Foundation Pier Types, Lifting, and Voids
Not all foundation pier types are the same.
The best pier types are the ones that hold the best. And those aren’t usually going to be the cheapest option. But as with most things in life, you get what you pay for.
Weather Affected Zone
Let’s quickly cover what the weather affected zone is in a foundation.
As I mentioned in a previous post, our expansive clay soil in the Dallas/Fort Worth metroplex contracts when it’s dry and expands when it’s wet.
So the piers, any of them, need to go below the weather affected zone. Some people also call this the active zone which is about seven to 15 feet below ground in the Dallas area. Otherwise, the soil movement will make the piers shift like crazy.
Any pier, regardless of pier type, that does not go below the weather affected zone will not support or stop the house from moving.
With a press piling, concrete cylinders — like the ones in the picture — are stacked one on top of each other.
Some companies insert a cable down the middle of them, something like rebar, etc.
Now they make these looks really good on paper. But just because it looks good on paper, doesn't mean it is. There are many situations where the pier ends up going in sideways underneath the house.
And with these types of pilings, they use the weight of your house to lower the piers. Where the problem comes in is if they can't lower the pier far enough because the weight of your house isn’t heavy enough. This makes it highly possible the piers won’t go below the weather affected zone.
Press pilings are, in my opinion, worthless in almost all cases. It is the cheapest option and it’s what most contractors use. If you're looking at JUST pier price, if the only thing that matters is price point, press pilings are what you're probably going to get.
But I can tell you, I would never personally install or recommend installing press pilings to anyone.
I know a press piling company in town and that’s 50% of what they do. And the other 50% is going back to fix things. In fact, they keep a warranty crew on staff at all times. The warranty crew only does warranty work.
With a steel pier, the contractor drives it into the ground.
It’s usually a thinner pipe so they can go down lower with these. But again, they are using the weight of your house to lower the piers.
So there's still no guarantee they'll go down below the weather affected zone. Although it's much more likely they will because of the smallness of the actual pier.
Now it's possible as well that these could also go in sideways, but that doesn't happen very often.
Helical piers, the most expensive option, are steel piers with one or more helical plates that anchors the pier into the ground.
It’s essentially rotated into the ground like a screw. It was designed to secure the pier in the ground. Foundation companies started using it for foundation repair at some point in the recent past.
The thought is that it will support the slab better. And they aren’t using the weight of the house to drive it into the ground so theoretically it should go down below the weather affected zone.
Drilled Concrete Piers
With a drilled concrete pier, they drill a hole into the ground and then pour concrete in.
With this type of pier, it's a longer process. It’s usually takes a week to two weeks.
The company brings out a machine that drills down into the ground. Then they put rebar down into the hole and fill it with concrete. And then the concrete has to sit for seven days. So your yard is torn up for 7 days or more.
This is an older way of doing foundation work.
But I'm a big fan of drilled concrete piers. You know exactly where the actual pier went. You can literally look down and see how deep it went, etc. Although this is what I’d recommend, there are some downsides to it as well re: the longer process, the messiness, etc.
But it is also cheaper (and better, in my opinion) than the steel or helical piers.
I cannot stress enough, if you’re going to hire a company to do mud or foam jacking, be sure to thoroughly research the company.
Mud or foam jacking is used to fill a void or to lift your house. But there are some potential problems with these methods.
In the case of lifting the house, they are pumping the mud or foam on top of the existing soil under the slab. So that soil is moving which means the mud or foam on top of it is also going to move.
However, this method is useful particularly in the interior of the house. They don't have to drill pier holes ( which are usually a foot and a half by a foot and a half, give or take) which often destroys the interior flooring.
So what they do instead, because a mud hole which is about a 2 inch diameter hole and a foam hole about 1/2 an inch, they can put that into a grout line and cover it so you won't know it's there.
Just keep in mind, mud or foam does not go down below the weather affected zone. Whatever is currently happening to your home because of the soil is still going to happen to your home because of the mud or foam.
And in cases of filling voids, the one thing you want to be careful about is you want to make sure that they don't overfill the void. It's extremely difficult, basically impossible, to extract that stuff back out once it's pumped in.
If you have a low slab now and you end up with a high slab, you have an even worse problem than before.
You also don't want to do this when there’s been either extensive drought or major rain. Both extremes are potentially dangerous times to do this.
You just have to be very very careful. There are some potential uses for this but you have to make sure, double check, even triple check the company doing it.
A good quality company has a long rep in the biz. They’ve been doing it for a long time so they have a lot of experience. Make sure you find someone with a lot of experience with what does work and what doesn't work. You don't want someone new who just started doing it.
A good quality contractor is going to tell you their limitations. And if they tell you it's not a good idea, it's not a good idea.
And they will tell you because they want you to call them back. If someone comes in and tells you it's going to be fine but doesn't tell you why it's gonna be fine, that's not a company you want to go with. That's for sure.
Have them explain to you the possibilities of what could go wrong, etc.
Also if you pump mud or foam under the house, make sure the company tests the plumbing system beforehand because you don't want that mud or foam getting into the plumbing system. Nobody should ever pump foam or mud under the house without having a plumbing test first.
And it's my recommendation that they run water through the system when they're pumping the foam even after they've checked to make sure there are no leaks.
When they are pumping the mud or foam, not only should they be running water through the whole system but that they also have a dedicated person watching the sewer system to make sure that nothing gets in there while they're doing it.
This is especially important if they're lifting the foundation. Anytime you lift and level a house, the possibility exists of pulling the plumbing pipes apart. Whether that be from putting in piers or from the mud/foam jacking.
You want to make sure nothing happens during the lifting process. That the lifting didn't create a leak even if there wasn't one beforehand.
A Few More Things to Keep in Mind
Whether you just got repair work done or you want to keep your current foundation safe, here are a few things to help you out with that.
Rain Water Drainage
You need to keep water away from the foundation.
Gutters will help with keeping water away from the foundation. If you've got a pooling spot around the foundation, even a small pooling spot, that's not good for the foundation at all.
You've got to keep excess water away from the foundation at all times. The expanding and contracting clay soil we have in D/FW can cause serious damage to your foundation.
Roots can also cause problems to foundations.
Consider getting a root barrier drilled into the ground. This is a barrier that is buried to keep those roots away from the foundation. It’s buried between the trees and the foundation.
Or if it’s an option you are OK with, cut down the trees. You've got to do something to keep roots out from under the house.
Roots grow to water. And they absorb a lot of moisture, a lot of water out from underneath the foundation.
Foundation Watering System
Something that helps to protect your foundation is a foundation watering system.
This is a fantastic video. It will tell you how to build your own foundation watering system.
Foundation watering systems keep your foundation consistently moist at the right amount of moisture. This prevents the soil from expanding and contracting against your foundation. It'll cost you a couple hundred bucks, and I highly recommend having one.
Wrapping It Up
As far as the pier types, a lot of people believe there are good things about all of them.
I'm personally a huge fan of drilled concrete and steel piers. And again, I will never use press pilings — ever — in a house I own. And helical I feel is overkill in most cases.
But I always recommend you find a good foundation repair contractor that you trust and go with what that person says. That is my general rule of thumb.
And remember, if you go cheap then you should count on paying more now and later when they put in extra piers. So be sure to keep that in mind.
All advice and opinions on DFW Foundation Repair are my own, Shawn Bucklew owner of In-House Plumbing Company, based on 20+ years of working with foundation repair companies.