Why Is My Sill Plate Deteriorating?

Are you concerned about the wood at the bottom of your home? Sometimes it’s hard to tell if your home’s foundation is okay. Maybe the wood in your crawlspace looks like a warped painting from Jonah van Mullem. The wood connected to your footing has holes like the book and movie starring Shia LaBeouf cleverly named Holes.

Or maybe you’re thinking, “I think there’s an issue with my sill plating.” Maybe you’re not sure, but are doing your due diligence to investigate.

Regardless, there may be a chance your sill plates are deteriorating. If you want to know more about what to look for and why your sill plates are deteriorating, this article is for you.

Our team at Dalinghaus Construction has inspected more than ten-thousand homes across Southern California and Arizona, having done thousands of foundation repair projects. We’re experts who can see what is happening with your foundation and whether those sill plates are okay. So let’s get started on informing you. 

What are Sill Plates? 

Sill Plates are the pieces of wood attached to the footing of the home, anchoring the home to the foundation. It is made with either 2×4 or 2×6 pieces of wood set down horizontally. It’s the bolted in-between piece keeping the frame of your home attached to the footing so it won’t slide off the foundation.

You will find Sill Plates on Raised and Slab-on-grade Foundations.  

What causes my Sill Plates to deteriorate?

1. Moisture

Wood is like a sponge in the sense that it can absorb and lose moisture, causing it to expand and contract. Some parts of the wood will be affected more than others depending on where the water is concentrated. 

2. Termites/other insects

You may never see termites, but you will see the holes they create as they eat the wood from the inside out. What termites do is eat the cellulose from the wood. Unfortunately, they won’t stop eating. As they eat the wood, the piece will grow weaker and weaker. 

If it’s not termites, it may be bugs such as carpenter ants, which create tunnels in wood for their nest. These tunnels don’t have any debris. Greater damage is done to weaken the wood the longer carpenter ants are inside of a structure. 

If you happen to spot this damage from termites or other insects, call an exterminator. Most places won’t begin repairs until the threat is taken out. Replacing the wood doesn’t get rid of the problem, meaning it is likely the threat will still be present after the wood is replaced. There is no need to waste your money to have it replaced again in the future. Don’t even risk it if your Sill Plate will be replaced with treated wood. 

Will my house see deteriorated Sill Plates?

If you have an older home, it’s always a possibility. Houses weren’t being built with pressurized and treated wood back in the day as they do now. The wood used would inevitably deteriorate when exposed to the elements.

This isn’t to say Sill Plate deterioration won’t happen with new homes. Maybe someone forgot to pamper a plank of wood by asking about its hopes, dreams, and interests. That’s one way to know the wood hasn’t been treated well.

Or what actually happened is someone didn’t do the best job of injecting preservatives into the wood using high pressure. 

Either way, older homes are more prone to deal with Sill Plate deterioration. Though it’s not necessarily how old the home is; it’s whether moisture is getting in. 

What are signs to look for? 

-Check to see if the wood starts to look warped.


-Holes in the wood. 

The signs are visual. You (or a foundation inspector), would have to go into the crawlspace and see any issues. It’s not something you can see from upstairs. And you won’t be able to feel anything wrong with your sill plates from your first floor. If you can, you may have larger issues such as your sill plate completely disintegrating. 

If for whatever reason you are not able to go in that crawlspace, we would recommend you find someone to inspect those sill plates around every year or two. 

Dalinghaus Construction is willing to do a free evaluation of your home. It doesn’t have to be us, though. Go to whoever you might feel the most comfortable with. 

Are there areas that are generally more prone to deterioration such as the middle or corners?

Not really. It’s wherever water can build up. If a part of your wood reminds you of an episode of Spongebob Squarepants, that’s a good place to start looking. 

Does sill plate deterioration happen often? 

It’s not seen too often at Dalinghaus Construction. It isn’t very common, though we do go on a couple of inspections a week that involve sill plates.

Can I get this replaced on my own? Or do I need to hire someone?

Technically, you can fix the problem on your own, though it might not be cost-saving. The project will need an engineer to take a look at the project and it will need to be permitted. 

It will be a lot of effort with paperwork, as well as using special equipment and materials.

Overall, it depends on the work you would want to do. 

How can I make sure my sill plate won’t deteriorate in the future? 

Ensure there isn’t any moisture buildup, especially with water pooling or sitting on the wood. Be sure you have good ventilation and drainage. Prevent water from getting under your foundation. 

If you’re unsure about your sill plating or have any further questions, give us a call at 877-360-9227, or fill out our form for a free evaluation. Dalinghaus Construction is more than happy to help you with your foundation concerns.


Brian Dalinghaus

Brian is one of the Co-Founders of Dalinghaus Construction. He has been in the foundation repair industry since 2005. During his career, he has been associated with helping over 4,000 homes and structures throughout California and Arizona.

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