This step by step woodworking project is about how to build a lean to addition. If you need to attach a simple lean to roof to a shed or on already existing building, I’ve got you covered with step by step plans. This structure is heavy duty and it features a roof with a 11.5 degree slope, but please follow the building codes and hire a professional contractor if you don’t have the right skills to undertake the project on your own.
We recommend you to invest in the best materials you could afford. Therefore, you should buy weather-resistant lumber, such as pressure-treated lumber, cedar or redwood. If you use regular pine, I recommend you to apply the appropriate products to enhance its durability. Always take accurate measurements before adjusting the size of the components at the proper size. Drill pilot holes trough the components before inserting the wood screws, to prevent the wood from splitting. See all my Premium Plans HERE.
Made from this plan
How to Build a Lean to Addition
Materials
- A – 3 pieces of 4×4 lumber – 84″ long POSTS
- B – 2 pieces of 4×6 lumber – 160″ long TOP BEAMS
- C – 4 pieces of 4×4 lumber – 36″ long BRACES
- D – 1 piece of 2×6 lumber – 160″ long LEDGER BOARDS
- E – 12 pieces of 2×6 lumber – 110″ long RAFTERS
- F – 1 piece of 1/2″ plywood – 4’x88″ long, 1 piece – 4’x72″ long, 1 piece – 40″x48″ long, 1 piece – 48″x24″ long, 48″x96″ long, 1 piece – 15 3/4″x88″ long, 1 piece – 15 3/4″x72″ long ROOF
- G – 2 pieces of 1×8 lumber – 111 3/4″ long, 1 piece – 161 1/2″ long TRIMS
- H – 150 sq ft of tar paper, 150 sq ft of asphalt shingles ROOFING
- 3 pieces of 4×4 lumber – 8 ft
- 1 piece of 4×6 lumber – 14 ft
- 1 piece of 4×4 lumber – 12 ft
- 1 piece of 2×6 lumber – 14 ft
- 12 pieces of 2×6 lumber – 10 ft
- 5 pieces of 1/2″ plywood – 4’x8′
- 150 sq ft of tar paper, 150 sq ft of asphalt shingles
- 2 pieces of 1×8 lumber – 10 ft
- 1 piece of 1×8 lumber – 14 ft
- 1 5/8″ screws
- 5″ lag screws
- concrete form tube
- 3 post anchors
- 20 pieces of 5″ screws
- post to beam connector
- rafter ties
- rafter hangers
- Screws for Strong ties
- wood glue, stain/paint
Tools
- Safety gloves, glasses
- Miter saw, jigsaw
- Chalk line, tape measure, spirit level, carpentry pencil
- Drill machinery and drill bits
Time
- One Week
Building a lean to addition onto shed
The first step of the project is to layout the attached lean to cover posts. Therefore, select the location and level the surface with attention. Make sure you remove the vegetation layer and even out the surface. Use batter boards and string to layout the location of the posts. Apply the 3′-4′-5′ rule to each corners, so you make sure they are square. Measure the diagonals and make adjustments so they are equal.
You should know this lean to roof plan is just an example, so you can understand the techniques required for the job. However, you can adjust the size of the structure to suit your needs. You can change the height of the posts, the angle of the roof and size of the footprint.
After marking the location of the posts, you need to dig 3′ deep holes in the ground, using a post hole digger. Install tube forms and fit the posts into place, making sure they are perfectly plumb. Fill the forms with concrete and install the anchors. Use string and batter boards to align the anchors.
Please read the local codes so you determine the RIGHT depth for the footings. In addition, in some areas you might need to set the posts to concrete. That is why it’s essential to read the local codes, because the front line depth differs according to your location.
Use chalk line to make the top of the posts, so they are perfectly level one with another. Use a circular saw to cut the top of the posts. Leave the braces on, until you build the frame for the lean to roof.
Fit the beams to the top of the posts and plumb them vertically. Use post to beam connectors to lock them together tightly. Leave equal overhangs on the front and back of the top beam. If you cut the top of the posts level, the beam should be perfectly horizontal.
Use 4×4 lumber for the braces. Use a miter saw to make 45 degree cuts to both ends of the braces. Check if the posts are plumb and if the top beams are perfectly horizontal before attaching the braces. Drill pilot holes and insert 5″ screws to lock the braces to the frame.
Next, attach the 2×6 ledger boards to house. The ledger is placed to the house considering a roof slope of 11.5 degrees. If you want to change that, just place the ledger higher or lower. It is important to read the local codes before attaching the ledger boards. In this example I consider it’s ok to use 5″ lag bolts, but that doesn’t probably apply to your codes. The codes also shows the number of bolts needed and the distance between them.
Next, we will build the rafters for the patio cover using 2x6s. As you can see in the diagram, use a miter saw to make a 11.5 degree cut to one end of the rafters.
Fit the rafters to the top of the patio cover structure. Use the info from the diagram to space the rafters every 16″ on center. The number you see in the plans represents the distance between the rafters. Use rafter hangers to secure the rafters to the ledger boards. Use rafter ties to secure the rafters to the support beam. I recommend you to use 1 1/2″ structural screws to secure the ties into place.
Use 1/2″ plywood for the roof sheets. Make cuts to the sheets and lay them on top of the roof structure. Leave no gaps between the sheets and align everything with attention. Drill pilot holes and insert 1 5/8″ screws, every 8″ along the framing.
Use 1×8 lumber for the side roof. Make angle cuts to the trims with a miter saw. Fit the trims to the sides of the lean to roof and lock them into place with 6d nails.
Fit a trim to the front of the lean to roof.
Notice that you need to add flashing between the wall of the house and the roof of the lean to roof. In addition, caulk the joints so you prevent water infiltration.
You could fit asphalt shingles to protect the roof, as it is a straight forward solution. Therefore, install roofing felt over the roofing sheets, making sure the strips overlap at least 2″. Secure the tar paper to the plywood sheets with roofing staples. Place a starting course at the bottom of the roof, before installing the asphalt shingles. Always read the manufacturing instructions before starting the installation, as there are several aspects that differ.
The first course should star with a 3 tab shingle, the second course with a 2 1/2 tab , the third course with a 2 tab, the forth course with a 1 1/2 tab, the fifth course with a 1 tab, the sixth course with a 1/2 tab. Repeat the process from the beginning, starting with the seventh course. Don’t forget that the shingles should overhang from the drip edge about a 1/4″. In addition, secure the asphalt shingles to the roof decking with tacks.
You’ve got to like the simplicity of the patio cover. It is super easy to build and you will love the shade during the hot summer days, especially if you have an ATV or a bike to park under. This would also make for a cute porch.
This patio cover is built on a sturdy 4×4 structure. You can adjust the slope of the roof to suit your needs.
Last but not least, you need to take care of the finishing touches. Therefore, fill the holes with wood putty and then smooth the surface with sandpaper. Apply a few coats of paint or stain over the components to enhance the look of the shed and to protect the components from decay. You should also check my free plans on how to build a patio cover. I also have lots of other free pergola plans on the site, so make sure you check them, as well.
If you want to download the plans. just click on the GET PDF PLANS button bellow.
Smart Tip: Apply a few coats of stain or exterior paint to the components, in order to protect them from decay and water damage. Make sure you choose quality components that suit your needs and tastes. I am pretty sure this covered patio will be the favorite spot in your garden, so give it a chance. Nothing compares to a coffee or a hot tea in nature.
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