yet another foundation question

[tesa]

ok, daniel and i are ready to break ground

our soil is loamy fine sand with a 1-5% slope.  at about 4feet down, we hit water, even last summer, during 5 weeks of no rain,
while setting our fencepost, we hit water at 3-4 feet

not sure how much that matters, but i thought i'd mention it

p.t. post foundation plans call for the post to be placed on dbl 2x12" p.t. plate, which is placed on a footing of concrete OR
crushed rock pad

so my ? is, can we just dig the hole 24" wide, 36" deep and place 12" of gravel, then the plate that the post will be bolted to
OR do we have to use poured concrete for the footing

we have no inspecters, no permits, and no one for me to call to get advise for my area (grimes county texas)

we'd like to not have to pour concrete, but with the fine sand we live on, would it be better?


i'd like to just use cgravel for the footings but would rather hear from someone here before i rule out concrete

tesa

[John Raabe]

Any chance you can find a more suitable, stable site?

Sounds like you're planning to build in a bog or wetland. I'm just guessing from your description and maybe it's not as bad as I imagine.

The post and pier foundations that I show in the plans are for solid well-drained soils. I don't know how they might perform in saturated fine sand and loam.

I went to the Grimes County website and found that they have a Cooperative Extension program. They might have information and maps of soil types and how suitable they are for foundations. What do other houses in the same soil have for a foundation? Look especially at houses that are over 50 years old.

In good dry soil you can use crushed rock and it will spread out the point load of the post onto the soil below. A concrete footer with a cast in post bracket will give you more stability against uplift and side movement. The footing should be half as thick (deep) as it is wide. In soft soils a wider footing is more stable, but I can't tell you what would be the right width for your specific soil.

If you are building the 1-1/2 story plan you might want to consider the concrete crawlspace rather than the pier and beam foundation. That has a continuous reinforced footing that can even out soil issues and bridge soft spots.

[tesa]

i spoke with the extension agent, as i'm taking the master gardeners class thru them, and he wasn't much help
he said to consult the soil survey, which i did, and was able to find out about our loamy sand

other homes in the area are built on top of the soil, we were able to watch someone down the highway build, as
we pass by the area on the way to town, he just layed concrete blocks on TOP of the soil, and started to go up
from there

our neighbors have a home build on blocks on top of the soil

but they have a single story, no loft

we have the second highest property on the street, as we're near the top of a wee "hill", which we thought was good

and, the house site is the highest point on our porperty

tesa

[John Raabe]

It sounds like the soil may not be as bad as I imagined, or, at least others have faith in it. 

You probably have little likelihood of deep frost or soil heave where the ground can lift a shallow foundation. No chance of earthquake or tornado strength winds?

If all of that is NO, then your plan for the PT wood posts and gravel footer should be fine. As long as the ground is stable and will hold the gravel without "mushing out" under load the water itself is not a problem. Dig as wide a footer as you can and be sure to brace the PT posts back to the beams (as shown in the plans). Protect the posts with tar or waterproof membrane near the surface as that is where the post will be most subject to insect damage. Doing so will extend the life of the post.

If you want to go to the extra trouble of the concrete footer and post bracket you will have an extra margin of safety and stability.

[tesa]

thank you so much for your never-ending help and support

daniel and i spoke quite a bit last night, and decided, we are going to go with the solid concrete footer

we want this house to last for our children, thats why we're doing it in the first place, and don't want to
skimp on such an important component as our foundation

we have a few stumps left to remove, and then its time for the layin' of lines! 

i've waited along time to see that square of twine!

will continue with updates as i can

have a wonderful day!

tesa