How to Build a Porch on a Cabin

The best seat in the house

Building a porch onto your cabin adds more than just value to the recreational property. An outdoor area to gather with family and friends extends the cabin's living space and helps set the mood for rest and relaxation. Besides entertaining, a porch can also provide storage for outdoor items, such as recreational equipment, firewood and footwear. With many designs to choose from, a porch enhances the overall look of any cabin, while adding a functional architectural element as well.

Things You'll Need

• Mason's line
• Measuring tape
• Wooden stakes
• 3-inch nails
• Quick drying concrete
• Gravel
• 5-gallon bucket
• 12-by-12-by-7 precast concrete piers with attached post base hardware
• Shovel
• 4-by-4 pressure treated posts
• 4-by-6 beams
• Hurricane ties
• Hammer
• Saw
• 2-by-6 lumber
• Z-flashing
• 3.5-inch lag screws with washers
• Joist hangers
• 3-inch deck screws
• Angle brackets
• Drill
• 3/16 drill bit
• 3.5 inch deck screws
• Socket wrench

Instructions

Porch Design and Preparation

1. Check with the local building department for necessary permits, codes or restrictions. Measure the area where you want to place your cabin porch. Mark each of the corners with a wooden stake, tying mason's line between them to mark the perimeter.

2. Tie two additional lines diagonally crossing each other to form four triangles. Measure the opposite triangles to determine if the porch perimeter is square. Adjust the positioning of the stakes where necessary.

3. Measure the length of the porch. Subtract 3 inches, and cut one 2-by-6 board to that length. Measure 3 inches below the door and temporarily nail the 2-by-6 ledger board lengthwise to the cabin with 3-inch nails.

4. Measure and cut one piece of Z-flashing the same length as the ledger board. Slide the flashing behind the board with the small lip facing downward. Remove the temporary nails, and fasten the board to the cabin using 3.5-inch lag screws with washers.

5. Calculate the number of 4-by-4 supports necessary for the porch. This will vary depending on your porch size. Typically, you will need one support for every 12 square feet, using 4-by-6 beam construction. Consult a beam span chart to determine specific placement, and mark the location of each footing needed for supports.

6. Dig 1.5-foot wide holes deep enough for the footings, generally this will be below the frost line in your area. These will be spaced along the porch perimeter and in center, based on calculations in step 5.

7. Add a thin layer of gravel to the bottom of each hole. Mix concrete in 5-gallon bucket, and fill each hole. Soak precast concrete piers in water, then push each into concrete about 1 inch.

Framing and Construction

1. Attach mason's line to the underside of the ledger board. Extend it out over the first pier keeping it level and perpendicular to the ledger board. Measure the distance from the concrete top of pier to the string and subtract 5.5 inches. Measure and cut 4-by-4 pressure treated posts to that length.

2. Repeat the measuring process for each post. Measure and cut 4-by-4 pressure treated posts accordingly. Secure posts to piers vertically using nails.

3. Measure the porch lengthwise, and cut 4-by-6 joist support beams accordingly. The number of beams needed will be determined by the span chart in step 5 above.

4. Attach each beam lengthwise to a 4-by-4 post using post cap flanges and nails. Measure the porch width, and cut two 2-by-6 rim joists to be attached to the outside edges of the ledger board based on the porch width. Secure these to ledger board with 3-inch deck screws.

5. Cut one 2-by-6 header joist the same length as in step 3, and secure it to rim joists using 3-inch deck screws. Reinforce inside corners with angle brackets and nails. Attach joist hangers to 2-by-6 ledger and header joists every 16 inches on center using nails, then secure joists to support beams using hurricane ties and nails.

6. Calculate the number of 2-by-6 decking planks needed, allowing a 1/8-inch gap between boards. Measure the porch frame lengthwise, and cut planks accordingly. Secure planks to floor joists using 3.5-inch deck screws.

7. Install prefabricated railings and stairs to manufacturer's specifications. Consult a contractor to construct roofing, if desired.

Tips & Warnings

• Paint or shellac the completed cabin porch with an outdoor approved product. Use manufacturer's suggested nails for hardware connectors. Drill pilot holes before attaching lumber with wood screws. Smaller porches placed close to the ground may not need beam construction. Consult your local building department regarding this.

• Always consult a beam span chart to determine lumber size and species, as well as beam and joist spacing. (See Resources.) Wear a dust mask and goggles when sawing lumber.

References

• "Decks 1-2-3"; Meredith Publishing Group; 2006

Resources

• Decks.com: Porch Anatomy
• Southern Pine by Design: Guide to Porch Flooring and Construction
• Ace Hardware: Building Your Deck
• California Outdoor Living Decks: Decking Beam Sizes