Converting unused space above a garage into a usable attic or storage area can add valuable square footage to a home. With some planning and elbow grease, this type of garage attic conversion project can be manageable for a dedicated DIYer. Here’s what you need to know about the feasibility, costs and process of adding an attic over a detached garage.
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Is it possible to add an attic over a garage?
In many cases, it is possible to add an attic space over an existing detached garage. There are a few key factors to consider:
Garage framing and structure
The existing garage structure and framing must be able to support the additional weight and forces of an attic build-out. Most modern garages built from the 1990s onward should have the needed structural capacity. Older garages may require additional framing reinforcement and foundation work to support an attic conversion. Consult with a structural engineer to evaluate feasibility.
Roof pitch and space
The roof pitch and shape over the garage is important. For sufficient headroom, the roof pitch needs to be sufficiently steep to allow for attic floor joists and usable space. Typically a minimum pitch of 4/12 is recommended, but the steeper the better for maximizing space. The overall dimensions and footprint of the garage also determine how much attic space can be added.
Zoning laws and codes
Most areas allow the addition of attic space over detached garages, but zoning laws should be checked for any restrictions. The conversion must meet local building codes for structural requirements, energy efficiency, permits and more.
Accessibility
Adding stairs or a pull-down ladder are two options for accessing the new attic space. The existing garage plans should accommodate an access point and stairs.
Garage Attic Conversion Costs
Converting a garage attic averages $50 to $100 per square foot for a simple low-budget DIY project up to $150+ per square foot for a more complex professional build with finishes.
Here are typical price ranges for key elements:
Framing and labor
– Framing materials (lumber, etc): $5-10 per square foot
– Framing contractor labor: $5-10 per square foot
Roofing
– Removing and replacing roof: $4-8 per square foot
– Roof trusses or rafters: $8-12 per square foot
Insulation
– Batt insulation: $1-1.50 per square foot
– Spray foam insulation: $3-4 per square foot
Drywall
– Drywall materials and supplies: $2-3 per square foot
– Drywall installation labor: $1-2 per square foot
Access ladder and door
– Pull-down ladder: $150-300
– Access door: $150-300
– Stairs (if space allows): $1000-2000
Permits, drawings and fees
– Permit fees: $200-600
– Architectural drawings: $1000-2000
So a 500 square foot garage attic conversion could run $25,000 to $50,000+ on average for a mid-range quality build. The economy and customization of finishes make a big impact on overall garage attic costs.
DIY vs Hiring a Contractor
For homeowners with construction experience, a DIY garage attic conversion is possible. But due to the complex structural work involved, hiring a general contractor is recommended for most conversions.
Benefits of DIY conversion:
– Cost savings – DIY provides large potential cost savings
– Control – Complete control over the project and decision making
– Satisfaction – Sense of accomplishment doing the work yourself
Benefits of hiring a contractor:
– Expertise – Contractors have the specialized structural, roofing and finishing skills needed
– Efficiency – A contractor crew will complete work much faster than DIY
– Warranty – Professional work often comes with guarantees and warranties
A contractor may still involve some DIY elements like demolition, insulation, drywall and paint which can save money. But for the core structural work, a general contractor is advisable unless the homeowner has extensive framing experience.
Steps for Converting a Garage Attic
Here is an overview of the typical process for adding an attic over a garage:
Planning and permitting
– Assess the existing garage structure and roof for feasibility.
– Have an engineer evaluate and provide recommended plans for structural reinforcement.
– Draw up attic floor plans detailing the layout and access stairs/ladder.
– Apply for all required permits with the municipality.
Prepping the garage
– Remove any items stored in the garage to clear space.
– Install temporary shoring posts and supports for the existing roof structure.
– Detach the garage from the home if it shares a wall to work independently.
Framing the attic
– Remove garage roof shingles/materials down to the rafters or trusses.
– Reinforce existing trusses and wall structures as needed per plans.
– Install new trusses or rafters sized for the attic space.
– Add collar ties, gussets and supports to connect and strengthen the new framing.
– Frame floor joists across the bottom of the rafters/trusses.
– Frame and cut out openings for the access stairs or ladder.
Closing it in
– Install plywood sheathing over the new rafters and floor joists.
– Replace any garage roofing materials removed like underlayment, drip edge, shingles.
– Add roof vents as needed for proper attic airflow and moisture control.
Finishing the interior
– Run electrical wiring and add boxes, lights and outlets as desired.
– Insulate the attic floor and walls thoroughly.
– Install an attic access ladder or staircase.
– Drywall over walls and ceiling areas. Mud, tape and finish drywall.
– Prime and paint.
– Optionally add flooring, storage systems or furnishings.
Completing exterior
– Patch or replace siding on garage gable ends extended upward for the attic space.
– Install rain gutters and extend downspouts if needed.
– Paint or finish the garage to match house exteriors.
Building Permits and Codes
Nearly all garages attic conversions will require building permits because structural work is involved. The scope of the project will determine the specifics permits needed, which may include:
– Building permit – For general construction and structural work
– Electrical permit – For any new wiring, lights or circuits
– Mechanical permit – If HVAC systems are added
– Plumbing permit – If bathrooms or kitchen areas are added
The conversion design plans must meet the local residential building code for standards like:
– Fire separation between house and garage
– Structural integrity of foundations, walls and roof
– Lumber sizes and spans
– Electrical systems and circuits
– Insulation and energy efficiency
– Stair railings and headroom
– Ventilation and moisture control
An experienced contractor will be very familiar with permits and codes to ensure your garage attic meets requirements. Some municipalities may require drawings stamped by a structural engineer, so check with your local permit office.
Design and Layout Considerations
Here are some important garage attic design factors to optimize function and livability:
Ceiling height
Aim for at least 7 feet of headroom in the converted attic space, with 8 feet or higher ideal if possible. The roof pitch and truss design will determine maximum height.
Truss spacing
Standard roof truss spacing is 24 inches on center. Wider spaced trusses at 32-48 inches can allow for more livable attic space, albeit at greater cost.
Dormers
Adding shed or gable dormers to the garage roof provides more light, ventilation and usable living space. But dormers add cost and structural complexity.
Access stairs
The stairway width and landing size must meet minimum code requirements. Prefab spiral stairs or ladders help maximize floor area.
Garage door clearance
If still using the garage for parking, ensure enough clearance height for vehicles under new framing or stairs.
Insulation
Heavily insulate attic walls and floor for comfort and energy efficiency. Blown-in, batt and spray foam insulation are common options.
Ventilation
Attic ventilation is critical to prevent moisture buildup and excess heat. Gable vents, dormers, roof and soffit vents can maintain air flow.
Finishes
Unfinished space with exposed framing can be used for basic storage. For improved aesthetics, add drywall, tape/mud and paint. Consider pull-down attic stairs or ladders to conserve floor space.
Garage Attic Storage Ideas
An unused garage attic space is ideal for adding storage capacity. Here are handy storage solutions to consider:
– Shelving – Sturdy shelving units offer versatile storage for boxes, bins and household items.
– Racks – Vertical racks are great for stashing long items like ladders, lumber, sports gear and more.
– Cabinets – Base cabinets or wall cabinets provide enclosed storage for tools, supplies and valuables.
– Chests/Trunks – Weatherproof storage chests are useful for protecting seasonal items or holiday decorations.
– Pegboards – Pegboards allow customized tool organization for easy access and visibility.
– Loft – Framing a partial loft area can double your storage capacity.
– Lighting – Add ample lighting fixtures so you can see everything. LED shop lights work well.
– Flooring – Plywood or laminate flooring creates a clean surface rather than exposed joists.
– Ladder – Use an attic ladder rated for the required weight capacity and retractable for space savings.
– Insulation – Don’t forget to insulate walls, ceiling and garage door. Uninsulated spaces attract moisture.
Proper storage organization is important in an attic space. Use clear bins and labels to easily identify contents. Frequently accessed items should go nearest the access ladder or stairs. Make sure to leave walkways for accessing items deeper in the attic.
Garage Attic Living Space Uses
Beyond just storage, a garage attic can also be transformed into a versatile living or recreational space when properly finished. Some great ways to utilize the space:
Home office
An attic office gets work done in quiet and privacy. Just add insulation, walls, electrical lighting and outlets.
Artist studio
Painters, crafters and creatives will appreciate the abundant natural light from skylights and windows. Install washbasins and storage for supplies.
Home gym
With open space and headroom for equipment, a gym is a logical use for an attic over a garage. Ensure the structure can support heavy free weights.
Game room
What kid wouldn’t love an attic game room or hangout space? Decorate with fun themes and add gaming consoles or a pool table.
Guest suite
Finish the space thoroughly with insulation, drywall, flooring and a bathroom to create a private in-law suite or guest apartment.
Workshop
Avid DIYers will get ample use from a well-equipped workshop for tinkering and repairs. Include secure storage for tools, materials and projects in progress.
Teen hangout
Let teenagers claim the attic as their own cool haven for relaxing and spending time with friends. Add a TV, stereo and funky furniture.
Just about any live, work or play purpose can be fulfilled in a converted garage attic with the right layout and finishes. Let your imagination and needs guide the possibilities.
Key Takeaways
– Adding an attic over an existing garage can yield valuable extra living or storage space if the structure can support it.
– Careful planning is needed to meet building codes and structural requirements when framing a garage attic.
– Garage attic conversions can range from budget DIY builds to $100+ per square foot for higher-end professional projects.
– Finishing the attic space allows for flexible multipurpose uses beyond just storage like a home office, guest suite or hobby room.
– With proper permits and experienced contractors, converting a garage attic is a worthwhile way to expand and customize your home.