DIY Outdoor Shed Addition

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To build an addition on your outdoor storage shed or workshop:

1. Floor Framing: Assemble the floor framing from pressure treated 2×6 lumber.
2. Foundation: Set the floor framing on a concrete block foundation and attach to the shed wall with lag bolts.
3. Flooring: Nail or screw a treated plywood to the joists.
4. Wall Framing: Construct the walls for the addition from 2×4 lumber.
5. Rafters: Cut and nail 2×4 rafters to a ledger board, then attach the ledger board to the wall of the shed.
6. Roof Sheathing: Attach plywood plywood sheathing to the rafters.
7. Siding: Install sheet siding on the shed addition walls.
8. Roofing: Roof the shed addition with asphalt shingles or roll roofing.
9. Roof Flashing: Slide metal flashing under the shed roof and on top of the addition roof and nail in place.
10. Eaves: Add trim boards to the eaves of the shed addition.
11. Door: Construct a door from plywood reinforced with a 1×4 frame.
12. Ramp: Build a ramp to allow easy access to the shed.

Watch this video to find out more.

Further Information

• Considerations When Building a Storage Shed (video)
• Innovative Storage Shed Designs (video)
• Designing and Building a Storage Shed (article)
• How to Assemble a Storage Shed (video)

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Scott Gardner: I came up with this idea to build an addition basically to the shed.

Joe Truini: Oh, that’s nice.

Scott Gardner: So we kind of refer to this as the lawn and garden shed attached to the workshop.

Joe Truini: All right, that’s great.

Danny Lipford: Because the original structure was built on a treated two by six floor system, Scott and his sons built the floor for their addition from the same material. Since it was only four feet by ten feet, they built it on the ground before attaching it to the existing shed with long lag bolts.

After they attached the treated plywood decking to the floor, Scott laid out and built the walls for the addition before he set them in place. Then they leveled and secured them to the floor and to the shed walls. All the rafters were also attached to a ledger board before they went up over the addition. The new roof matched the slope of the shed roof but it tied in slightly lower on the wall to simplify the building process. Flashing was added along that wall to keep the water out.

Next, the sheet siding for the addition was nailed directly to the studs to quickly enclose the space. So after some shingles and a few trim boards were added the structure was complete. To create the odd sized door Scott used some plywood with one by fours attached to the face to add extra strength and match the existing shed doors. The final touch was a ramp to allow easy access to the inside of the addition.

Joe Truini: It’s only about four feet wide, but you can see it’s plenty of space here for a power washer and a lawn mower. I love that elevated shelf. That would be dead space otherwise, way back there.

Scott Gardner: Well, and there’s just tons of little small stuff that you use around the lawn and garden all the time. And so, the great thing is it’s out of the weather.

Joe Truini: Right.

Scott Gardner: It’s safe. You can lock it up.

Joe Truini: Love that idea you put in. I like the idea that you put vents there to keep that area a little cooler.

Scott Gardner: Exactly. Well, when you store gasoline in there and that kind of thing, you don’t want all that stuff to, all those vapors to accumulate in there.