You’ve got a crawl space home that needs leveling, and you’re picturing what a crew is going to use to hold it all up. You keep hearing the word shim . . . and now you’re wondering whether the material even matters. Why cedar? Isn’t there something else that is . . . sturdier??
At Anchor Foundation Repair, we’ve been leveling Brazos Valley crawl space homes since 1985, and I’ve personally bought more bundles of shims than I can even count. We don’t mind explaining exactly why we use what we use, because it’s your home on the line.
In this post, we’ll name the exact shim we use on crawl space and pier and beam homes, walk through the four purposes it serves, and lay out the honest pros and cons of cedar versus metal so you can see why we’ve landed where we have. By the end of this article, you’ll understand why we think these shims are the best choice for our house leveling repairs.
What Type of Shims Do We Use on a Crawl Space Home?
So what do we employ under your crawl space home when it’s time to level it? No need to bury the answer.
When it’s time to shim a pier and beam or block and base home, we use kiln-dried red cedar shingles. ONLY. No metal, no plastic, no exceptions on a crawl space job.
A cedar shim is a thin, tapered wedge of wood, roughly 8 inches by 16 inches. These are actually cedar shingles, the same kind sold often for siding, only we use them as shims instead. On your home, one or several are *wedged* in at the very top of the support stack or pier. They are inserted above the stacked concrete base and blocks that carry the load, and below the sill beams that flip the support structure to the horizontal.
The shims dial in the last bit of height so the space between the vertical stack and the horizontal beam is nice and snug. This close contact keeps your floor and foundation structure rattle-free and stable by making sure the load-bearing fully transfers down to the next piece of the structure and all the way to the ground.
We’re not anti-metal, by the way. We use steel shims all the time on slab foundations, where they’re the right call. But on a wood-framed crawl space home, cedar is the only material we trust, and the next two sections explain why.
Why Do We Use Cedar Shims? The 4 Purposes They Serve
So why cedar, specifically? It comes down to four jobs a shim has to do down there, and cedar handles every one of them well. We can absolutely explain why they’re the very best choice for your home.
A shim isn’t merely a space-filler. It has to fit a gap that’s not consistent across the top of every support station. It also has to spread real weight, stay workable in a tight space, and hold up for decades in a damp, sometimes insect-ridden area under your home. Here are the four purposes cedar shims serve, and the reason behind each.
1. The Tapered Edge Allows Precise Shimming
A cedar shingle is tapered, thin on one edge and thicker on the other. That wedge shape lets us tap it in exactly as far as the gap needs, hitting the right elevation with no guesswork. There’s no jumping between a few fixed thicknesses and hoping one lands close enough. We dial it in one tap at a time and one pier at a time because the spacing will be totally different for each one.
2. The Larger Size Delivers Maximum Support
A cedar shingle covers a lot of real estate. That broad footprint spreads the home’s weight across more of the wooden sill beam above and the support below. So, the load rides on the widest possible surface instead of bearing down on one small spot. This is in complete contrast to the small surface area of steel shims (more thoughts on steel shims below).
A larger pliable cedar shim also isn’t going to gouge into the wood the way a tiny one can.
3. The Light Weight Makes Cedar Easy to Work With
Cedar is light. A repairman can carry a bundle by hand and tap the shingles into place with a mallet, no heavy gear required. That matters more than you’d think in the cramped, low crawl spaces we often find ourselves in, where a foot of clearance is sometimes all you get. Cedar also gives a little, flexing along with the other wood in your foundation instead of fighting it.
4. Cedar Is Time-Tested and Proven to Last
This is the one that seals it. Cedar has held up homes for generations, and it earns that track record three ways.
Because our shingles are kiln-dried, most of the moisture is already baked out, so they shrink very little and hold their shape instead of pulling away from the gap down the road.
Cedar heartwood is also naturally resistant to rot, thanks to the oils in the wood, and those same oils make it unappealing to termites and other insects. In the damp, sometimes buggy world under a crawl space, those traits count for a lot.
I can’t *resist* putting this in a short easy list for you. The three ways cedar boosts longevity is through its natural:
- Shrink resistance,
- Rot resistance, and
- Wood-destroying insect resistance.
So here you have the perfect promotional tagline – Cedar Shims: precise, supportive, easy to handle, and built to last. Those four purposes are why cedar has been our crawl space shim of choice for decades, and why we don’t lose sleep over what’s holding your home up.
Cedar vs. Metal Shims: Why Don’t We Use Steel?
Some might know about steel shims used in foundation repair, so why don’t we recommend those? How does cedar stack up against steel in this case? You’ve already seen cedar’s strengths, so we’ll just name its two downsides: it costs more than metal (strange but true), and it can be harder to source in some regions.
Steel, by contrast, is strong and long-lasting and it’s our go-to on slab foundation repairs, but on a crawl space home its fixed thicknesses and small footprint can push humps into your floors and even crack support blocks (we’ve got a video showing this exact issue).
Here’s the balanced takeaway: metal isn’t the enemy, it’s just the wrong tool for this job. On a slab home, steel shims are a great choice and we use them without hesitation. On a wood-framed crawl space home, cedar’s precision, footprint, and natural durability win out. Same craftsman, different tool for the material at hand.
If you want the full head-to-head, we broke it down in Wood vs. Steel Shims on a Crawl Space Home: Which is Best?
Curious What Sits Under Those Cedar Shims?
Now you know the shim we choose for every crawl space home we level: a kiln-dried red cedar shingle, chosen for four solid purposes. It fits an exact gap, spreads the load, stays easy to handle in tight spaces, and holds up for the long haul against rot and termites. Cedar earns that spot over metal on a wood-framed home, plain and simple.
After 40+ years under Brazos Valley homes, we’d rather explain every choice we make than leave you guessing about your largest investment. The outcome we want for you: a level home, supported by materials that do their job, backed by a crew happy to talk through the how and the why. If you’d like us to take a look, our house leveling team is a call away.
We’ve covered the shim on top, but what about the stacked concrete base and blocks doing the heavy lifting right beneath it? That’s the real backbone of your support stack. See exactly what sits under those cedar shims in Top 5 Reasons Stacked Concrete Blocks Are Best for Crawl Space Homes.