Main Sill

Crawl Space Foundation Homes: What Is a Main Sill and What Do They Do?

You’re looking at some crawl space foundation repair resources or paperwork and have come across the term main sill. What in the world is a *main sill* and what does it do for your home? And while we’re at it, why does it need to be repaired?

Anchor Foundation Repair Bryan College Station

At Anchor Foundation Repair, we understand that new and confusing industry-specific terminology can leave homeowners feeling at a disadvantage. We hate it when contractors don’t take the time to explain these foreign terms and can certainly define this *home part* for you. We work with sills of all kinds all the time, it’s a big part of our work with crawl space homes

We don’t want anyone to have unanswered questions about their house leveling proposal for foundation repair. Your proposal might be the first time you have seen this term. We thought of you when writing this article.

This article will define and explain the term “main sill” and its role in the foundation of your crawl space home. We will discuss why the main sills need to be replaced and how it’s done. You will understand what needs to be done to repair your home and why it’s beneficial.

What Does a Main Sill Do For My Crawl Space Foundation?

Main sill beams are a key component of any crawl space home in both pier and beam and block and base types of foundations. Sills in crawl space homes are large, long, and strong beams (typically made from wood on this home type) that help carry the weight of your home.

Types of Sill diagram
Brown lines = Main Sill

For block and base homes, main sills are found along the perimeter of the home and follow its footprint outline. Main sill beams span the distance between vertical piers and run underneath load-bearing walls in all types of crawl space foundations. What sills *do* is allow the structure to move from a vertical orientation with the piers to a horizontal orientation by bridging the gaps between piers.

Think of your crawl space or pier and beam foundation like a layer cake – or maybe since we’re in Texas like a 7-layer dip. (aaaand now I’m hungry . . . )

From the ground up, the layers go like this:

  1. Dirt/Soil/Ground
  2. Piers that elevate the home and transition up from the ground to the sill beams,
  3. Shims are inserted between the sill and piers to make small elevation adjustments and keep things as level as possible,
  4. Sill beams that hold up and support the floor joists,
  5. Floor joists that support the subfloor and the home structure,
  6. Subfloor that serves as an underlayment for your finished flooring surface, and
  7. Floor transitioning to framing and walls.

Why Does My Main Sill Need To Be Replaced?

Since sill are most often made from wood material, they are subject to deterioration over time. Sometimes a sill just gets too old under an old, old home, but more likely there’s a culprit to blame like,

replacing main sill beam

All of these issues are very common and likely in our area. Termites like moisture, and there’s usually plenty of moisture under Texas crawl space homes, whether from air humidity, ground vapor, or poor drainage.

These conditions lead to curved, warped, wavy, and crumbling sills. The beams start to fail and begin to affect the alignment of doors, floors, and other common signs of foundation issues with pier and beam homes. Replacing your main sill beams as part of your house leveling project will correct these problems.

How Are Main Sill Replaced on a Pier and Beam Home?

With the main sills being such a large component of your home’s foundation, their replacement is important to carry out carefully. 

Extra attention should be paid to this task when you’re essentially pulling something out of the middle of the *7-layer dip* and leaving the other layers there. A foundation repair contractor needs to maintain the alignment and structural integrity of all the other layers during the removal and replacement of a sill beam.

Here’s how a main sill replacement is done:

  1. Temporarily support the home by placing an offset beam running in the same direction as the failing sill,
  2. Cut out or remove the damaged beam or beam section,
  3. Install a new 4 x 6” pressure-treated sill beam in the same location as the old beam, and
  4. Use shims to secure on top of the original piers.
how are main sills replaced on pier and beam home?

The new sill must be installed in the exact location of the original sill. If the sill was under a wall before, it must be under the wall again. You can’t *sister* sill beams and place a new one adjacent to an old one and bind them together. Sistering doesn’t work for sill beams. Only the precise replacement in the original sill position will do.

How Does a New Main Sill Benefit My Home and Foundation?

If you need new main sills, you should want them. Sills are beneficial and essential for the proper functioning of your pier and beam foundation. Replacing your main sills improves your home in these ways:

home foundation repair
  • Making doors operational again,
  • Eliminating gaps between floors and walls, 
  • Closing cracks in your walls, and
  • Returning your home to a sturdy and stable condition.

This is what foundation repair is all about for your crawl space home – everything working right and being well-supported so you can get on with enjoying life.

Ready to Get Your Crawl Space Home Repaired Now?

Now that you know all about the importance of main sills, what they do, and how they are fixed, what’s next? Well, if you’ve already got a proposal for foundation repairs with Anchor, go ahead and accept that proposal to get your job started as soon as possible.

repair sill beams on crawl space home

Be the hero of your household by getting your Brazos Valley foundation repaired with Anchor. Elevate your home, preserve your peace of mind, and rest easy with Anchor’s 35+ years of experience, careful workmanship, and top-notch service.

Maybe you’re still just learning about your crawl space foundation and aren’t ready to get started – that’s okay too. How about what’s next in this 7-layer dip we keep talking about? Above the main sills you will find the floor joists. Here’s the rundown on floor joists complete with their definition, purpose, and problem indicators.