
I'm going to suyppose that his reply might be some of the following:
This is a different soils and climate than Maine so your theory dowsn't hold water here.
The redwood won't rot because, well, it's redwood.
The wood goes into the hole first and sets tight down on the stone so that any water will drain all the way down to the stone and go away.
Maybe...Excellence is its own reward!
Sounds fine but I hope he uses the 8" sonotube because a 4x4 barely fits inside 6"! Welcome to Breaktime!
Al
Edited 8/1/2002 4:24:06 AM ET by RAY5111
Thanks Ray. We've got pretty good sand, as we're just off the North Platte River a bit. Our side of town just doesn't get any drywall cracks at door headers, etc. Great for foundations.
I'm not sure I'd encase any wood but ptyp in concrete. Definately not cedar. Ptyp rated for ground contact performs better below grade than above that's for sure.Tom
North Platte River doesn't ring a bell. you might look into getting a water level. this cheap tool, avail. almost all tool stores and http://www. about 30 bucks accurate to 1/8" over 100'. very easy learning curve. goes around corners!!! just drag the lenght of 1/4" tubing and mark. one hint keep the marking end above the main water supply. keep the bubbles out of the tubing, don't store in the sun.
good luck
[email protected]
Depending on your design and deck height, in a case where appearance maybe a factor. Run the pier's right up to the suporting beam. Eliminate the post. If you must use a post. What we would do is use a driftpin. If the pier is stable, And you are not planning to build a three story apartment building, over the deck. the pins should keep it stable while alowing the post to get the air it needs to keep from rotting.
After you have established your pier/ sono tube hieght, add your re- rod and pour. Whether you are using a post, or a beam, on the top of the pier, pitch the top of the pier. Do this so the water sheds off the sides. Like a cone top, with a platau for the member to rest.
Better still, Simpson makes a fastener with ears that mount in the concrete. It keeps it up off the concrete, so it will get air. That might work even better.
The trick in all of this obviously is keeping all of your pier hieghth's level