# adding piers under house



## phnola (Aug 15, 2010)

hey all, 

i have a couple of concrete block piers to install under a single story shotgun house down in new orleans that was a victim of contractor fraud. basically they stopped the middle 6x6 sill halfway back, so that only the first half of the floor joists are supported in the middle over the 18' span. So i basically need to build four block stacks so that the middle sill can continue all the way to the back. 

i would greatly appreciate some expert advice/ feedback from some masons on building these piers. my current plan is to pour 30x30x8 footings over tamped down gravel and a plastic vapor barrier. these will have four 24" long pieces of #5 rebar, and will also have four pieces of rebar extending vertically (2 for each cavity of the block stack). the block stacks will be four blocks high with approx 1/2 " mortar joints and then we'll fill the cavities with concrete, and add a termite shield on the top before setting the sill. 

i appreciate any feedback. how do you all do your piers?


----------



## dakzaag (Jan 6, 2009)

I wouldn't figure on half inch mortar joints, but if your short, you can always shim it. 

Hope your not laying those with the deck on, that would suck.


----------



## Framer53 (Feb 23, 2008)

Why the vapor barrier?


----------



## lukachuki (Feb 11, 2005)

that would be more than adequate for around here. A comfortable block joint is 3/8 of an inch. Laying em under an existing house is "high" dollar work. Or at least it used to be.

I don't think the vertical rebar is necessary and would make the job much more difficult if building in cramped workspace. We are just talking compressive strength here and brick mortar and concrete have plenty of that. I'd def. put it in the footer though.


----------



## 2low4nh (Dec 12, 2010)

We usually jack the joist up if we can to get the extra 1/4" of space. what is the existing floor under the house? is it a concrete slab or dirt? I would assume there is no frost down there so the depth isnt a major concern. I would look at the soil under the floor. Is it heavy clay? remember you do this the pier sinks its your butt not the first contractor.


----------



## phnola (Aug 15, 2010)

hey all, i appreciate the replies. yes, unfortunately, the deck is on, so we have about four feet of crawl space to work with, which sucks but definitely could be worse. my plan for getting the sill in there is as follows: 

i ran a string line from the bottom of the middle sill to the bottom of the sill at the back of the house where the middle sill will tie in, to give me a height for the footers. i then made the height of the footers so that four blocks with 3/8 inch mortar joints will meet the string line. once we've set our block stacks, i think we'll set up some 16' 6x6s on either side of the middle and jack up the house an inch or so, enough to get the sill in there, and then lower the house onto the sill, which should be at the correct height. any one see glaring problems with this strategy? thanks


----------



## Paul's (Oct 14, 2010)

I did a housing project once where the framing plan and the foundation plan were not in sync. When framed the main beam was only 2 in from the edge of the piers. The nitwit inspector wouldn't pass the completed house due to this problem. But he would pass it if we ran 2 in biscuits stack bond up the short side. Moral is.. keep in the center and remember not to stress out. They make all kinds of sizes of blocks to fix your problem (correctly, I hope) Width of footing is more important than depth. Sorry for the ramble.


----------

