Anyone have input to a little problem I ran into today? Here’s the situation: I am building a deck in Southern Michigan. It is located on a small lake. The deck will be 20′ by 24′. It will be located parallel with the lake about 4′ from the waters edge. There is a seawall in the 4′ space, with the top of the seawall being several feet above the water.
Michigan code requires footings to be 42″ deep. As I dug my first hole for my sonatube liner, I hit water about 30″ down. At first a trickle but the hole did fill up. This is at the top of the deck about 24′ from the water and about 18-24″ higher than the top of the seawall. I am positive there is no way I can dig a 42″ deep hole without it caving in and filling with water. And when I get closer to the water, since the ground is sloping towards the lake, I think the water table will be higher yet. I may not be able to dig 24″ down before hitting water.
What are my options? Dig until I hit water and fill it with concrete? Anyone used those little precast piers sold at the home centers? I believe they set directly on the ground.
No permit is required so there will be no inspections, but I do want to do the right thing. According to State and County Building codes, per Mr. Inspector, no permit is required unless the deck in question will be more than 30″ off of the ground, which it is not. I had his permission to proceed with no permit/inspections needed.
I’m looking forward to your comments. I’m sure I’m not the first one to run into this!
Replies
Sounds like you need to set it on pontoons. ;)
Actually, on one deck I built, I had a similar problem after a hard rain, with groundwater filling some holes that I had dug for deck piers. I would use my shop vac to suck the water out, and ten minutes later the holes would be full again.
I finally ended up shop vacing the holes one-by-one, and lining each hole with a trash bag and immediately filling them with concrete. The trash bags kept the water separate from the concrete so that the mix did not get weakened.
Good luck.
Sounds like one of those, "you really have to see it firsthand, to give a professional evaluation." So without seeing it firsthand, here goes.
Dig your holes as deep as you can, even with water penetration. Dig these holes 24" square. Tie a grid of rebar for each "footing". Tie two vertical pieces of rebar, (with a minimum 6" 90 degree bend), into the grid that project up the center of where your sonotube will be. Pour these footings 8" deep. Mag off the top of the concrete then set your sonotubes into the footings, insuring proper placement and plumbness. Next day you can cut sonotubes to elevation, brace and pour. The rebar is continuous so it can be done in two pours. If you're feeling really ambitious you could try monopouring the two. At the tops of the sonotubes I would use the adjustable post/beam brackets. With that much groundwater there is bound to be some settling, and these brackets make it simple to adjust for that.
Most recreational lakes around here are lowered quite a bit sometime after Labor day until around Memorial day.
This facilitates these type of projects. Any chance that the level will drop soon?
Caisons (sp), thats what you need, and a pump.........gonna break the bank though!
Eric
we had to dig footings on a lakeside cottage.. the ground level was about 2' above the lake level..
i went to our Town highway dept and bought a bunch of aluminum drainage pipe cut-offs... they were about 24" diameter.. then i dropped each on in the hole and used them as caissons (?) excavating from the inside and sinking them as we went down..
this was an inspection job.. so when we were deep enough i mixed a bucket of hydraulic cement and dropped it in.. it sealed the botom well enough that i could dry the hole enough for the inspectorMike Smith Rhode Island : Design / Build / Repair / Restore
Dave,
Even after you told the Inspector you hit water at 30" he still told you to proceed?
I would talk to an Architect or Engineer.
Joe Carola
I'm curious that you can build so close to the lake. I know in Minnesota the Department of Natural Resources has definite rules about how close structures can be to water, and they have to be a lot further away than that. You may want to check with the Michigan DNR to see what they have to say about it...
Does anybody there build piers out into the lake? If so, perhaps they'd have some relevant ideas.
-- J.S.
Put a call in for Dino....
Who ever invented work didn't know how to fish....
Quit digging.
Get some long treated pilings and water jet them in.
Frankly, I am amazed at the diversity of opinion and understanding on this problem. I saw the title and said to myself, "So, what else is new..." My pump has been busy lately.
I hit water as often as not for sonotube/pier footings. This is just a deck so some of the advice is overkill.
My thinking about building so close to the edge is that the house is already there, so it is grandfathered. most regs allow for a cetain percentage in increase in footprint too.
There is a product made of plastic called bigfoot you can set with the sonotube or buy as a complete bell. Dig, set it in the bottom and pour low slumpo to float the water out of the hole.
Alternate solution - dig to the right depth, throw in an unopenned bag of Sakrete flat in the bottom and set a 6x6 PT post on it. Wrap the post in saran wrap first for the below grade portion. Then backfill, with the post braced plumb of course.
The ground water will make the bag of 'crete set up without mixing and the saran wrap or other plastic will prevent the frost from grabbing the post and heaving it up and out.
In answer to your basic question, Yes, you definitely need to be down below frost level. If you stop digging at the water, then when the water freezes, it will lift the post out of the hole. I would dig as deep as I could tolerate.
Excellence is its own reward!