Window and Door Installation: Complete Guide

Overview

Installing windows and doors makes your house weathertight, protecting your investment from the elements and allowing interior work to proceed regardless of weather. Proper installation and flashing prevents 95% of water intrusion problems.

I've seen $15,000 in water damage from improperly flashed windows. Taking time to install correctly saves thousands in future repairs.

When This Phase Happens

Windows and doors install after roof is complete.

Must be complete first:

Can happen in parallel:

What comes after:

Should You DIY This Phase?

DIY If:

Hire Out If:

My recommendation: DIY with a helper. Window installation is straightforward but requires attention to detail. The biggest challenge is the weight - always have help lifting.

Most owner-builders successfully install their own windows, saving $2,000-$4,000 in labor. Take your time on flashing - that's where problems happen.

Materials Needed

Windows and Doors (2,000 sq ft home)

Windows and doors materials for a typical 2,000 sq ft home
ItemQuantityTypical CostNotes
Double-hung windows (30"x48")12-15 units$3,000-$6,000Vinyl or wood
Casement windows (24"x36")4-6 units$1,200-$2,400Bathrooms, specialty
Sliding patio door (6')1 unit$800-$2,000Entry to deck/patio
Entry doors (3'0" x 6'8")2-3 units$600-$3,000Front and back doors
Interior pre-hung doors8-12 units$800-$2,400Installed later

Installation Materials

Installation materials needed for window and door installation
ItemQuantityTypical CostNotes
Self-adhering flashing tape4-6 rolls$120-$200Critical for waterproofing
Foam backer rod200 LF$40-$60Seal gaps before caulk
Exterior caulk/sealant12 tubes$60-$120High-quality polyurethane
Cedar or composite shims50 bundles$100-$150Leveling and support
Exterior-rated screws5 lbs$40-$603" for nailing flanges
Spray foam (low-expansion)6-8 cans$60-$100Gap filling

Tools Required

Essential:

Nice to have:

Step-by-Step Process

Day 1-2: Preparation

Verify rough openings

Prepare openings

💡Pro Tip

The sill pan is the most important flashing detail. Water that gets past the window must drain out, not into your wall. I always install a sloped sill pan - it's $5 insurance against $5,000 in rot.

Day 2-4: Window Installation

Flashing sequence (this order matters!):

  1. Install sill pan (sloped away from interior)
  2. Apply flashing tape to sill, extending 6" up jambs
  3. Cut house wrap in "I" pattern around opening
  4. Fold house wrap inside opening and staple
  5. Apply flashing tape to jambs (bottom up, overlapping)
  6. Leave head flashing for after window installed

Window installation steps:

  1. Test fit - Set window in opening to verify fit
  2. Apply sealant - Bead of sealant on sill and jambs
  3. Set window - Lift window into opening from exterior
  4. Initial leveling - Level sill with shims at corners
  5. Plumb sides - Shim jambs until perfectly plumb
  6. Check square - Diagonal measurements should match
  7. Secure corners - Nail or screw top corners first
  8. Final shimming - Shim every 12" along jambs
  9. Check operation - Window should open/close smoothly
  10. Secure - Install all remaining fasteners per manufacturer
  11. Head flashing - Install flashing tape over head flange
  12. Lap house wrap - Fold house wrap back over flashing
⚠️Warning

Never over-shim windows. Over-shimming bows the frame and prevents proper operation. Snug is good, tight is bad.

Common window installation errors to avoid:

Day 5-6: Exterior Door Installation

Entry door preparation:

Door installation:

  1. Remove shipping bracing from door
  2. Apply sealant to sill and jambs
  3. Set door in opening
  4. Shim hinge side first - perfectly plumb
  5. Shim lock side - maintain even gap (1/8")
  6. Shim head - level
  7. Check door operation (should swing smoothly)
  8. Secure with 3" screws through hinges into framing
  9. Add screws at shim locations (every 12")
  10. Test operation repeatedly
  11. Apply head flashing
  12. Seal exterior gaps with backer rod and caulk

Patio door installation:

💡Pro Tip

Always test door operation before final fastening. Doors should open and close smoothly with no resistance. If they bind, check for twist in the frame (over-shimming is usually the cause).

Day 7: Sealing and Finishing

Interior air sealing:

Exterior sealing:

Final checks:

Code Requirements

Key IRC window and door requirements:

Subcontractor Considerations

If hiring window installers:

Typical pricing:

Timeline: 2-4 days for typical house

What to look for:

Common Mistakes

1. Wrong Flashing Sequence

Why it's a problem: Water gets trapped in wall, causing rot and mold. The #1 cause of window leaks. How to avoid: Follow proper sequence - sill first, jambs second, head last. Lap upper layers over lower. Cost if you don't: $3,000-$10,000 per window to repair rot and replace window.

2. No Sill Pan

Why it's a problem: Water that gets past window (it will) goes directly into wall framing. How to avoid: Always install sloped sill pan before window. This is non-negotiable. Cost if you don't: $5,000-$15,000 rot repair and window replacement.

3. Not Checking Level and Plumb

Why it's a problem: Windows don't operate properly, gaps in weatherstripping, locks don't engage. How to avoid: Use 6-foot level. Check multiple times during installation. Adjust shims carefully. Cost if you don't: Windows don't work, must remove and reinstall - $500-$1,000 per window.

4. Over-Shimming

Why it's a problem: Bows frame, prevents operation, breaks seals, voids warranty. How to avoid: Shim just enough to fill gap. Frame should be straight, not bowed. Cost if you don't: Window failure, replacement needed.

5. Wrong Rough Opening Size

Why it's a problem: Window doesn't fit, major reframing required or order new windows. How to avoid: Verify rough openings against window schedule before windows arrive. Order windows to match actual openings. Cost if you don't: $500-$2,000 per window to reframe or reorder.

6. Skipping Manufacturer Instructions

Why it's a problem: Installation doesn't meet code, voids warranty, may fail inspection. How to avoid: Read and follow manufacturer installation instructions exactly. Cost if you don't: Voided warranty, failed inspection, potential replacement.

7. Using Wrong Fasteners

Why it's a problem: Doesn't meet wind load requirements, fasteners rust, fail inspection. How to avoid: Use fasteners specified by manufacturer. Typically 3" exterior-rated screws. Cost if you don't: Failed inspection, window failure in high winds.

8. Poor Air Sealing

Why it's a problem: Energy loss, drafts, failed energy code compliance, uncomfortable home. How to avoid: Foam all gaps between window and framing. Spray carefully to avoid distorting frame. Cost if you don't: High energy bills, uncomfortable home, failed energy inspection.

Quality Checkpoints

Before moving to next phase, verify:

Budget Breakdown

Example for 2,000 sq ft home:

Budget breakdown for window and door installation
ItemCostNotes
**Materials**
Windows (15 units)$4,000-$8,000Vinyl double-hung
Patio door (1 unit)$800-$2,000Standard 6-foot slider
Entry doors (2 units)$1,000-$3,000Steel or fiberglass
Flashing materials$200-$350Tape, sealants
Shims and fasteners$140-$210Installation supplies
Spray foam$60-$100Gap filling
**Labor (if hiring)**$1,800-$3,30015 windows + 3 doors
**Total (DIY)****$6,200-$13,660**Materials only
**Total (Hired)****$8,000-$16,960**Materials + labor
💡Pro Tip

Windows are a long lead-time item (8-12 weeks typical). Order before you start framing to avoid delays.

Timeline Tips

Best season: Any season once house is weathertight (under roof)

Scheduling:

What Comes Next

After windows and doors:

  1. Siding installation - Complete exterior weatherproofing
  2. Rough-in trades - Plumbing, electrical, HVAC
  3. Exterior trim - Around windows and doors

Link to: Plumbing Rough-In Phase

Related Resources

Need Window Installation Help?

Proper flashing is critical to preventing water damage. If you're unsure about installation details, a consultation can save thousands in future repairs.