Well, I finally had to get it done…put piers under house. Not that I did any of the actual work, of course. All I had to do was take pictures and produce a checkbook. And be overly curious about home foundation repair process, (since it was happening to my home) and be generally in the way.
The ongoing drought took its toll on the soils.
I’d been trying to avoid calling the foundation repair companies for the past five to six years and writing about in on this humble blog. But the weather has just been too dry for the past three years where I live. And that is hard on slab foundations built on expansive clay soils.
These types of soil expand when they gain water and shrink when they lose water, all of this usually due to weather.
Why do they do that?
Heavy Clay Soils Are Bad for Foundations and Basements
Expansive clay soils are comprised of small, negatively charged plates. These particles attract water molecules which are slightly polarized, resulting in a potential for a big change in volume as water is adsorbed.
Then when the soil loses water and dries out through desiccation, the opposite action happens to the volume. It shrinks. If you are seeing the soil around your foundation pulling back from the slab or basement, that’s why.
Soil experts measure this shrink-swell potential in expansive clay with properties such as the “plastic limit”, “liquid limit” and the “plasticity index” which is the mathematical difference between the two (and has nothing to do with bosoms of strippers or so I’m told.) The higher the plasticity index, the more potential for expansion when wet and shrinkage when dry, leading to foundation movement. And my slab foundation sits on this kind of stuff.
The shrink-swell clay soils have what is called the “active zone”, meaning how deep down does this soil movement take place. It varies geographically. In Houston, Texas for example, the active zone is typically 6 to 12 feet. Things like drainage, trees and shrubs, the water table and climate affect the depth of the active zone.
In the U.S. expansive clay soils are found mainly in the Plains (which of course makes me think of that song from “My Fair Lady”) and the South Eastern states. Both areas of the country have seen off and on drought these past few years resulting in hard times for home foundations.
Trying to Forestall the Foundation Repair Companies
Over the years I’ve done all the things the homeowner can do to protect my foundation from movement. That means keeping the moisture content in the clay soil around and under the house foundation as even as possible…not too wet, not too dry.
I pulled out the large shrubs that were along the west and north sides of the house. I had Nellie R. Stevens hollies on the north side that grew as large as small trees if I didn’t get the pruners after them. (I was also allergic to them and was happy to see them go.)
Bringing in A Structural Engineer
At the recommendation of a structural engineer, I had four root barriers installed to keep tree roots from reaching the foundation. One of them was to keep a neighbor’s tree roots away from my slab. The reason for tearing out the shrubs and installing the root barriers is to make sure vegetation is not pulling water out from under or near the slab. A large tree can suck a lot of water out of the soil.
I also had the structural engineer do a formalfoundation inspection. His advice was to wait six months after the root barriers went in, but in his report, recommended piers all around the house eventually.
I ringed the foundation with soaker hoses and tried to run them faithfully when the weather was dry. Soaker hoses are made of recycled tires and are porous, enabling you to dribble water around the foundation in an effort to keep even moisture. You can get soaker hoses at the hardware store and the big box home improvement stores.
Still I was getting the classic signs of foundation movement. I had diagonal cracks in the sheet rock near windows. I had cracks where the interior walls and ceilings come together in a couple of bedrooms. I had areas where the drywall tape would either pop out or bunch up. I had bedroom doors that would swing one way or the other and not stay without a door stop. (Certain old heavy yet small stuffed animals were assigned that task.)
I thought the drainage around the foundation was OK. The idea is to make sure water drains away from the slab and not pond. Ponds are fine at the park, but not around your house.
Then I hired a North Texas foundation consultant named Richard Rash to look at my situation. Mr. Rash spent some thirty years in the foundation repair business and now gives advice to homeowners for a fee.
He thought I could do better with the drainage, that I might need piers under the north side of the house, but that my biggest problem was a water leak under the house. He said he could tell this by the pattern of damage to the sheet rock inside the house, that thirty years of experience taught him this, the way the old cop who just pulled over a young punk knows he’s being lied to.
Sadly for me and my check book he was right about the slab leak. A plumbing company with the equipment and expertise for such things found not one but two leaks in my outgoing water system. Yes, that would be the sewer lines. They did pressure tests that indicated a leak then found two of them using a tiny video camera they sent through the pipes. I could see the leaking water in the video monitor.
What this meant was, every time we showered, washed the dishes, did laundry and used those flushy things we were putting water under the foundation.
The plumbers had to cut through the floor and slab in my laundry room to get to one of the leaks, and tunnel from the outside to get to the other one. The culprit was 35 year old cast iron sewer lines that were failing, causing holes and cracks. The plumbers replaced every cast iron line they could get to with new PVC and the leaks were stopped. I write about that whole business here.
So I hoped that some of those wall cracks would close up since I was no longer causing upheaval under the slab with too much water from the slab leak. I waited six months for improvement. It didn’t happen. It was wishful thinking, like the Cubs ever winning the Series or peace in the Middle East.
Time To Call A Foundation Repair Company
I know I advocate getting at least three bids, but here’s the deal. When I see foundation repair happening on my street, I’m there with a camera and questions.
I’ve stuck my not very small nose into 4 jobs done on my street over the past 2-3 years. Two of them were the next door neighbors on either side of me. I know what method was used by what company, how many piers and for how much. Like I said, I’m nosey. so I was pretty sure the foundation repair cost using pushed piers was going to fall into the $5200-$7,000 range depending on the number of piers installed.
I called two foundation repair companies. One it turns out does only steel helical piers which I think would be over-kill for this entirely flat neighborhood.( Helical piers I think are most useful on property that slopes.) They would be pricey.
Then I called the contractor who did my root barriers and soaker hoses. He also does foundation repair and has done so for over 25 years in this area. Last time he was out he didn’t think I needed house leveling. But that was the first year of the dry spell and five years later he could see that things had gotten worse.
The Cost of Foundation Repair
He could tell by the damage the direction of my foundation movement and suggested pushed piers under the north, west, and south sides of the house, 15 in all. The foundation repair cost $4875 or $325 per pier, pretty average for this type of pier in North Central Texas.
Confession: the structural engineer I used does not recommend pushed piers on paper. In other words, written down. (yes he is an expert witness sometimes.)
He’s opinion is that pushed piers cannot be inspected as well as drilled concreted piers (bell bottom piers) or steel piers. But he told me verbally that pushed piers probably work fine 90% of the time. So yeah, C.Y.A.
An advantage of the pushed piers is that most of the time the job can get knocked out in a day. Maybe two if you have to have interior piers or where they have to cut concrete out of patios or driveways to install them and then replace the concrete with fresh cement and let it dry.
How The Job Went
Thus it happened that the crew got here on a Tuesday morning this past July and got after it. While the trucks were unloaded of tools and concrete cylinders, the foreman marked off where the piers were to go under the slab, using a diagram provided by the contractor.
Shovels were sharpened and crew dug holes under the foundation where the foreman (Omar) indicated. The dimensions? Big and deep enough to fit a guy, a concrete cylinder, and the hydraulic jack head that goes between the slab and the cylinder. Good sized hole.
If you have landscaping around the foundation the crew will dig out the plants, set them aside and re-plant when the piers are finished and the holes filled in.
A soon as the first holes were ready one of the crew started pushing the concrete cylinders into the ground under the edge (or beam) of the foundation using the hydraulic jack with the slab acting as a fulcrum. As one cylinder disappeared into the ground another was stacked on top of it and pushed down. It’s the stack of these cylinders that make up the pier.
This goes on until the cylinders physically won’t go any deeper, can’t be pushed any deeper. The engineers and foundation repair contractors call this “the point of refusal.” The workers call it “won’t go no more.”
The theory is that once a pier has reached the point of refusal it has reached either bedrock, or more likely a “stable” layer of soil that is beneath the weather affected zone.
It’s quite apparent when that point has bee reached. The hydraulic jack starts complaining with a whiny sound and when its pressure is released the foundation (been acting as a brace, remember) drops noticeably. You can see this right at the end of this video:
Can this cause more foundation damage? Critics say yes, and it probably happens now and then. But my slab went through it fine and most do. Creepy but fine.
After all the piers are in, a cap is placed on each. The caps are wide enough to accommodate two more cylinders side by side. But not yet. One cylinder goes on the cap and next to it a hand jack. These jacks have handles that you pump up and down like when you change a tire.
A flat piece of steel is placed between the slab and the jack head and the jack is raised enough to make contact with the slab. This goes on at each pier, and now the actual house leveling is ready to start.
Omar the foreman fetches his Zip Level, takes off his shoes, and goes in the house. He spreads the tubing from the Zip Level from the center of the house into each room like spokes. Using readings from this tool he can tell how many inches each side of the foundation needs to be raised to reach level-hood. And from experience he knows how many pumps of the jacks will raise the foundation how much.
He gets a worker with a jack at each pier hole along the north side of the house and halfway across the back. As Omar counts out loud so all can hear, the crewmen pump their jacks in unison with the goal of lifting that section of the slab all at the same time. The following video shows a session of the foundation raising.
Omar goes back in the house, checks the readings of the Zip Level, goes back out and counts out a few more pumps of the jacks. Back inside he takes his readings, is satisfied and directs the crew to shift around to the second half of the back and along the south side of the house. Rinse and repeat until he is happy with his numbers from the Zip Level.
Pushed Piers Meet The Slab
The next step in the my foundation repair is to make a connection between the top of the piers and the slab. This is done by hammering steel shims between the aforementioned points. Remember, we’ve got space for two concrete cylinders on a cap over each pier. The shims go in between the slab and the first cylinder. Then the hand jack is removed and replaced by the second concrete cylinder. Shims are hammered in between that second cylinder and the slab foundation.
The same work is done on all 15 piers and the underpinning is essentially complete. Omar checks his readings again at the Zip Level and declares my foundation level. Cool.
The final part of the process is filling the pier holes back in, replacing any plants and cleaning things up. My foundation repair is done.
Here’s a picture of the diagonal crack in the brick showing that it closed up quite a bit.
The next question is how long do I wait before fixing the cosmetic damage to the drywall and such? I’ve read and heard opinions all over the map on this one..from “don’t worry about it” to “wait at least three months” to make sure the foundation has stabilized.
Omar’s advice? Considering mine is a relatively small single story structure, give it a week. If it was 2 or three stories with a heavier slab, you would probably be advised to wait longer before taking on sheet rock repairs.
Repairing the Inside Damage
Within a couple weeks I had different crew come in, fix the cracks, do painting touch ups and install crown moulding throughout the house. If I still have issues where the walls and ceilings come together, the crown moulding will go a long way in hiding it.
So that’s the story of my house leveling. I hope I’ve been able to paint a picture of went on at my place during the “pushed piers” method of foundation repair.