Shims

Three different tools get crammed into one product category, and that causes more bad installs than any other mix-up at the counter. Here’s the plain version. Shims are thin, tapered or flat spacers used to level, align, and support building components like doors, cabinets, and windows. Stakes and lath are something else entirely. Stakes are driven into the ground as reference markers, while lath creates support frameworks for materials like plaster or concrete.

Know which one you actually need before you grab a bundle. A shim levels a cabinet box. A stake marks a grade. A piece of lath frames out formwork. They don’t substitute for each other.

The single decision that determines whether your install stays level and lasts is matching the material to the moisture and the load. Get that wrong and you’re back on the job in a year.

What a Shim Actually Is, and the Sizes That Matter

A wood shim is a wedge-shaped piece of wood used to prop, adjust, hold, or tweak the position of an object. The wedges taper from less than 1/32-inch at their tip to ¼-inch at their thickest. That taper is the whole point — it lets you dial in a gap fine enough to land a door dead plumb.

Length matters more than people think. The ¼” x 1¼” x 7¾” is the most common size, popular for hanging doors, windows, and other gaps. The ¼” x 1¼” x 11¾” is also common, helpful for filling gaps over longer spans, such as for trim work, cabinets, and flooring applications. The longer length supports more material, as the slope is not as pronounced.

The longer shim isn’t just bigger. The gentler slope means it bears across more of the gap — which is exactly what you want under a cabinet run or along a flooring transition.

Size	Best for
¼” x 1¼” x 7¾”	Doors, windows, general gaps
¼” x 1¼” x 11¾”	Trim, cabinets, flooring — longer spans
8” cedar / 8” pine bundles	General leveling and shimming
8” composite (32/box)	Wet and moisture-prone work
12” cedar (42/bundle)	Long-span support
3.5” trim shim	Tight trim and finish work

Western Building Center’s shim lineup runs across that range — pine and cedar bundles, an 8” composite, a 12” cedar, and short trim shims for finish work, plus plastic and U-shim options for adjustment around fasteners.

Material Is the Whole Game in Montana

This is where the right call earns its keep. Pick the wrong material and freeze-thaw cycling or spring snowmelt does the rest.

For dry interior carpentry, wood is the workhorse. Wood shims are most often made from softwoods like pine or fir, as these are easy to cut and shave. The softer wood is less likely to snap and split when the installer drives a nail or screw through them.

Get near water and the rules change. Shims are also available in cedar, which are more useful for outdoor or wet applications as they’re less prone to rotting. Plastic shims are also available. Choose materials based on the environment: use wood (cedar preferred) for dry interior carpentry, plastic or composite for damp areas to prevent rot, and metal for high-load applications or heavy machinery.

Plastic and composite shims don’t care about moisture. Grove’s solid plastic shims come in color-coded sizes and solid thicknesses for easy alignment, and they won’t rot or rust. That matters for basements, bathrooms, exterior door jambs, and anywhere snowmelt finds its way in. A pine shim under a wet threshold swells, then rots, then drops the door out of plumb. A composite shim sits there for the life of the building.

Cedar earns its spot outdoors. Cedar products are valued for their exceptional resistance to decay and weathering, making them ideal for outdoor and indoor use. For stakes and lath that live in Montana weather, that rot resistance is the difference between one season and several.

Steel comes in for the heavy stuff. Use metal for high-load applications or heavy machinery, and verify load ratings for heavy items. Stone countertops, machinery bases — that’s where you stop trusting wood.

Stakes and Lath

Different jobs, different stock. Stakes go in the ground for layout and grade marking; lath frames out plaster, concrete formwork, and temporary bracing. Common applications include leveling, shimming, wedge support, formwork, and temporary bracing in lumber and construction projects.

Both come in graduated lengths so you can match the stake to the depth and the lath to the span. Stakes run 1x2 and 2x2 from 12” to 48”, and cedar lath comes in ¼” and 3/8” thickness in 1½” to 4’ lengths. For heavier wedge and bracing work, wood wedges in 2x4-12” handle the bigger support tasks.

Set cedar stakes outdoors. The same rot resistance that protects cedar shims protects a stake sitting in wet spring ground.

Installation Basics That Prevent Callbacks

The technique is simple, and skipping it is why doors sag. To install, gently tap shims into the gap with a hammer, check with a level, and trim excess flush.

Doors have a rule worth memorizing. Shim behind hinge locations to transfer weight directly to the frame. Skip that and the hinges carry load they were never meant to.

For filling gaps, work in pairs and don’t get greedy with the stack. When filling large gaps, avoid stacking more than two shims to prevent slippage; use pairs coming from opposite sides to maintain even thickness. The most common method is to stack them on top of each other in opposing directions, which creates a flat, parallel surface. To fill the gap, push or pull the ends toward or away from each other, adjusting the overall thickness of the stack.

For machinery, there’s a smarter move. Use slotted U-shims to adjust without removing fasteners.

And in wet or load-bearing spots, secure them for good. Don’t leave a shim floating behind a finish surface or under a load where it can creep.

Frequently Asked Questions

What’s the difference between a shim and a stake? A shim is a thin tapered spacer that levels and aligns building components — doors, windows, cabinets, trim. Shims level, align, and support components like doors, cabinets, and windows, while stakes are driven into the ground as reference markers. They’re not interchangeable.

Should I use wood or plastic shims in a bathroom? Plastic or composite. Use plastic or composite for damp areas to prevent rot. Wood swells and rots when it gets wet, and a bathroom — or a basement, or an exterior door jamb — eventually gets wet. Composite sits there and doesn’t move.

Why does cedar cost more, and is it worth it outdoors? Cedar resists decay and weathering, which is exactly what an outdoor stake or piece of lath needs. Cedar shims are more useful for outdoor or wet applications as they’re less prone to rotting. For anything living in Montana weather, that’s money well spent.

How many shims can I stack? Two, opposing each other. Avoid stacking more than two shims to prevent slippage; use pairs coming from opposite sides to maintain even thickness. More than that and the stack starts to creep.

What size shim is best for hanging a door? The standard ¼” x 1¼” x 7¾”. That’s the most common size, popular for hanging doors, windows, and other gaps. Set them behind the hinges so the load goes straight to the frame.

Can wood shims handle heavy loads like stone countertops? For the heaviest work, go to metal. Use metal for high-load applications or heavy machinery, and verify load ratings for heavy items. Wood handles lightweight to moderate tasks; stone slabs and machinery bases belong on steel.