Deck footings 48″ and as close to a lake as possible??
Anybody have any advise for me? We are purchasing a home with a lakefront parcel that we want to put a nice deck on. The code for footing depth is 48″. I have not designed it yet, but it will not be too large (maybe 16′ X 12′ or so) therefore i will only need 4 of them. There is some cheesy footings there now that i am sure were not dug deep enough and i will be removing. I am wondering just how i am supposed to get these holes filled with concrete if i hit water at 2′ or so when we dig?? I have poured some footings years ago for a deck at 36″ and we were able to drop a small pump in the hole just before we set the sonitube and started pouring in and had success however that was because we hit water at around 2′ and only needed to pour to 3′. This job was not on a lake but just had a high water table. I am not sure if this method will work or should i be looking into using some sort of pre-cast footings that we mayh have to jamb down into the water while backifilling the hole??
I am hoping someone who built bridges has some advise for me!! Thanks.
Replies
I've heard of doing it with a pumper truck (but, mind you, never seen it done). You bore the holes, let them fill with water, then stick the pump hose all the way to the bottom and pump in concrete, forcing out the water. You'd want the pumper guy to be familiar with the technique.
I have done quite a few PVC pilings for boat docks and you either use a pump or just a tremie to place the concrete at the bottom of the hole.
A tremie can be made with some 4" PVC pipe and something that will act like a funnel. One of the guys came up with a 4" to 12" reducer fitting and treated it like gold. Drill some holes in the form above grade (or water level for us) so the water has a place to get out.
I have also just seen them dump the concrete right in but from a bucket you want to do it fast so a big blob goes in all at once and it doesn't get diluted much. Use a very low slump mix.
Why not just go with pilings? Build it like a boat dock.
i will look into it
it sounds like a possibility. I never did any big construction of that type. I always did stuff with footings and concrete block or sonitubes in my ventures. Plus, i would think it will not be easy to find someone with a machined to do such a small job in this area.
I would also need for the building department to give me the go ahead for this method.
thanks,
I am not sure what machinery you are talking about. How hard is it to drill holes in the dirt? Can you do it with a post hole digger or do you need some kind of power auger? Blast??
A couple pf guys can set 8" pilings by hand if they are less than about 16 feet. How high is this deck off the ground?
Typically we set the pilings, chalk lines and then cut notches out for the stringers so you get a wood on wood connection, then through bolt them.
This gives you down load and upload capacity.
sorry
i have a wman power auger and have dug a ton of holes. I thought you were talking about pilings like i have seen shore homes built on and i never saw them installed. I thought they were driven down into the ground. If they are dug first then i would think the fill would be next to impossible to compact tight??
I can't let that one pass -- "wman power auger".
Must be one powerful wman!
i was tired and it was late!!
a 2man auger. thanks all. gave me alot to think of. I am just worried about ground heave I saw everything heave this year from the cold and i dont want to go through all this work and money to have a damaged deck after a rough winter
The problem with pouring the concrete in water is that most inspectors want to measure your depth first and i never dealt with this area so i am not sure what to expect. Some can be real sticklers for the code and they will not be able to measure mud.
Thanks again!!
You can always rent a trash pump. Pump the holes out for the inspector and get the concrete in there the same day (of rental)
In your case, you are probably site mixing the concrete for 4 piers. If they are 8" sonotube 4 feet long, that is only a couple of 80# bags per hole plus a little. I would just use the tube for going up from the last few inches in the ground and let the hole fill up completely so you will use more concrete. That gives you a better bite in the dirt. When I am doing a piling with a side load I use a #5 rebar cage in the middle but that may not be necessary for a straight down load.
i have used a pump as you suggest once
I have used a pump as you suggest once pouring footings but the holes filled up with water within ten minutes. I showed the inspector my process as he stood over the hole and he okayd my method. I am sure that i will be using 12" tubes because i know that i will have a bear of a time getting my arms and a tool down that low because th auger always leaves loose dirt below and from what i have read, the ground should be solid below the concrete. However, that wont be the case if it is mud now will it!!
I do like the idea of re-bar. i had done something similar years ago when i put a high wooden fence up and installed 10'posts in concrete. How would i set the re-bar?? Just drop it in around the tube when i am halfway up with the pour??
I just wont know the conditions until i dig. It is in the mountains but on water. this is the first project for us so we can enjoy the water immediately.
You may hit rock right away depending on where in the mountains you are. 12" is quite a footing for a deck. How big is this thing? Usually 6-8" is overkill. I understand concrete is cheap tho. I have six 12" footings under a shed.
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If you can get the bottom of each hole pumped out right before you start the concrete back in you should be fine. I am not even sure the mud hurts you that bad.
Usually when you do the rebar cage you set it before you start the concrete in there. Once you get much concrete in the hole, you are not going to push that cage down. You are trying to get at least 2" of cover tho so in a pour like this, maybe get a foot or so in, set the cage down 6-8" in the concrete and continue filling while you steady up the cage. Once it is covered in the concrete, it won't move.
i hear you
the only reason i would go 12" is that it is near impossible to dig 4' deep without going wider. So i usaually just go with the bigger tube and less dirt to fill(or foam it that happens). I am not sure how big we will make it yet because we need to come up with a design after we tear this old mess out and a few shrubs that are set off to one side. Probably not too big(12' X 16' or so). I am planning on running a dock off of it also, so that is why i am just not sure how far i am going to cantilever the joists off of the main beam yet, pending on how close i can get those footing to the water. Other guy thinks maybe i wont hit much water?? Hope he is right? I was wondering about that. Cant wait to start digging!! -(: I like the idea of the cage Thanks much.
Don't be shocked if the groundwater is pretty close to the lake level.
For something like this you can drill the holes and perhaps throw some gravel in the bottom, then lift and drop the piling a number of times to consolidate the aggregate at the bottom and backfill around it, tamping in the dirt.
We are talking about a "deck" ... right?
check
If you hit water. You may not. How hard could it be to dig one at the worst case scenario position and see what you get? Cross the bridge only if you get there.
Helical metal piers
Look into them. They're drilled into the ground, so there's no hole to fill with water. Gauging the hydraulic pressure on the machine lets the operator know when they've reached a layer with suitable bearing. I've watched a couple of installations, one in a situation similar to yours. TechnoMetalPost is one franchise that installs them. They might be pricey depending on your location, but they offer some advantages.
Concrete in Standing Water
Not exactly a recommendation, but there are 11 acres of apartments in metro Denver built on pier&beam foundations. Back in 1969, when I was a laborer, almost every bore filled with water. The GC had us dump concrete down the hole until it would accept no more. Slump? Don't ask. The engineer for the project "passed" a brick when he dropped by, but had no suggestions. Those apartments still stand. Ground was expansive clay, bentonite, requiring suitable remediation. Interesting project.
As long as you place the concrete at the bottom of the hole, there is no problem with water in the hole. It will simply be forced out the top. Since we are talking about a "deck" and I assume he is not landing F-18s on it like a carrierr deck, the compressive strength of the concrete will not be that big a deal anyway.
Bottom of the Hole?
Nice try Greg, but these holes had no bottom that the driller found, just water. He was careful to run his auger down the specified depth, giving it a bath. Probably surprised when the GC told him to continue making (watery) holes.
We dropped concrete, a LOT of concrete, straight out of the chute. Eventually it filled to the top of our improvised tubes. I mentioned that the engineer had a moment of distress when he saw what we were doing. But it worked out, 11 acres of 2 story apartments, with that bentonite to create more challenge. Now that I think about it, never saw the engineer make another site visit. His primary concern had been to ensure we left enough daylight under the beams to allow for expansion. IIRC, 5". Bentonite's interesting stuff.
I make it a policy to never argue against success. Those piers worked. Or enough of them did to hold the reinforced concrete wall, with apartments on top, up in the air. You're right, considerably heavier than the OP's deck.
No bottom? You punched ll the
No bottom? You punched all the way through to China? ;)
If you are saying you hit an aquifer/cave with a post auger, I wouldn't build a dog house there. That is a sink hole waiting to happen.
It is not unusual to have a drilled hole fill up with ground water here but the bottom of the auger is the bottom of the hole.
Deck support.
Someone has suggested drilling holes and setting wood pilings/post and back filing. You were concerned about compacting the back fill.
Instead of using soil for back fill, use foam. Our utilitie companies and the highway dept. uses foam to set their poles and sign post.
I used foam to set some wooden light standards for a little league ball field that had some water in the holes. As the foam expanded, the water was pushed out. That was about 20 years ago and they are still standing tall. Quick and easy. Google it.
appreciate it
that could be the ticket. i am using spray foam and foam board everywhere i can lately in my jobs and buildings now-a-days. It seems like it is a go to product for alot more than we would have ever thought of when it started hitting the shelf years ago.
thanks again.
look into a bigfoot with a base cap. they are really simple to put together and seals very well. built a large 2 story deck on the lake and they worked great.
our footers we only 36'' but we had 24'' of water in each one on at the bottom of our hill. pumped the water out, set the bigfoots in and no more worries.
i will
thanks.
Ground water and lake level not the same..
As suggested above, I would dig test hole near where you intend to place your footings. Yoiu don't say how far from the lake edge you are. There's not necessarlly any correlation to ground water and the lake level. The bottom of the lake is like a cup - it's saturated, but only to a certain depth - otherwise the water would just drain out. A good example of this is a resevoir - if the water were able to drain thru the soil, there would be no way to contain it behind a dam. There's a lot of folks with 100'+ wells on waterfront lots.
If there is water, the concrete will displace the water as you fill the hole, sono tube, big foot or what ever vessel you decide to use. Or use the precast idea that you had....I just saw an episode on This Old House where they used them very effectively.
A couple of years ago, we were putting an addition and deck on some lakefront land that was an ancient landslide (Seattle area). We could not good brearing soil (at least not godd enough for my structural engineer), so we ended up using pin piles - basically super long nails driven into the ground - may not work with your ground freezing expansion...