Why Use Plastic Shims to Level Deck Stairs?

Plastic Wedges Won’t Rot Away and Will Bring You Up to Level

Plastic wedges are ideal for outdoor projects because while wooden shims are very cheap, they will not hold up to water exposure. Unless you live in an extremely arid climate any outdoor project will be exposed to water throughout the year, and water + wood = rot. That’s why we recommend using Wobble Wedges® for all of your outdoor projects. They are made from strong, durable plastic that can take +2,000 lbs of force, and no rot, guaranteed.

Because of the complicated math involved in making and installing deck stairs, there is a high likelihood that you will need to use plastic shims to get your stairs installed correctly. There are three common mistakes that could require shims to fix: making the tread tilt slightly to stop water accumulation, making the step height exactly the same, and fixing the angle where the stringers meet the deck.

Fix the Pitch of the Step (So it won’t accumulate water!)

Let’s say you cut your stringers and the tread angle tilts back to the riser, meaning that water could accumulate on the steps. They should have a very slight pitch down so that the water can run off. To fix this, place hard plastic Wobble Wedges® at the 90° corner of the stringer to bring the tread up slightly. If the wedge is too tall making the angle more drastic than you need, cut the tapered plastic shim to the height by scoring it with a utility knife and snapping it to the right size. When you attach the tread, be sure to place a screw through the location of the shim so that it will stay in place. For added security place a bead of subfloor glue under and on top of the wedge before securing it with a screw.

Fix the Step Height

Consistent step height is key to stair safety, even if your steps are only a ¼” off this can cause people to trip. Typically step height for stairs is between 6.5” and 8”, but it’s consistency that is key to stopping trips. If you’ve cut your stringers and realize you’ve cut too much off and now the steps will have a ¼ inch or more difference, you will need to use shims to fix it. If the angle you’ve cut on the stringer gives the step the right pitch, you can use two (or more) shims to bring the whole step up to the right height. Place hard plastic Wobble Wedges® along the length of the horizontal stringer to uniforming bring up the height of the step. Check that the level of the tread is correct, and then glue and screw the wedges in place.

Fill the Gap Between the Stringer and the Deck

Where the stringers meet your deck is another location that you might have to shim. If you’ve cut the wrong angle for the stringer to line up with the edge of the deck, you can use hard plastic Wobble Wedges to shim the gap between the stringer and the deck. Wobble Wedges® come in three sizes: BigGap™ wedges are .48” high, standard wedges are .25” high, and Mini wedges are .16” high. Choose the size that will fill the gap and cut off the excess shim. Glue and screw through the shim to hold it in place.