Can you build a screened-in porch on existing deck?

Quick Answers

It is often possible to convert an existing deck into a screened-in porch by adding screening and other structural elements. However, there are important factors to consider such as meeting building codes, load capacity of the existing deck, and integrating the new screened structure into the home. Proper planning and permissions are essential.

Is it Allowed by Building Codes?

The first step is to check with your local building department to see if converting your deck to a screened porch is allowed. There may be zoning restrictions or building codes that regulate adding enclosed porches. Requirements vary by location but often include:

• Obtaining a building permit
• Meeting setback requirements from property lines
• Following design load requirements if adding a roof
• Using proper materials like screened panels and framing
• Meeting electrical wiring and outlet requirements
• Adding adequate ventilation and emergency egress

The building department can help guide you through the specific regulations in your area. Failing to get proper permits can risk fines or even removal of the illegally built structure.

Assessing the Existing Deck

The current deck must be evaluated to determine if it can support adding the weight of screened walls, a roof, and other additions required to enclose the space. Several factors are important:

• Age and condition of the deck – older or poorly maintained decks may need repairs first.
• Type of framing used – the size and spacing of joists impacts weight capacity.
• Load capacity of ledger board attachment to the house.
• Soil conditions and type of foundation supporting deck footings.

In some cases, additional support beams, footings, or other reinforcements may be needed to support the added load. A building contractor can assess the existing structure and determine what upgrades are required.

Deck Framing Types and Load Capacity

*psf = pounds per square foot

Decks built with thicker, closer spaced joists can support more weight. Consult a building contractor to verify capacity.

Design Considerations

If building codes allow enclosing your deck, there are many design decisions to make such as:

• Partial or Full Enclosure: Screens can be added to just the sides or also include screen panels with framing above to create a roof.
• Access: Doors and windows can connect the porch to indoor spaces. Screened panels may have movable sections or openings.
• Foundation: The existing deck footings may be sufficient or need adjustments depending on the porch design.
• Framing: Supplemental posts, beams, and joists may be needed to add structural support.
• Roof: Trusses or rafters can create a gabled or shed style roof. The roofing material needs to be weather resistant.

Work with an experienced deck contractor to evaluate options and develop the right plans for your unique home setup.

Building the Enclosure

Once proper planning and permits are in place, construction can begin. The process typically involves:

1. Strengthening the existing deck framing with additional posts, footings, and structural members as needed.
2. Attaching vertical 4×4 wood posts around the exterior to frame the walls. These are often spaced 4 to 6 feet apart.
3. Adding header beams across the top of the posts and band boards at floor level to complete the wall framing.
4. Attaching angled knee braces for lateral strength and rigidity.
5. Covering the walls with screening material such as fiberglass, pet-resistant screen, or fine stainless steel mesh on all sides.
6. Adding exterior trim boards around the framed screen panels.
7. Installing a framed roof structure if designed and sheathing it with weatherproof materials such as asphalt shingles.
8. Finishing with flashing, fascia, ceilings, lighting, and electical as desired.

Proper moisture barriers, ventilation, and footings are critical. Foundation alterations may be needed to allow adequate structural support while meeting frost line depth requirements in your area.

Typical Porch Section Drawing

      Shingles
       |
  Rafters
   |
Ceiling
   |
 Screen 
  Walls
   |
 Floor 
  Joists
   |  
 Footings

What are the Costs?

Converting an existing deck to a screened porch is a significant project that requires professional expertise. Here are some typical costs:

• Building permits – $100 to $500
• Structural reinforcement of existing deck – $500 to $2,000
• New porch framing materials – $15 to $25 per sq.ft.
• Screen panels and trim – $3 to $8 per sq.ft
• Roofing – $5 to $10 per sq.ft.
• Electrical and lighting – $2,000 to $4,000
• Ceiling and finishes – $2,000 to $4,000
• Labor costs – $50 to $100 per hour

Total costs for a 10×12 foot screened porch built on an existing deck often range from $10,000 to $20,000 or more depending on the specifics. Get quotes from qualified deck builders to estimate your particular project.

Alternatives to Consider

Screening in an existing deck has challenges. Some alternate options to achieve expanded living space include:

• Add a freestanding screened gazebo or pergola next to the deck for an outdoor room.
• Replace the deck with a new porch designed for screened enclosure from the start.
• Build a 3-season sunroom addition with insulated walls and windows instead of screens.
• Install window screens and awning panels on the deck for partial protection.

A purpose-built screened porch or sunroom addition may allow more design flexibility, better insulation, and integration with the home’s wiring and utilities.

Conclusion

Converting a deck to a screened-in porch takes careful planning but can greatly enhance your enjoyment of the space. Check local building codes, assess the existing deck structure, and work with an experienced contractor on the project. A well-built screened porch provides an excellent outdoor living area protected from insects and weather. With proper upfront planning, you can successfully build an attractive and functional screened porch onto many existing decks.