What to backfill with - blackland

[swamp donkey]

Hello everyone, my name is Chuck. I've been a member on GF since 2010 and have been lurking on-and-off quite often. I have a good bit of construction experience in my background. I've built a total 4 houses and 5 shops (steel construction) in my days alongside my Dad and brother. My profession is Electrical Engineering so my attention to detail is absurd or ****-retentive as my girlfriend says!

So, I'm just about to break ground on a 32x50x12 "pole barn" build at the new house. My question is what material I should use as a backfill for the posts with the dreaded blackland soil? Aka "Devil's Dirt" haha. Right now the soil is well saturated due to record setting rains in 2015. But in the summer time there will be cracks 2-3" wide. So I'm very concerned with what to use as backfill - last thing I want is the soil pulling away from the posts 6 months after the build!

I'm excited to discuss and can't wait to build!

 

[jives]

Gravel. Not sure what terminology is used in Texas, but you will get suggestions on using fines mixed in with crushed stone (normally 2" minus), or plain ol' bank run, or dirt, or crusher run (stones, no fines). It will pack better with fines, but will not drain.

I would avoid bank run (too many big stones), don't worry about draining, and pack as tight as I could with a 2 minus gravel with fines (out here we would call that an Item 4).

You will get different ideas.

 

[theoldwizard1]

Gravel. Not sure what terminology is used in Texas, but you will get suggestions on using fines mixed in with crushed stone (normally 2" minus), or plain ol' bank run, or dirt, or crusher run (stones, no fines). It will pack better with fines, but will not drain.

Gravel is the answer, but 2' minus is awful large for back filling post holes. More like 3/4 minus. Actually, straight 3/4" gravel is acceptable for post holes. As noted, different parts of the country use different terminology for the same thing.

You do NOT want smooth/round gravel, sometimes call pea gravel or river gravel.

The mix of coarse gravel and fine gravel compacts extremely well and is great when as the final lift when filling a large flat area.

If you have a deep area to fill and you want it to drain well, start with crushed concrete. Make sure it has no rebar in it. This is not available in all areas.

 

[Stuart in MN]

You should define what blackland soil is.

 

[Grimpala]

Small world, I'm from Greenville.

Good luck with the blackland, my suggestion would be to back fill with gravel and then keep an eye on it this summer when the cracks from hell open up and start to swallow the gravel. Maybe backfill with sack-crete once the ground opens up.

Then again, we have a barn out at grandma's that was built in the 50's and backfilled with the same dirt that was taken out of the hole and it's still standing today.

 

[Grimpala]

You should define what blackland soil is.

Clay and muck that is like a thick tar when wet and clumps/crumbles when dry. Sticks to everything it touches and swells like a sumbitch when wet and contracts equally as horribly when dry.

If you're not careful you can lose a cow in a crack during the summer.

 

[tac]

Clay and muck that is like a thick tar when wet and clumps/crumbles when dry. Sticks to everything it touches and swells like a sumbitch when wet and contracts equally as horribly when dry.

If you're not careful you can lose a cow in a crack during the summer.

And walking across a damp plowed field you you will be 6" taller.

 

[ishiboo]

Might want to put a big gravel pad down and go with a post-tensioned mono slab over the top if things are that bad. You won't be able to DIY the slab though.

 

[swamp donkey]

Gravel is the answer.. Actually, straight 3/4" gravel is acceptable for post holes.

The mix of coarse gravel and fine gravel compacts extremely well and is great when as the final lift when filling a large flat area.

Thanks. This is what I'm leaning towards.

Small world, I'm from Greenville.

Indeed. I grew up in Cash, just south of Greenville. We've likely ran into each other lol

Then again, we have a barn out at grandma's that was built in the 50's and backfilled with the same dirt that was taken out of the hole and it's still standing today.

I'm also considering this.. who knows with this soil what will happen in a few months.

And walking across a damp plowed field you you will be 6" taller.

This is so very true.

Thanks for the info so far gents. Sounds like gravel is the way to go. I just spread 20 yards of what one of the local truckers called crushed concrete in the driveway to access the building site. Time will tell how it holds up. I'm fairly certain it's going to sink and I'll be adding more this summer.

 

[Richard Cranium]

agreed, 2" will be too big, 3/4 washed would be your best bet, They remove the silt in the wash, so it will still drain

 

[K'ledgeBldr]

The soil is better known as "Black Gumbo" in Texas.
Technically, it's Vertisol.

https://en.m.wikipedia.org/wiki/Vertisol

As for what is best for your specific area (Black Gumbo runs from Texarkana to San Antonio; and varies greatly depending on actual geographic location), contact your location extension service or A&M's extension service for soil conditions specific to your locale. This along with the recommendation from your local AHJ should get you down the right path.

Here at GJ you could get all kinds of info- it's just not specific enough for your conditions.

 

[Falcon67]

You should define what blackland soil is.

Just be glad you don't have to deal with it. We know what it is LOL. My relatives are from the Caddo Mills/Greenville/Quinlan area.

The blackland prairie includes the Dallas area - I'd start with the building codes/foundation recommendations for Dallas. Hillsboro might also work, if they have any. When I last visited my grandparents grave site there, the cracks in the black soil were wide enough to stick your leg in.

 

[jives]

Yes, on second thought, 3/4" minus is best. You will want to put down a concrete pad on the bottom. . . either a "cookie" or pour 4" of concrete mix in the bottom.

 

[pablo94sc]

You should define what blackland soil is.

It's called gumbo in Arkansas/mid-south. It's river silt that turns into the slickest, boot stealing pudding when saturated, but when it dries it looks into a dry lake bed - cracked and hard as a rock! It's very fertile soil.

 

[bczygan]

Boy, you sure have a variety of soil types in TX.

Blackland soils are a special deal, so get specific information from local sources on how to deal with it. Here is a description of the soil type.

Blackland Prairie Soils:

The Blackland Prairies consist of about 12.6 million acres of east-central Texas extending southwesterly from the Red River to Bexar County. There are smaller areas to the southeast. The landscape is undulating with few scattered wooded areas that are mostly in the bottomlands. Surface drainage is moderate to rapid.

Both upland and bottomland soils are deep, dark-gray to black alkaline clays. Some soils in the western part are shallow to moderately deep over chalk. Some soils on the eastern edge are neutral to slightly acid, grayish clays and loams over mottled clay subsoils (sometimes called graylands). Blackland soils are known as “cracking clays” because of the large, deep cracks that form in dry weather. This high shrink-swell property can cause serious damage to foundations, highways, and other structures and is a safety hazard in pits and trenches.

Bill

 

[bczygan]

Boy, you have a lot of soil types in TX!
This particular one will require local knowledge and standard practices. Inquire there.

Blackland Prairie Soils:

The Blackland Prairies consist of about 12.6 million acres of east-central Texas extending southwesterly from the Red River to Bexar County. There are smaller areas to the southeast. The landscape is undulating with few scattered wooded areas that are mostly in the bottomlands. Surface drainage is moderate to rapid.

Both upland and bottomland soils are deep, dark-gray to black alkaline clays. Some soils in the western part are shallow to moderately deep over chalk. Some soils on the eastern edge are neutral to slightly acid, grayish clays and loams over mottled clay subsoils (sometimes called graylands). Blackland soils are known as “cracking clays” because of the large, deep cracks that form in dry weather. This high shrink-swell property can cause serious damage to foundations, highways, and other structures and is a safety hazard in pits and trenches.

Bill

 

[pmiranda]

Yep. Learn more about your soil here:
http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx

My neighborhood is on 2 feet of clay resting on limestone bedrock. My shop site in the next county over is a mix of soil types.

 

[Nowater]

As a hydraulic engineer talking to an EE, find yourself a Civil PE or a geotech PE and ask them. If you find a local person, they have probably already found a solution that works. I think it would be worth a consult!

 

[billspit]

First time I ever this stuff was in AL. There is a crescent strip that runs across the state. Craziest stuff I've ever seen. I support asking a civil engineer.

 

[theoldwizard1]

Gravel. When the soil cracks and the gravel sinks, just add more !

How deep are you planning on making the post holes ? Deeper than the cracks go I hope. Some places require a concrete "cookie" (about 6" thick with some rebar) in the bottom. Let set at least overnight before placing the posts.

 

[Streetbu]

I just spread 20 yards of what one of the local truckers called crushed concrete in the driveway to access the building site. Time will tell how it holds up. I'm fairly certain it's going to sink and I'll be adding more this summer.

You didn't put any landscaping fabric down first? Thats common practice here in the north east, figured every one did it that way.

 

[swamp donkey]

As a hydraulic engineer talking to an EE, find yourself a Civil PE or a geotech PE and ask them. If you find a local person, they have probably already found a solution that works. I think it would be worth a consult!

As of now that's my plan before digging. Thanks!

Gravel. When the soil cracks and the gravel sinks, just add more !

How deep are you planning on making the post holes ? Deeper than the cracks go I hope. Some places require a concrete "cookie" (about 6" thick with some rebar) in the bottom.

Seems like a simple solution to refill when necessary haha! But I'm hoping for something more permanent. I plan on punching holes 18" holes - 4' deep as of now.

You didn't put any landscaping fabric down first? Thats common practice here in the north east, figured every one did it that way.

Hmm.. never thought of that. Since the soil is saturated right now (no cracks) I thought I'd just experiment with this load as see how it handles traffic. Our driveway to the house (built in 2005) is crushed concrete and it's holding up surprisingly well.

 

[theoldwizard1]

Seems like a simple solution to refill when necessary haha! But I'm hoping for something more permanent. I plan on punching holes 18" holes - 4' deep as of now.

I don't think you can find a "more permanent" solution to soil that changes characteristics so much. You want a foundation that can "give" a little.

I do suspect that you won't be adding much gravel, if any, after 3-5 years.

 

[Trick414]

As of now that's my plan before digging. Thanks!



Seems like a simple solution to refill when necessary haha! But I'm hoping for something more permanent. I plan on punching holes 18" holes - 4' deep as of now.



Hmm.. never thought of that. Since the soil is saturated right now (no cracks) I thought I'd just experiment with this load as see how it handles traffic. Our driveway to the house (built in 2005) is crushed concrete and it's holding up surprisingly well.

I've fought the clay fight for about thirty years in Fort Worth.

Were building a new house in Corsicana. It's not as bad there, as it has more sand, but still plenty of clay.

Anyway, the very short story is that we ended up replacing most of the nasty soil with good fill.

We got a soil report. We looked at several different slab types. Ultimately it involved a combination of piers and soil replacement. I'm on a lake so that didn't help either.

But the end result is that I won't ever deal with that Damn clay ever again. It was a bargain at twice the price. And the price wasn't crazy anyway.

Sent from my 831C using Tapatalk

 

[Streetbu]

Hmm.. never thought of that. Since the soil is saturated right now (no cracks) I thought I'd just experiment with this load as see how it handles traffic. Our driveway to the house (built in 2005) is crushed concrete and it's holding up surprisingly well.

They make commercial grade stuff, in 12 and 16' wide rolls, perfect for driveways dig down a few inches, roll it out, dump your stone. It meant for water to go thru it, but nothing else. stops the stone from sinking into the ground and having to redo it every few years.

http://www.usfabricsinc.com/products/drivewayfabric

 

[jeff64]

Blackland is also called "buckshot" in east Arkansas, as in Buckshot Mudder tires. It packs like concrete when dry. Some people pour sand in the cracks around posts, but it is a never ending job.

 

[shanker]

I live in San Patricio county TX where we're covered with what we call black land too. It wreaks havoc on homes where people don't maintain a constant moisture level around their foundations and with sub-surface water pipes especially during periods of dought/floods.

Wouldn't lime help stabilize the soil? around here we haul in Sand and build up 2-4' thick sand beds where foundations are to minimize movement.

 

[My Old Tools]

Have you considered having pier holes drilled and concreted, then set the poles? I really don't have a good answer after 40 years in and around Greenville. Maybe move over to Union Valley like I did and get out of the gumbo. My 1910 house in Greenville was set on bois de arc blocks. They held up pretty good for 80 odd years. The trick was to keep water out from under it.

All the new construction in Rockwall requires the soil be injected with a stabilizer before any foundation work is started. You might look into it.

 

[swamp donkey]

.. But the end result is that I won't ever deal with that Damn clay ever again. It was a bargain at twice the price. And the price wasn't crazy anyway.

Sent from my 831C using Tapatalk

I agree. After a few years here I hope to never have to deal with it again. Good luck with your build!

They make commercial grade stuff, in 12 and 16' wide rolls, perfect for driveways dig down a few inches, roll it out, dump your stone. It meant for water to go thru it, but nothing else. stops the stone from sinking into the ground and having to redo it every few years.

http://www.usfabricsinc.com/products/drivewayfabric

I will definitely look into that stuff when we ultimately decide where to put the building.

It wreaks havoc on homes where people don't maintain a constant moisture level around their foundations and with sub-surface water pipes especially during periods of dought/floods.

Our neighbors can attest to keeping the moisture level constant - no problems in 10+ years with theirs. The ones that don't maintain are obvious when you're up close to the foundation. I've seen 3" from soil to slab on some houses around here.

Have you considered having pier holes drilled and concreted, then set the poles?

I think I'm leaning more towards a properly designed slab for the soil around here, then a custom welded steel frame. I'm too leery of the soil conditions to trust a pole sticking out of the ground 14'-20' to support my shop.

 

[pmiranda]

I haven't met anybody that did a pole building in clay, but the big question is probably what's under that... If it's a couple feet of clay on top of something that's more stable, then a pole building would be perfect, you just need steel in your slab to keep it in one piece as it floats up and down.
The standard foundation I've seen in most of Texas clay for homes is a "waffle" configuration, with deep perimeter beams and not-so-deep interior beams every 10 feet or so, with a slab on top and rebar throughout. I expect to need something like that for our steel frame shop build but I haven't consulted a local expert yet.

 

[My Old Tools]

19-22' to a solid footing in Hunt County. 600' in Houston.

 

[pmiranda]

Haha... 600' to solid footing in Houston... you mean the ocean floor?

 

[My Old Tools]

I think I'm leaning more towards a properly designed slab for the soil around here, then a custom welded steel frame. I'm too leery of the soil conditions to trust a pole sticking out of the ground 14'-20' to support my shop.

That's what I did. After 10 years I had Granite Foundation people come drive steel piers to lift it back level. Drilled piers are pretty much required to make a slab stay put.

 

[swamp donkey]

The standard foundation I've seen in most of Texas clay for homes is a "waffle" configuration, with deep perimeter beams and not-so-deep interior beams every 10 feet or so, with a slab on top and rebar throughout. I expect to need something like that for our steel frame shop build but I haven't consulted a local expert yet.

I obtained a few quotes earlier this week and this "waffle" config is what all the contractors are suggesting. Hopefully early next week I can get started!

I plan on creating a build thread. Thanks for all the info guys!

 

[theoldwizard1]

I obtained a few quotes earlier this week and this "waffle" config is what all the contractors are suggesting.

INTERESTING ! Never heard/seen this before, but we don't have similar soil conditions here in MI.

Would this mean a traditional "pole building" is out ? Check around for "all steel" buildings. There have been a couple of recent threads on these. (I would stick with 4' "stud" and rafter spacing. Easier to use other building material for insulation and interior walls.)

 

[My Old Tools]

Steel (red iron) shop buildings are pretty much the standard in this part of the world. Outside the city limits it is rare to see a house without one out back.

 

[AP2TUDE]

Such a small world, I am here in Rockwall.

We are building our home very shortly off of the 548 and the foundation is the single most expensive portion of the project. We are going with a combination of a pier and beam setup along with chemical injection to try and stabilize the soil.

Moving from Southern California where all the ground was hard as a rock and comprised primarily of decomposed granite, the soil here couldn't be any more different.

 

[Grimpala]

Such a small world, I am here in Rockwall.

We are building our home very shortly off of the 548 and the foundation is the single most expensive portion of the project. We are going with a combination of a pier and beam setup along with chemical injection to try and stabilize the soil.

Moving from Southern California where all the ground was hard as a rock and comprised primarily of decomposed granite, the soil here couldn't be any more different.

What side of I-30 are building on?

 

[swamp donkey]

I forgot to add a link to my build for those that are interested...

http://www.garagejournal.com/forum/showthread.php?t=324620

 

[Falcon67]

Haha... 600' to solid footing in Houston... you mean the ocean floor?

LOL, the first 599 feet is sand. I can rain like a SOB, can't see 10' for 3 hours and when it stops not a puddle anywhere.