How to Install a Door - Complete Prehung Door Guide
Professional door installation techniques for interior and exterior prehung doors. Learn proper shimming, leveling, weatherproofing, and hardware installation. Save hundreds on professional installation.
Dr. Snezana Lawrence
Mathematical Historian
15+ years experience
PhD from Yale University. Published mathematical historian ensuring precision in all calculations.
Education
PhD in Mathematical History - Yale University
Bruce Zawalsky
Survival & DIY Expert
28+ years experience
28+ years wilderness survival and hands-on construction experience. Author of "Canadian Wilderness Survival."
Education
Canadian Armed Forces Wilderness Survival Training
Quick Answer
Prehung door installation involves 8 main steps: check rough opening is 2-2.5" larger than door, install flashing for exterior doors, test fit door in opening, shim and secure hinge side jamb perfectly plumb, shim lock side for even 1/8" reveal gap, shim top jamb level, nail through all shims into framing, then install threshold, weatherstripping, casing trim, and lockset hardware. Key to success is patient shimming until door swings freely and reveal gap is consistent all around.
Project Overview
Time Required
Interior prehung door takes 2-3 hours for first installation including shimming, leveling, securing, and trim. Experienced installers complete in 1-1.5 hours. Exterior doors take 3-5 hours with flashing and weatherproofing. Replacing existing door is faster than new rough opening installation.
Difficulty Level
Moderate - prehung doors simplify installation but require patience for proper shimming and leveling. Key skills: reading level, shimming technique, and adjusting until door swings freely. Interior doors are beginner-friendly. Exterior doors require weatherproofing knowledge.
Cost Savings
DIY saves 50-70% vs professional installation. Interior prehung door: $150-400 materials, pro install adds $150-300 labor. Exterior door: $300-800 materials, pro adds $200-500. For standard interior door: DIY $150-400, professional $450-700. Save on labor and markup.
Types of Doors
Understanding door types helps you choose the right product and installation method for your project.
Interior Prehung Doors
Complete door unit with slab mounted in jamb, hinges installed. Most common and easiest installation. Jambs are typically 4-9/16" for standard 2x4 walls.
Pros:
- ✓Easiest installation
- ✓Hinges pre-mounted
- ✓No mortising needed
- ✓Jamb pre-assembled
- ✓Fastest option
- ✓Good for DIY
Cons:
- ✗More expensive than slab
- ✗Requires correct rough opening size
- ✗Heavier to maneuver
New construction, room additions, replacing old doors, DIY projects
2-3 hours first time, 1-1.5 hours experienced
Exterior Prehung Doors
Heavy-duty prehung door with weather-resistant jamb, threshold, and weatherstripping. Often includes brick mold trim. Typically 1-3/4" thick (vs 1-3/8" interior).
Pros:
- ✓Complete weatherproofing system
- ✓Pre-bored for lockset
- ✓Threshold included
- ✓Energy efficient
- ✓Brick mold trim attached
Cons:
- ✗Heavy (80-100+ lbs)
- ✗Complex flashing required
- ✗More expensive
- ✗Challenging alignment
- ✗Weather-dependent install
Front doors, back doors, garage entry, any exterior opening
3-5 hours including flashing and weatherproofing
Door Slabs (Slab Doors)
Door only, no jamb or hardware. Requires existing jamb or building new jamb, installing hinges, boring holes for lockset. For experienced installers.
Pros:
- ✓Lower cost
- ✓Replacement without changing jamb
- ✓More style options
- ✓Lighter to transport
Cons:
- ✗Requires mortising hinges
- ✗Must bore lockset holes
- ✗Harder to get perfect fit
- ✗More skill needed
- ✗Time-consuming
Replacing damaged door in good jamb, custom installations, experienced carpenters
3-5 hours for slab-only installation with new jamb
Tools & Materials Needed
Tools
Measuring & Leveling
- •4-foot level (essential)
- •Tape measure
- •Carpenter's square
- •Pencil
Fastening & Cutting
- •Hammer or finish nailer
- •6d and 8d finishing nails
- •Drill with bits (lockset installation)
- •Utility knife (cutting shims)
- •Handsaw or jamb saw
Installation Tools
- •Shims (cedar or composite)
- •Pry bar
- •Nail set for countersinking
- •Clamps or door wedges
Exterior Door Add-ons
- •Caulk gun with exterior caulk
- •Flashing tape
- •Sill pan
- •Oscillating saw
- •Weatherstripping (if not included)
Materials
| Material | Specification |
|---|---|
| Prehung door | Interior or exterior, correct hand/swing 1 complete unit |
| Shims | Cedar or composite, 8" long 1 bundle (12-16 pairs) |
| Finishing nails | 6d (2") and 8d (2.5") 1 small box each |
| Door casing | Matches interior trim, 2-1/4" typical 17-20 linear feet per door |
| Threshold | Exterior doors (often included) 1 per exterior door |
| Weatherstripping | Compression or V-strip 17 linear feet (perimeter) |
| Exterior caulk | Paintable, flexible 1-2 tubes for exterior |
💡 Pro Tip: Measure your rough opening before purchasing door. Most common mistake is buying wrong size door.
Door Components
Understanding each component helps you install doors correctly and troubleshoot issues.
Door Slab
The actual swinging door panel, typically 1-3/8" thick (interior) or 1-3/4" thick (exterior). Made of solid wood, hollow core, solid core, or fiberglass.
Provides privacy, security, climate control, and sound dampening between spaces
Door Jamb (Frame)
Three-piece frame (two side jambs and head jamb) forming the door opening. Interior jambs are 4-9/16" for 2x4 walls, exterior jambs are thicker.
Supports door, provides mounting for hinges and strike plate, creates weathertight seal
Hinges
Typically 3 hinges for standard door (3.5" x 3.5"), mortised into door edge and jamb. Exterior and heavy doors use 4" hinges.
Allow door to swing open and closed, support door weight, control swing alignment
Threshold (Sill)
Horizontal piece at bottom of door opening, usually oak or aluminum. Exterior thresholds slope outward for water drainage.
Provides transition, prevents drafts, sheds water, adjusts for floor height differences
Weatherstripping
Compression gaskets or V-strips attached to door jamb and threshold creating airtight seal when door closes. Critical for exterior doors.
Prevents air and water infiltration, improves energy efficiency, reduces drafts and noise
Strike Plate
Metal plate mortised into jamb where latch bolt engages. Secured with long screws into framing for security.
Receives door latch, provides security, prevents jamb damage from repeated latching
Door Casing (Trim)
Decorative molding around door jamb covering gap between jamb and wall. Typically 2-1/4" to 3-1/2" wide matching other interior trim.
Covers shimming gaps, provides finished appearance, protects jamb edges from damage
Brick Mold (Exterior Trim)
Exterior trim around door on outside of house, typically 2" thick wood or PVC. Often pre-attached to exterior prehung doors.
Covers gap, provides mounting for siding, creates decorative exterior frame, weather protection
Step-by-Step Installation Guide
This guide covers installing a prehung door in a properly sized rough opening. Patience with shimming is the key to professional results.
Check and Prepare Rough Opening
Proper rough opening size and condition is critical for successful door installation. Fixing issues now saves frustration later.
Key Tips:
- ✓Measure rough opening width and height at multiple points (openings aren't always perfect)
- ✓Opening should be 2-2.5" wider than door width, 2.5" taller than door height
- ✓Check jambs for plumb with level - should be within 1/4" over full height
- ✓Verify opening is square by measuring diagonals - should be within 1/4" of equal
- ✓Check floor is level across opening - shim or level as needed before door installation
- ✓Remove old door, nails, shipping, debris - clean opening thoroughly
Too-small rough opening cannot be fixed easily. May require removing drywall and reframing.
Install Sill Pan and Flashing (Exterior Doors Only)
Proper flashing prevents water damage and rot. This step is critical for exterior door longevity.
Key Tips:
- ✓Install sill pan sloping toward exterior (1/4" drop over 36" width minimum)
- ✓Sill pan should extend 3-4" up jamb sides and wrap corners
- ✓Apply flashing tape to jack studs on both sides before door installation
- ✓Ensure any house wrap or building paper laps over flashing properly
- ✓Test drainage: pour water on sill pan, verify it flows out not into house
- ✓Some prehung exterior doors include integral sill pan - check before installing separate one
Improper flashing causes hidden water damage and rot. This is #1 cause of exterior door failure.
Test Fit and Inspect Prehung Door
Verify door condition and fit before committing to installation. Easier to return damaged door before nailing.
Key Tips:
- ✓Remove shipping packaging carefully - inspect for shipping damage before discarding box
- ✓Check door swings freely on hinges - should move smoothly without binding
- ✓Verify reveal gap (space between door and jamb) is consistent on all sides
- ✓Test fit door in opening - jamb should fit with 1/4-1/2" gap on sides and top
- ✓Remove cardboard spacers at bottom of jamb legs (interior doors) but keep until shimmed
- ✓Verify door swing direction matches your needs (left-hand vs right-hand swing)
Once you nail door in place, returning it becomes difficult. Inspect thoroughly first.
Shim and Secure Hinge Side Jamb
Hinge side must be perfectly plumb. This side controls entire door operation - take your time.
Key Tips:
- ✓Place door in opening, tip jamb into place carefully (get help for heavy doors)
- ✓Insert shim pairs behind hinge side jamb at each hinge location (typically 3 hinges)
- ✓Check jamb plumb with 4-foot level along entire height - adjust shims until perfect
- ✓Shims should be snug but not bowing jamb - door should swing freely
- ✓Drive one 8d finishing nail through jamb and shims into framing at each hinge
- ✓Don't fully sink nails yet - leave room for adjustment if needed
Out-of-plumb hinge side causes door to swing open or closed by itself. Must be perfectly plumb.
Shim and Adjust Lock Side Jamb
Lock side sets door gap and ensures smooth closing. Adjust until reveal is consistent and door latches properly.
Key Tips:
- ✓Close door and check reveal gap - should be even 1/8" between door and jamb all the way down
- ✓Insert shim pairs behind lock side jamb at top, middle, and bottom (plus at strike plate)
- ✓Adjust shims until reveal gap is consistent - may need to adjust hinge side slightly
- ✓Check door closes smoothly and latches without forcing - adjust shims if binding
- ✓Ensure lock side jamb is same distance from hinge jamb at top and bottom (parallel)
- ✓Nail through jamb and shims with 8d finishing nails when gap is perfect
Uneven reveal gap means door won't close properly or seal correctly. Take time to get this right.
Shim and Secure Top Jamb (Head)
Top jamb completes door frame and ensures consistent reveal gap at top of door.
Key Tips:
- ✓Check top reveal gap with door closed - should match side gap (1/8")
- ✓Insert shim pairs at center of top jamb and about 12" from each corner
- ✓Verify top jamb is level - slight variance is OK as long as reveal is even
- ✓Don't over-shim top jamb - can bow it down and cause door to bind
- ✓Nail through jamb and shims into header framing with 8d finishing nails
- ✓Open and close door several times - should move freely without catching
Over-shimming top jamb bows it and causes door to bind at top. Shim just enough to secure.
Final Fastening and Shim Trimming
Secure all shim points permanently and trim shims flush for professional appearance.
Key Tips:
- ✓Add additional shim pairs every 12" along jambs for security and preventing bow
- ✓Drive 8d finishing nails through jambs into framing at all shim locations
- ✓Set nails slightly below surface with nail set (will be filled later)
- ✓Test door operation - open, close, latch multiple times confirming smooth action
- ✓Score shims with utility knife where they meet jamb, snap off excess
- ✓Cut remaining shim ends flush with jamb using handsaw or oscillating saw
- ✓Leave shims long behind hinge jamb if installing thick casing (1/2" reveal)
Don't over-drive nails. Sinking too deep can pull jamb and change door alignment.
Install Threshold, Weatherstripping, Trim, and Hardware
Finishing touches complete installation and provide professional appearance.
Key Tips:
- ✓Install or adjust threshold at bottom - should be tight to door bottom with slight compression
- ✓Apply weatherstripping if not pre-installed - compression type around jamb, sweep at bottom
- ✓Install door casing around jamb - miter corners at 45°, nail to jamb and wall framing
- ✓Casing should have 1/4" reveal (setback) from inside jamb edge for professional look
- ✓For exterior: caulk between brick mold and siding, around threshold
- ✓Install lockset and deadbolt according to manufacturer instructions
- ✓Adjust strike plate if needed for smooth latching - may need to file or shim
- ✓Install door stop (if not integral to jamb) so door sits flush when closed
Exterior caulking must be complete before first rain. Water infiltration causes immediate damage.
Common Mistakes to Avoid
| Mistake | What Happens | How to Fix/Avoid |
|---|---|---|
| Not checking rough opening size | Door doesn't fit, requires drywall removal and reframing to fix | Measure opening before buying door - width + 2.5", height + 2.5" |
| Hinge side not plumb | Door swings open or closed by itself, won't stay in position, gaps develop | Use 4-foot level on hinge jamb, must be perfectly plumb |
| Uneven reveal gap | Door binds, won't close, latch doesn't align, poor seal, unprofessional appearance | Adjust shims until gap is consistent 1/8" on all sides |
| Over-driving nails | Pulls jamb out of alignment, changes reveal gaps, difficult to adjust later | Sink nails just below surface, don't overdrive into jamb |
| Forgetting exterior flashing | Water infiltration, rotted framing, failed door, costly repairs | Always install sill pan and flashing tape before door on exterior |
| Wrong door swing direction | Door blocks light switches, furniture, traffic flow - expensive to replace | Verify swing direction before ordering - consider room layout |
| Not securing to framing | Door sags over time, gaps develop, eventually fails | Nail through shims into solid framing every 12", use long screws at strike |
| Installing in wrong size opening | Too big: door won't fit. Too small: insufficient shimming space, weak install | Standard door + 2-2.5" width and + 2.5" height for rough opening |
When to Hire a Professional
While standard prehung doors are DIY-friendly, these situations benefit from professional installation:
Solid core or oversized exterior doors
Heavy doors (100+ lbs) require two people minimum, special handling, and experience with weight distribution. Fiberglass and solid wood exterior doors are especially heavy and expensive to damage.
Complex trim or historic restoration
Ornate casings, rosette blocks, plinth blocks, or matching historic trim requires advanced carpentry, specialized tools, and experience with traditional methods. Mistakes ruin expensive custom millwork.
Door rough opening issues
Out-of-plumb walls, wrong size openings, structural damage, or non-standard sizes require reframing, drywall work, and carpentry experience. DIY attempts often make problems worse.
French doors or double doors
Paired doors require precise alignment, astragal installation, coordinated hardware, and careful shimming. Getting both doors to close evenly and seal properly is challenging.
Exterior doors in severe climates
Extreme weather requires perfect flashing, specialized weatherstripping, proper drainage, and understanding regional building codes. Mistakes cause immediate problems in harsh conditions.
Security doors or commercial doors
Heavy-duty security hardware, commercial-grade hinges, fire-rated doors, and ADA-compliant installations require professional knowledge and may need inspection/certification.
💵 Professional Installation Costs
- • Interior door labor: $150-300 per door
- • Exterior door labor: $200-500 per door
- • Interior door total (materials + labor): $300-700
- • Exterior door total (materials + labor): $500-1,300
- • French doors or doubles: Add 50-100% for complexity
Frequently Asked Questions
Can I install a door myself?
Yes, installing a prehung interior door is a manageable DIY project for intermediate skill levels, taking 2-3 hours. Exterior doors are more challenging due to weatherproofing requirements but still DIY-able with patience. The key skills are shimming, checking level/plumb, and adjusting until door swings freely. Prehung doors are much easier than slab doors since jamb and hinges are pre-assembled.
What is a prehung door?
A prehung door comes with the door slab already mounted in a door jamb (frame) with hinges installed. You install the entire unit as one piece into the rough opening. Prehung doors are easier to install than slab doors (door only) because alignment is pre-set and you don't need to mortise hinges or drill holes. Most new construction uses prehung doors.
What size rough opening do I need for a door?
Rough opening should be 2-2.5 inches wider than door width and 2.5 inches taller than door height. For a standard 36" wide x 80" tall door, rough opening is 38-38.5" wide x 82.5" tall. This allows space for door jamb plus 1/4-1/2" shimming gap on each side. Exterior doors may need slightly larger openings for thicker jambs.
How do you shim a door properly?
Start with hinge side: place shim pairs behind jamb at each hinge, check plumb with level, nail through shims. Then shim lock side: close door, check for even 1/8" reveal gap, adjust shims until gap is consistent and door swings freely. Finally shim top jamb at center and corners. Always use pairs of shims (opposing tapers) and nail through shims into framing.
What tools do I need to install a door?
Essential tools: 4-foot level (checking plumb/level), tape measure, hammer or finish nailer, shims, finishing nails (6d and 8d), utility knife (cutting shims), pry bar, drill with bits (for lockset). Optional but helpful: jamb saw for trimming jamb legs, oscillating saw for casing cuts, nail set for countersinking nails. Most are common household tools.
What is the difference between interior and exterior door installation?
Interior doors are simpler: no weatherproofing needed, lighter doors, standard jambs. Exterior doors require: sill pan and flashing installation, threshold with weatherstripping, heavier duty hinges, deadbolt preparation, exterior-grade caulking, proper drainage slope, and often brick mold trim. Exterior doors must seal against weather while interior doors just need to close smoothly.
How much gap should be around a door?
The "reveal" gap between door and jamb should be consistent 1/8" (3mm) on top and lock side, slightly larger at bottom (1/4-3/8" for carpet clearance). Hinge side has minimal gap since hinges control spacing. Uneven gaps indicate door isn't shimmed properly. Gap allows door to expand with humidity changes without binding.
How long does it take to install a door?
Interior prehung door: 2-3 hours for first-timers, 1-1.5 hours for experienced DIYers. Exterior door: 3-5 hours including flashing and weatherproofing. Replacing existing door in good opening is faster than new installation. Time includes removing old door (if applicable), shimming, securing, installing trim, and hardware. Complex issues with rough opening add time.
Related Resources
This guide has been reviewed by multiple experts to ensure both technical accuracy and practical application.
Dr. Snezana Lawrence
Mathematical Historian | PhD from Yale
Dr. Lawrence is a published mathematical historian with a PhD from Yale University. She ensures mathematical precision and accuracy in all our calculations, conversions, and academic score calculators. Her expertise spans computational mathematics and educational assessment.
LinkedIn ProfileBruce Zawalsky
Survival & DIY Expert | 28+ Years Experience
Bruce is a wilderness survival expert with 28+ years of experience and author of "Canadian Wilderness Survival." His extensive hands-on experience in building wilderness shelters, construction projects, and practical DIY work, combined with his military training, ensures all our construction guides and survival content are field-tested and practical.
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