calculate the cost of foundation repair

Calculate Slab Foundation Repair Costs: How Many Supports Do I Need?

You’ve heard nightmare stories about people being taken advantage of because they don’t have enough background knowledge on repair costs. You know that foundation repair can be expensive. But you don’t have enough info to estimate what is reasonably needed under your slab foundation to support it properly.

You are thinking: I don’t want anyone telling me I need more than I really do. I don’t want anyone making me pay more when I don’t have to. It’s hard to know who to trust.

Anchor Foundation Repair

At Anchor Foundation Repair, we have been assessing and repairing foundations for homeowners in Central Texas since 1985. We’ve determined how many supports are needed and estimated costs for thousands of homes through the years. We can give you a tip or two on how to estimate the number of supports needed for slab-on-grade foundation repair to give you ballpark costs.

Just so ya know, we do one type of slab foundation repair: drilled piers. However, this article will help you figure out a reasonable number of supports needed, no matter if they are pressed pilings, helical piers, steel pilings, or drilled bell-bottom piers like we use.

This article will review a few foundation repair basics to make sure you are in the right place. Then, we will show you how to calculate the number of supports you might reasonably expect to need in 4 easy steps. 

This will give you a general idea of how the number of supports is calculated and what your home could require before anyone comes out for a foundation inspection to give you a more exact estimate.

Foundation Repair Basics

Let’s cover just a few *foundational* things before we get to calculating. First, this article is written for slab-on-grade foundations only. Slab foundations do not have basements, and slab foundations do not have crawlspaces under them between the home and the ground. 

For more info on basic foundation types check out, “What Kind of Foundation Does My Home Have? 3 Common Types,”  if you are not sure what kind of foundation you have.

new slab foundation

Also, this article is written for the Central Texas area, where shallow slab foundations are prevalent and so is the expansive clay soil that these homes are commonly built on. We just want to make clear that some of this could be different if you live in another part of the country or state. Texas is big, y’all.

Lastly, when we say “foundation repair” what we are meaning is not caulking up cracks, or waterproofing things. We are talking about raising and leveling a settled slab foundation using underground supports. 

There are several methods of slab-on-grade foundation repair around, and they all use underground supports to lift your home back into the proper position. Some are called pilings, some are called piers, some are made of concrete, some are made of steel, and some are made of both materials.

4 Steps to Figure Out How Many Foundation Repair Supports You Need

Foundation Repair Plan

No matter what the supports are called or made of, these supports are all installed under the home vertically and are kind of like stilts supporting your home from underneath. 

These supports are spaced apart (i.e. they only put them in every so often). The number of supports contributes greatly to the cost of repair because pricing is calculated per pier or per pile. So, knowing about how many supports you need is key to calculating costs.

Let’s look at 4 easy steps to calculate how many supports you need for any basic slab-on-grade foundation repair method.

1. Draw and Measure the Footprint of Your Home

First, you’ll need a simple drawing of the footprint of your home and you need measurements for each exterior wall.

If you’re lucky, you might have a survey diagram from when you bought your home and can refer to it for measurements in feet. If not, grab a friend and some measuring tape (oh, and paper and pencil).

Draw a basic diagram of the shape of your house from a bird’s eye view and jot down the length in feet of each exterior wall. Your diagram doesn’t have to be perfect, just a basic shape with a number written on each side indicating its length. Here’s my house pictured.

foundation repair planning and estimating
Aerial satellite view, survey map, simple drawing

2. Determine Which Walls Are Affected by Settlement

Most of the time your whole home doesn’t need to be supported with foundation repair. It’s usually two walls that meet at a corner or three walls that surround the area of the home experiencing foundation settlement.

So it’s not usually the entire home, and it’s not usually needed under the interior of the home either. That’s not to say that an entire home doesn’t need foundation repair ever, or that supports are never needed under the interior of a home. 

About 30% of the homes we repair each year need the entire home supported, and about 10% of homes we repair each year need interior supports as well as perimeter support.

Right now, we are just trying to talk about fairly average home foundation repair needs and that’s usually either two or three adjoining walls needing support. There are a few examples pictured throughout this article. The blue dots show where supports are needed.

Go ahead and look at your home diagram, identify the two or three walls that seem to be experiencing problems or have signs of settlement or problems.

If you’re not clear on foundation settlement signs yet, no worries! Check out this article for help in what you are looking for: “Do I Have a Foundation Problems? Top 5 Signs Repairs Are Needed.” It’s usually things like diagonal cracks coming off of door, window, or cased opening frames, doors that don’t close, lock, or latch properly, or trim separating from walls.

true signs of foundation settlement

The exterior walls closest to where you are seeing these types of signs are likely the ones needing the extra support of foundation repair. These are the walls you will use to calculate the total linear feet in the next step.

3. Calculate The Linear Feet Affected by Settlement

Now you have identified the two or three perimeter walls likely to need foundation repair. Next, we need to add up the total linear feet of those sides. Basically, add up the length of those walls and get a total number of linear feet affected by foundation issues.

Total linear feet = add up the length of exterior sides needing support = TLF

What did you get? Remember that number for the next step.

4. Determine the Number of Supports Needed

With the total linear feet (TLF) now calculated, we can get to the good stuff of figuring out how many support piers or piles you need. In general, the number of support piers needed is every 7 linear feet along the affected walls of your home. 

calculate the cost of foundation repair

We’re going to take that total linear feet number and divide it by 7. If the number turns out to be a decimal, then you should round up to the nearest whole number. Always round up, don’t round down. Take that rounded number and add one to it to arrive at the number of piers you need.

TLF divided by 7 = Rounded Up Number

Rounded Number + 1 = Total # of Piers Needed

We could try to explain to you why you need to add a 1 to the rounded number, but your head might explode if we tried to explain it to you and it might just make things more confusing. So please just trust us on this . . . it’s a math thing . . . or a geometry thing . . . add the one and don’t try to understand why. Thank you for your understanding.

The good news is that now you know the total number of supports you might need for a perimeter slab-on-grade foundation repair job on your home.

Examples Calculating Supports Needed for Foundation Repair

Let’s do a couple of examples just to make sure you’ve got it down. We have put together two very basic scenarios you might see in a simple home that has experienced settlement on the corner of the house, and half the house or a section involving three sides.

Let’s take a look at each of our scenarios and determine the number of piers for each.

The Corner Problem

Total linear feet = 49 + 35 = 84

84/7 = 12 already a whole number

Add 1

Total number of supports needed = 13

True story, we wrote an article about a home with a corner problem sort of like this that we repaired. Check out Rosa’s foundation repair journey about her home built on a sloping lot. Rosa’s home had a “corner problem.”

The Section/Wing or Half-House Problem

Total linear feet = 28 + 42 + 28 = 98

98/7 = 14 already a round number

Add 1

Total number of supports needed = 15

Congratulations! You have determined how many piers are needed for these problem scenarios. If you haven’t already, it’s a good time to try this method out on your own home sketch since it is fresh in your mind. How many did you come up with?

The number of piers for a typical foundation repair job would probably fall between 15 to 25 supports (piers or piles) on average. How does this compare with your number? If your number is close, then you might have an average-sized foundation repair on your hands. If your number is higher or lower, then your job is likely bigger or smaller than the every day averages.

What is the Average Cost of Slab Foundation Repair?

The biggest determining factor in the cost of foundation repair is the number of supports needed. There are many*** other factors that contribute to the cost of foundation repair as well like the chosen method of repair, access limitations for where the supports are needed, and finishing services.

what is the average cost of foundation repair

Including all of these other factors along with the number of piers or piles, the average cost of foundation repair for 15 to 25 supports ranges between $7,500 and $20,000.

At Anchor Foundation Repair, we have found over the last 35+ years in business that 100% honesty is the best policy when it comes to cost and foundation repairs for your home. We don’t believe in hiding how we figure things and want you as informed and educated on the process as possible.

To that end, we “drill down” to more specifics on the average costs of foundation repair comparing the two most common methods of foundation repair available in our area. Check out, “Average Cost of Foundation Repair: Pressed Piles vs. Drilled Piers,” for the full story.


***Disclaimer Alert* Listen, determining where settlement is negatively affecting your home and the associated repair costs is really a job for a professional. 

There are a lot more cost and symptom factors to consider than just linear feet and a few walls. Since every home situation is very different, we’re just giving you some basic principles here which is all we can really do in an article. We are working on even more articles to cover more basic principles too!

Sometimes not an entire wall needs support, it could just be a portion of a wall and a portion of another wall. Who knows?! A foundation repair specialist knows. That’s where years of experience and expertise are needed to factor in all the other considerations for you. 

So, this article is for educational purposes only, not a way to get a guaranteed price for your foundation repair.