A door that sticks, swings open on its own, or won't latch properly is almost always a shimming problem. Getting a door frame plumb and level during installation is the most important step for a door that operates correctly for years. Glazelock® composite plastic shims make the job easier and the results more durable than traditional wood shims. Made in the USA.
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What You'll Need
- Glazelock composite plastic shims
- Level (4-foot preferred)
- Hammer or drill
- Utility knife or oscillating tool (to score and snap shims)
- Finish nails or screws
Step-by-Step: How to Shim a Door Frame
Step 1: Set the Hinge Side First
The hinge side of the door frame is your reference point. Place shims behind the hinge locations — typically at the top hinge, bottom hinge, and middle hinge (if present). Use a level to confirm the hinge side jamb is perfectly plumb before fastening.
Step 2: Shim in Pairs
Always use shims in opposing pairs — one from each side — so the combined thickness is consistent and the frame doesn't tilt. Glazelock's interlocking tab design keeps shim pairs together during installation, preventing them from sliding apart.
Step 3: Check for Plumb and Adjust
After setting hinge-side shims, check plumb again with your level. Slide shims in or out to fine-tune until the jamb is perfectly vertical. Don't fasten yet — get it right first.
Step 4: Fasten Through the Shims
Once plumb, drive finish nails or screws through the jamb and shims into the rough framing. Glazelock plastic shims won't split when fastened through — a common problem with wood shims.
Step 5: Set the Strike Side
With the hinge side plumb and fastened, set the strike side jamb. Use shims to achieve the correct reveal (gap between door and jamb) — typically 1/8" on all sides. Check plumb and adjust before fastening.
Step 6: Score and Snap Excess Shim
Score Glazelock shims with a utility knife and snap off the excess flush with the jamb. The composite material snaps cleanly without splintering.
Step 7: Install the Head Jamb
Shim the head (top) jamb to achieve a consistent reveal across the top of the door. Check level and fasten.
Common Shimming Mistakes to Avoid
- Shimming only at fastener locations: Shim at hinge locations and anywhere the jamb needs support, not just where you're nailing
- Using a single shim instead of pairs: Single shims create a wedge effect that tilts the jamb
- Skipping the level check: Always check plumb before fastening — it's much harder to fix after
- Using wood shims in exterior doors: Wood absorbs moisture and can cause the frame to shift over time — use Glazelock plastic shims for exterior applications
Frequently Asked Questions
How many shims do I need for a door?
Typically 6–8 shim pairs per door — two per hinge location plus additional shims at the strike side and head jamb as needed.
Can I use plastic shims for exterior doors?
Yes — Glazelock composite plastic shims are moisture-proof and ideal for exterior door installations where wood shims would absorb water and cause the frame to shift.
How do I cut plastic shims?
Score with a utility knife and snap. Glazelock shims snap cleanly without splintering.
