Concrete Block Piers

Started by trp, January 26, 2009, 01:17:33 PM

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trp

Just joined this forum hoping to be able to learn from others and to share my experiences.

That said, we are building a small country home in the Southeast Texas area.  The soil is composed of a fine sand over white or red clay.  The area that we are building is fairly deep sand 5-6 feet and on a slight slope of about 1 inch per foot.   The foundation consists of drilled piers of 12" diameter by 3 feet deep with a 20"x20"x6" pad on top.  I am using four 3/8" rebar tied to four cross rebars in the pad.  Centered on the pads will be 2 - 8x8x16 concrete blocks that are mortered and filled with concrete and rebar.  We will use one set of blocks in the front and probably as many as five stacks of blocks at the back of the house. 

The pier spacing is about 7 foot maximum centers for the floor joists (that sit on the treated beams) and about 8 foot centers for treated beams (that sit on the piers) running perpendicular to the floor joists.  We plan on using cracked blocks and no skirting, so there will be good access under the structure.

Two questions:
- what is recommended to tie the treated beams to the piers
- Any recommendations for the soil under the house so that it is very stable and easy to crawl on to do any maintenance on plumbing, etc.  Currently we have brought in a "sandstone" material the forms a nice surface when kept dry.  We are using a french drain of gravel to divert rain water around the foundation area.  Has anyone found other materials that work well for this?

Thanks for any help.

Beavers

I'm at the same stage of the game as you are.. trying to decide on the foundation design.  So, If you want the opinion of a complete rookie, here is my 2 cents... ;D

I would think that you would want the 20x20 pad at the bottom of your piers, everything I have read shows the footings at the bottom.

Why not go with either all Sonotube or all concrete filled block for the piers?

I was having trouble finding Sonotube in lengths longer that 4 foot, but I found on the Sonotube website that they can be spliced together for longer lengths.  The Sonotubes should be easier to fine tune the height on, with the block you are stuck with 8" increments.  On the other hand the block seems like it would be easier to fit skirtiing to.


If you Google Simpson Connectors, you will find pictures as well as descriptions of every kind of connector you could ever imagine, including beam to pier connectors.


BTW- Why are you going three foot down with the piers?  You can't have much of a frost depth in Texas... is it because of the sand or what? ???


ScottA

I embeded a long 1/2" anchor bolt in the filled blocks then drilled a hole in the beam to drop over the bolts. You can also buy special connector plates that you can bolt down then fasten the beams to those like Beavers suggested. I'd put down pea gravel under the house if you need something there.

MountainDon

The pad on top does not make sense to me either.  ??? The pad is for spreading out the load over a larger area lessening the load per sq. inch.  A pad at the top in a location that freezes would be a definite no-no as that would encourage frost movements.

Simpson make a variety of connectors that could be used. Some of their post bases could be used to hold a beam. They also make special brackets for concrete to glulams.

Just because something has been done and has not failed, doesn't mean it is good design.

trp

Quote from: ScottA on January 26, 2009, 05:57:32 PM
I embeded a long 1/2" anchor bolt in the filled blocks then drilled a hole in the beam to drop over the bolts. You can also buy special connector plates that you can bolt down then fasten the beams to those like Beavers suggested. I'd put down pea gravel under the house if you need something there.

Thanks, Your suggestion is simple and where I can align the block holes correctly, I will do it.   Would you suggest such hold downs on all piers, or only at the end of the spans?  I plan on using a stone veneer around the blocks, so getting the outside of the veneer to align with the siding and get the main beams under the load bearing walls is a little trickey!  Probably a smaller gravel will work well as a nice surface, especially if I tamp it into the sandstone.  I will also use "turf locs" (concrete interlocks) to hold the sandy soil in place around the perimeter of the house (drip line).  Erosion, runoff control in heavy rains is a real issue on this sloped home base.  Any suggestions are appreciated.

Mark


ScottA

I used bolts in all my piers. I'm also going to put stone veneer around the piers.

Mike 870

Quote from: ScottA on January 30, 2009, 08:40:42 AM
I used bolts in all my piers. I'm also going to put stone veneer around the piers.

Hey that is a good idea, kind of like what you see on porches of some of the nice custom craftsman homes?  I think that would look really nice.

hnash53

I don't think in Southeast Texas there's going to be any movement in the foundation due to cold weather.  Perhaps movement due to other things but certainly not frost heaving.

Hal, ex-East Texan.