Measure Your Space
Accurate measurements of headroom, ridge height, and rafter angles determine what's possible in your attic conversion project.
Why Accurate Measurements Matter
Your attic measurements determine everything: whether you need dormers, where you can place rooms, how much usable floor space you'll have, and even if your attic is a good candidate for conversion at all. Inaccurate measurements lead to costly surprises during construction, design plans that don't work in reality, and potentially failed inspections. Taking the time to measure thoroughly now saves money and frustration later.
Tools You'll Need
Step-by-Step Measuring Guide
Measure Ridge Height (Peak)
The ridge height is your most important measurement - it determines maximum headroom:
- •Stand at the center of the attic beneath the ridge board
- •Measure from the top of the floor joists to the bottom of the ridge board
- •For finished ceiling height, subtract 6-8" for subfloor and ceiling drywall
- •Take measurements at multiple points along the ridge (roofs can sag)
Key Number: If your ridge-to-joist measurement is less than 8 feet, you may struggle to achieve 7-foot finished ceilings without modifications.
Map the Ceiling Height Profile
Create a height map to understand your usable space:
- •Starting from the ridge, measure down each slope every 2 feet
- •Mark where ceiling drops to 7 feet (minimum for habitable rooms)
- •Mark where ceiling drops to 5 feet (cutoff for countable floor area)
- •Note any obstructions: collar ties, purlins, or cross bracing
Pro Tip: Use painter's tape to mark the 7-foot and 5-foot lines on the rafters. This makes it easy to visualize your usable space.
Measure Floor Dimensions
Get the overall footprint of your attic floor area:
- •Measure total length along the ridge (end to end)
- •Measure total width from eave to eave across the joists
- •Note any irregularities: chimney chases, dormers, or bump-outs
- •Measure joist spacing (typically 16" or 24" on center)
Determine Roof Pitch
Roof pitch affects headroom and dormer planning. Two methods:
- Hold a level horizontally against a rafter
- Measure 12 inches along the level from the rafter
- Measure the vertical distance from that point to the rafter
- That distance is your "rise" - if 8", you have 8/12 pitch
- Place the angle finder on a rafter
- Read the angle in degrees
- Convert: 18.4° = 4/12, 26.6° = 6/12, 33.7° = 8/12, 40° = 10/12
Document Existing Features
Record the location of everything that will affect your layout:
Create a Scaled Drawing
Transfer your measurements to a floor plan:
- •Use graph paper with 1/4" = 1 foot scale
- •Draw the floor outline with overall dimensions
- •Mark the 7-foot ceiling height lines on each side
- •Shade the area with 7+ foot ceilings - this is your usable space
- •Mark all obstacles: chimney, vents, structural elements
- •Note the ridge line location
Interpreting Your Results
Excellent: Ridge 9+ feet, Pitch 9/12 or steeper
You likely have enough headroom for conversion without dormers. Focus on stair placement and layout optimization. This is the ideal scenario for a cost-effective conversion.
Good: Ridge 8-9 feet, Pitch 7-8/12
Usable but may benefit from one or more dormers to expand the 7+ foot ceiling area. Consider dormer placement carefully to maximize impact while controlling costs.
Challenging: Ridge 7-8 feet, Pitch 5-6/12
Dormers will likely be necessary. Shed dormers spanning most of one side may be the most cost-effective approach. Consider whether the investment is worthwhile.
Difficult: Ridge under 7 feet, Pitch under 5/12
Major modifications like raising the roof or adding large dormers would be required. Costs may approach or exceed a traditional home addition. Consult an architect.
Pro Tips
- ✓Take photos as you measure - they're invaluable for planning and discussions with contractors
- ✓Measure twice - mistakes on paper are much cheaper than mistakes in construction
- ✓Note the direction each measurement was taken from - it helps when creating drawings
- ✓A laser measure makes high measurements much easier and safer
- ✓Share your measurements with a structural engineer early - they can flag issues you might miss
Frequently Asked Questions
What is the minimum ceiling height needed for an attic conversion?▼
Building codes typically require a minimum ceiling height of 7 feet (84 inches) over at least 50% of the floor area. Areas with 5-7 foot ceilings can be used but don't count toward minimum area requirements. Spaces below 5 feet don't count as floor area at all.
How do I measure roof pitch in my attic?▼
Use a level and tape measure: hold the level horizontally against a rafter, measure 12 inches along the level, then measure the vertical distance from that point down to the rafter. If it's 6 inches, you have a 6/12 pitch. Alternatively, use a digital angle finder for quick, accurate readings.
What roof pitch is ideal for attic conversion?▼
A roof pitch of 9/12 or steeper is ideal for attic conversions, providing adequate headroom without dormers. Pitches of 7/12 to 8/12 may work but often benefit from dormers. Pitches below 7/12 typically require significant modifications like raising the roof or adding large dormers to create usable space.
How much usable floor space will I have?▼
Usable floor space depends on ceiling height. Calculate the area with 7+ foot ceilings by measuring where each roof slope drops below 7 feet. The space between these lines is your habitable area. Areas with 5-7 foot ceilings work for closets, storage, or knee wall spaces but don't count toward minimum requirements.