Concrete piers in wet soil...Need advice

Hey all...

I got some good concrete advice in this post:

http://grassrootsmotorsports.com/forum/off-topic-discussion/diy-concrete-mixing-and-freezing-temperatures/17078/page1/

So I thought I'd ask again about concrete...except with a different problem.

Now I'm ready to pour some concrete piers for my front and back porch supports.

My basic plan is to dig a 32"+ hole with a posthole digger, mix up some quickcrete, pour it in, throw some rebar in, and then set a post anchor. Simple enough...

However, The ground is super saturated here and will be until spring is over. If I dig a post hole, it will be full of water within hours (minutes, probably).

It is my understanding that overly-wet concrete mix results in poor strength concrete.

So...if I dig a hole and fill it up with concrete, it's going to stay wet for a while. Is this bad?

I'm ready to roll on this, so I can make progress on the house, but I need to know the concrete will be up to the task (which is basically supporting additions onto the house).

It sounds crazy to me...but would lining the hole with a plastic bag before filling with concrete get me the desired effect?

Thanks!
Clem

Whatever you do, don't set them during a full moon. They'll surely come up if you do. Seriously. Ask any farmer about setting fence posts during a full moon.

Lol...noted.

For the record, I won't be setting the posts in the concrete, but rather ON it. (not that it really makes a difference to the moon).

Google dek block. This may keep you away from a lot of digging?

Hello? Mom?

You could use a deck block and avoid the digging thing altogether if it'll work for codes and whatnot in your area. Or, buy a length of sonotube, cap off the bottom end with some heavy plastic and duct tape (enough to keep the water mostly out for a little bit- once the concrete sets it won't matter if it's wet) and set your footings that way. Maybe?

Alternatively, wait until the yard's not soup to set your footings?

She probably cant hear you over the concrete mixer?

TRoglodyte wrote: Google dek block. This may keep you away from a lot of digging?

Not an option.

It's not just a deck...it's a roof extension and will be in integral part of the structure of the house. I want and will have piers.

Thanks folks!

Clem

I poured piers for a lake edge deck at our cottage using the following technique. Insert a sonotube into a construction duty garbage bag then drop the bagged sonotube into your hole. You'll have to have an helper hold the sonotube down while you fill it with concrete or else it'll try to float, guess how I figured this part out. You can buy heavy duty garbage bags at Home Depot, Lowes etc.

They make waterproof concrete bags for just this situation. They use them to set piers on sand out here in Earthquake country so it should be more then enough for your project.

Datsun1500 wrote: GRM way: Dig hole, look at water filled hole, pour in concrete mix, stir. Not how I would do it though....

Done that for mailbox posts. As far as I know it's still standing after 20 years.

Wayslow wrote: I poured piers for a lake edge deck at our cottage using the following technique. Insert a sonotube into a construction duty garbage bag then drop the bagged sonotube into your hole. You'll have to have an helper hold the sonotube down while you fill it with concrete or else it'll try to float, guess how I figured this part out. You can buy heavy duty garbage bags at Home Depot, Lowes etc.

I vote for this technique. As noted, be ready to anchor the sonotube so it won't float upwards. Or you can dig the holes and widen the bottom (the hole winds up shaped like a lab beaker). Pump out the groundwater, stick a big plastic bag in the hole and then QUICKLY pump it full of concrete. You might want to drop a hose in the side of the hole (outside of the bag) so you can pump water out if it starts to become a problem.

Concrete will harden underwater but as noted unless you know just what you are doing groundwater getting into the mix could very well lead to cracking etc later. It might be plenty strong enough for a mailbox but maybe not so much for a roof post.

if its structural (for the house, not just a deck), go as deep as you can.

my town says i needed 44 inches.. i went 54 (deep as the digger would go)

deeper is better. always....

Sonotube!! Rent a power post hole digger, yaws through anything.