Plan Dormers
Expanding your attic's potential. Dormers add headroom where sloped roofs limit usability, bring in natural light, and transform cramped attic space into comfortable living areas.
Why Dormer Planning Matters
Dormers can transform an unusable attic into valuable living space, but they represent one of the biggest investments in an attic conversion. A well-designed dormer adds significant headroom exactly where you need it, brings in natural light that makes spaces feel larger, provides ventilation for comfort, and enhances your home's exterior appearance. A poorly planned dormer can waste money on minimal space gain, create awkward interior layouts, clash with your home's architecture, or cause water infiltration problems for years. The planning phase is where you make critical decisions about style, size, placement, and budget that determine whether your dormer investment pays off. Take time to understand your options, consult with professionals, and visualize the results before committing to construction.
What You'll Need for Planning
Step-by-Step Guide
Assess Headroom Needs
Determine where dormers would provide the most benefit:
- Map current ceiling heights across the entire attic floor
- Mark areas where ceiling drops below 7 feet (code minimum for habitable space)
- Identify where furniture placement is limited by low ceilings
- Note which rooms would benefit most from additional headroom
- Consider traffic flow - do you need headroom for hallways?
- Plan where windows and natural light would enhance the space
Planning Tip: Sketch your floor plan and shade areas where you can stand comfortably (7'+) versus crouch or crawl. This visual shows exactly where dormers would make the biggest difference.
Choose Dormer Style
Select the dormer type that best fits your needs and home style:
Shed Dormer:
- Pros: Maximum headroom gain, can span full roof width, most cost-effective per square foot
- Cons: Modern appearance may clash with traditional homes, may require design approval in historic districts
- Best for: Maximizing space in functional conversions, contemporary homes, back of house (less visible)
Gable Dormer:
- Pros: Traditional appearance, matches most home styles, adds architectural interest
- Cons: Less interior space than shed dormer, more complex to build, typically 6-10' wide max
- Best for: Street-facing elevations, Colonial/Cape Cod styles, when curb appeal matters most
Eyebrow Dormer:
- Pros: Distinctive appearance, subtle, adds light without changing roofline dramatically
- Cons: Minimal headroom gain, complex curved construction, expensive for space gained
- Best for: Decorative applications, historic homes, when light matters more than space
Size the Dormer
Determine optimal dormer dimensions:
Width Considerations:
- Gable dormers: typically 4-10 feet wide
- Shed dormers: can span 50-100% of roof
- Allow 6" minimum from roof edge
- Align with windows below when possible
- Consider structural rafter spacing
Height Considerations:
- Interior ceiling: 7' minimum at front
- Window height: allow for standard sizes
- Exterior proportion: match home scale
- Roof pitch: typically 4/12 to 8/12
- Don't extend above main roof ridge
Design Rule: Dormers generally look best when they don't exceed 50% of the total roof width and when the dormer roof doesn't rise above the main ridge. Oversized dormers look awkward and can create drainage problems.
Plan Window Placement
Design windows for function and aesthetics:
- Position windows to provide cross-ventilation with opposite wall openings
- If serving as egress, ensure minimum 5.7 sq ft opening, 24" height, 20" width
- Align dormer windows with windows on lower floors for cohesive look
- Consider room layout - windows at bed height for bedroom, higher for bathroom privacy
- Use multiple smaller windows vs. one large window for traditional look
- Plan for views - which direction offers the best outlook?
Energy Tip: South-facing dormers gain solar heat in winter but may overheat in summer. Consider window orientation and plan for appropriate shading or high-performance glazing based on exposure.
Get Engineering and Permits
Finalize plans with professional review:
Structural Engineering:
- Review roof structure and load paths
- Design headers spanning dormer opening
- Specify tie-in connections to existing roof
- Calculate snow/wind loads for dormer
- Provide stamped drawings for permit
Permit Process:
- Submit plans to building department
- May require design review board approval
- Check zoning for height restrictions
- Verify setback requirements (dormers add to building envelope)
- HOA approval may be required
Important: Never start dormer construction without permits. Dormers are highly visible changes that inspectors notice. Unpermitted work can require costly removal and creates problems when selling your home.
Pro Tips
- ✓Get contractor bids before finalizing size - a slightly smaller dormer might save thousands
- ✓Use photo editing software to mock up how dormers will look from the street before committing
- ✓Schedule dormer construction during dry season - open roof creates major leak risk during rain
- ✓Match siding, roofing, and trim exactly to existing home - mismatches look like afterthoughts
- ✓Consider one large shed dormer on the back of the house plus decorative gable dormers on the front
Frequently Asked Questions
What's the difference between shed, gable, and eyebrow dormers?▼
Shed dormers have a single flat roof sloping in one direction, maximizing interior headroom and space - ideal for functional conversions. Gable dormers feature a peaked roof forming an A-shape that matches traditional home styles, adding charm but less usable space than shed dormers. Eyebrow dormers are curved, wave-like projections that add character and some light but minimal headroom - they're primarily decorative. For attic conversions needing maximum space, shed dormers are most practical; for curb appeal with moderate space gain, gable dormers work well.
How much does a dormer cost to add?▼
Dormer costs vary widely based on style, size, and complexity. Expect $8,000-15,000 for a small gable dormer (4-6 feet wide), $12,000-20,000 for a medium gable dormer (8-12 feet), and $15,000-30,000+ for a full-width shed dormer. Factors affecting cost include: roof access difficulty, structural modifications needed, window quality, siding and roofing materials, and local labor rates. Adding multiple small dormers typically costs more than one large shed dormer covering the same area.
Do dormers need structural engineering?▼
Yes, dormers almost always require structural engineering review. Cutting into an existing roof removes rafters that are part of the structural system. An engineer must specify how loads will be transferred around the dormer opening, what headers are needed, how the dormer structure ties into the existing roof, and whether foundation or lower-floor modifications are required. Building departments typically require stamped engineering drawings for dormer permits.
Will adding a dormer change my home's exterior appearance significantly?▼
Yes, dormers significantly impact curb appeal - for better or worse depending on design. Well-designed dormers that match the home's architectural style enhance appearance and increase property value. Poorly proportioned or mismatched dormers can look awkward and reduce appeal. Key design considerations: match roof pitch to existing roof (for gable dormers), align windows with those on lower floors, use consistent siding and trim materials, and size proportionally to the roof - typically dormers shouldn't exceed 50% of roof width. Consider hiring an architect for design review.