How to Build a Garden Shed Addition (page 2 of 2)

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Planning and Design

You'll Have to Get a Building Permit
Call your local building inspections department to find out if your shed location is OK and what's required to get a building permit. Most cities will accept a plan drawn to scale on 1/4-in. graph paper if it includes all the structural details.

Every region has a few unique building requirements. In cold Northern climates like ours, deep footings are required to prevent frost heaving. In areas with high winds or earthquakes, you'll need special metal framing anchors to tie everything together. Ask your building inspector what's required in your area.

Use the Best Cedar 4x4s You Can Find
Most of the materials for this shed are available at home centers and lumberyards. We spent $2,200 for lumber, windows, doors and roofing, and $400 more for the pea gravel base and concrete pavers. Here are a few pointers for your shopping trip:

Pick straight, dry cedar 4x4s. Bowed or twisted lumber will cause trouble when it comes time to install the windows and door. Check at both lumberyards and home centers.
Make sure the 6x6s are .60 treated, not the less durable .40 that’s sometimes used for landscaping timbers. You'll probably have to order them.
Barn sashes are sold at some home centers and farm-supply retailers. If you need help finding them in your area, call Lindsay Windows at (507) 625-4278. If you're willing to modify the plan dimensions, consider using old storm windows in place of the barn sashes. Contractors specializing in window replacements often throw these away.
Search for an interesting old entry door at salvage yards or architectural antiques dealers, or buy a new one like ours for about $150.

Begin With a Square and Level Foundation
To quickly double-check the dimensions on your plan, mark the post locations on the 2x4 bottom plates and cut the plates to length. Use the dimensions from these plates to set up the batter boards and strings. 'best to align the strings with what will be the outside edge of the 6x6 foundation beam. (Remember to deduct 1 in. from the total length of the front wall and 1/2 in. from each side wall so the walls will overhang the beams by 1/2 in.. We aligned our strings with the inside edge of the 6x6 because the concrete patio was in the way of setting up batter boards. Take your time getting these strings perfectly level and square.

Piers and Beams Make a Strong, Simple Foundation
Our shed is held up by 6x6 treated beams bolted to 42-in. deep concrete piers, which are appropriate for the frost depth in our area. Your building inspector will tell you how deep to go in your region. We rested the end of the 6x6s on notches cut into the garage foundation. If you can’t do this, add piers at these locations. About a week before you plan to dig, call the utility companies to locate buried wires or pipes. Use 8-in. dia. cardboard forming tubes for the piers. They allow you to easily establish accurate pier height. Figure one 60-lb. bag of concrete mix for every 1-ft. length of 8-in. dia. tube. After pouring the concrete, position the anchor bolts 2-3/4 in. from the string so they’ll end up in the center of the 6x6 beam.

TIP: Before the concrete hardens, double-check that all the footings are level with each other using a long, straight board with a 4-ft. level on top.

Then let the concrete harden overnight. Before you start on the 6x6 beams, dig out enough soil to allow space for 3 in. of gravel under the beams and 5 in. under the concrete patio block floor for good drainage.

Next, you'll cut the 6x6 beams to length and bolt them down. Mark the beam locations on the footings and cut the 6x6s to align with these marks. Remember to add the amount that will rest on the garage foundation onto the shorter end beams. Paint wood preservative onto the cut ends of the beams before you bolt them down, and countersink the nuts and washers so the walls will slide on easily.

Skip the Complex Rafter Calculations
Mock up a wall and rafter to make exact patterns rather than using math. After you've marked where the rafter crosses the 4x4 top plate, subtract 5 in. (1-1/2 in. for the 2x4 bottom plate and 3-1/2 in. for the 4x4 top plate) from the high side to arrive at the length of the 4x4 wall posts. Cut all the posts off square at this length. Then assemble the walls and brace them plumb and square. To tie the side walls to the house, we cut out a slot in the siding and slid the 4x4 wall post against the sheathing. Then, since there were no studs in the existing wall at these locations, we added some from inside the garage to provide solid wood for attaching the walls. After nailing the walls in place, use a handsaw to cut out the bottom plates that run across the door openings.

Shopping List

Cut out a rafter pattern and set it up on the walls to check the fit. This long rafter will need two “bird’s-mouth"cuts, one to fit over the 4x4 top plate of the long front wall and one for the short 4x4 beam that holds up the lattice-covered overhanging section. Adjust the fit as needed and use the pattern to mark the remaining long rafters. Make a second pattern for the shorter rafters.

Sight along the top of the front wall to make sure it's straight before you secure the rafters. Then nail down the roof plywood and install the soffit plywood and fascia boards. Match the soffit and fascia details to those on your house.

When you cover the roof with roofing paper, tuck the new paper under the existing shingles and paper. Plan the shingle installation and chalk the lines so the old and new shingles line up. Fasten the shingles with 1-in. galvanized roofing nails according to the instructions on the wrapper. When you get to the top, carefully lift the old shingles and remove the first row of roofing nails with a flat pry bar to allow the new shingles to slide underneath.

We Made the Exterior Simple but Attractive
Next, fill in the triangular sections above the wall on each end. Then close in the shed by filling the spaces between the posts. With our shed design, you don’t have to install door and window jambs, but you do have to cut angles on the 3/4-in. x 2-3/4 in. drip cap that fits below the siding, and on the 2x4 windowsill. Use a table saw for these cuts and to rip a 2x4 down to 2-5/8 in. for the pieces above the windows. We mounted Wright Products Corp. No. V405 storm window adjusters 10 in. above the sill to hold the sash open and lock them shut.

CAUTION: The glass in the barn sash next to the entry door must be replaced with safety glass. Take one barn sash to a glass shop or full-service hardware store and ask to have the glass replaced with tempered safety glass, Plexiglas or 1/4-in. laminated safety glass, or order the glass and replace it yourself.

Patio Pavers Make a Great Floor
We laid 18-in. square concrete patio pavers over a level bed of pea gravel. Cut the pavers along the walls and at the doors with a dry-cut diamond blade mounted in a circular saw. We also used the pavers to build a ramp into the yard from the sliding door.

Build a No-Sag Barn Door
Install the doors after the floor. Construct the sliding door by driving 1-1/4 in. galvanized or stainless steel screws through the backside of the 1x6 tongue-and-groove boards into a 1x4 cedar frame. Mount a 2x4 open bar holder bracket to the 6x6 to keep the bottom of the door from swinging out. We installed a barn door latch on the outside to secure the door.

Customize the Shed for Your Own Hobbies
To provide a separate planting area inside the shed, we built a wall of 2x6s spaced 30 in. apart and covered on the back with 1/2-in. plywood. Metal shelf standards and clips support 2x6 shelves for pots and planting supplies. We created a narrow, hollow space next to the windows to allow access to the window latch.

Use the lattice-walled overhang to store a gas grill or to hold a potting bench like ours. Or use it as a vine-covered sitting area. Cut the cedar lattice panels to fit between the 4x4s and secure them with 1x2s nailed on each side. Make the bench top by screwing a 2x4 ledge to the 4x4 posts and cutting 2x6 cedar boards to rest on top.

Protect Your Shed With Top-Quality Finishes
To retain the natural look of your cedar shed, apply two or three coats of a top-quality clear exterior finish. Paint the door and exterior trim with alkyd primer and two coats of top-quality exterior latex paint.