I built this outdoor couch as a Mother's Day gift and it really turned out better than I imagined. I'm 6'5" and my family is all tall and so it's hard to find a comfortable outdoor chair or bench that isn't low to the ground so I decide to make my own. Now if you want it shorter just cut off an inch or two off the legs and it'll be perfect for you. My original plan was to use some rustic looking wood I had laying around but my mother doesn't like the rustic look but I'm including some pictures because they look awesome, she just likes the clean look so that's what I did.
Step 1: Cushions
The first thing I needed to find was cushions then I could design the frame off the cushion size. Target was by far the cheapest for the size and color choices I wanted which for the seat cushion is 24" by 22" by 6" thick for $26. The back was 20" by 18" by 3" for $15.
Step 2: Design
If you wanted a 4 or 2 cushion length couch this is where you can make that change, customizing it however you want it but use the cushion sizes to design it. The most important thing about this couch is not the size but the 5 degree slope and 15 degree back angle, that's what makes it really comfortable. Now that I had the cushion sizes I could design the frame. So I decided to use Sketchup, which I've never used before but I will now for any future project. It really helped visualize problems before I even purchased the materials. The key to a comfortable couch or chair is angles. The seat part was around 5 degree slope and the back around 15 degrees. If you ever sat in a perfectly flat bench or chair you'll know exactly what I mean, you need to put some angles to make it really comfortable.
Step 3: Gathering Materials
Once you have the design done you can calculate the right amount of materials so you don't waste money buying too much or not enough and have to make trips. For me I had leftover material that I cut to the size I wanted but if you had no lumber and your using my exact design here's a lumber dimension list.
1= 10 foot 4" by 4" for the legs around $12 or up depending on wood type
8= 8 foot 1" by 4" for the seat and back strip pieces $2 for furring strips
5= 8 foot 2" by 4" for the main frame around $2.50 each for basic stud
1= 66" 2" by 6" for the arms $5 and up depending on wood type
1= 8 foot 2" by 2" for back slats to attach to around $2
Screws = 2 1/2" and 1 1/4" outdoor screws around $10 = for each box
1 gallon of Primer $20
1 gallon of Paint $24
Step 4: Construction
Predrill holes to prevent splitting wood especially on the 1" by 4" slats.
I cut the 10 foot (4" by 4") at 28" for each leg. If you want a shorter overall couch this is where you trim off another inch or two, so 27" or 26". Then cut 2 of the (2" by 4") at 82". Using 2 1/2" screws, attach one of the 82", (2" by 4") to the front of the post 16 1/2" up from the bottom of the leg, that's the front of the couch. Now attach the 2nd (2" by 4") to the other 2 posts, (4" by 4") at 14" up from the bottom of the leg. That should give you about 5 degree angle. Take another (2" by 4") and cut 2, 30" pieces with a 5 degree angle cut on each end, make sure that it is cut correctly on both sides so you have that 5 degree slope. Screw those pieces together to make your main frame.
Now the arms. I cut the (2" by 6"), 5 1/2" on one end and 3 1/2" on the other to give it a flare out but you can leave it a solid (2" by 6") if you want. Cut a (2" by 4"), 72" for the extra support for the seat. I placed it 16" in from the front of the couch.
Now place the back rail. Take a (2" by 4"), and cut it to 82" and I put a
15 degree rip cut. You could use a table saw but i just clamped it down and used a circular saw with a guide.
Next up was the (1" by 4"), strips. The back slats were 24" and the seat slats were 33". On the 24" slats I cut a 10 degree angle on one end (15 degree - 5 degree=10 degree) so they would fit flush against the seat slats. I had 12 that I spaced evenly. I used a method that is used for the spindle spacing for a railing or you could just eye ball it because the cushions will cover them up. Roughly 3" spacing, just make sure that the back strips and seat strips line up and it will look good even if the spacing isn't exact. I attached the strips of (1" by 4"), with the 1 1/4" screws just make sure you predrill the holes to avoid splitting the wood. Attach the seat slats first then the back slats. Attaching the slats for the back I layed the slats against the back rail 15 degree rip cut to get the angle but I also used my phone and a level app to check the 15 degrees. I cut the (2" by 2"), board so it was the same length as the farthest slats at 72". I layed it on top of the seat slats and attached it from underneath with the 1 1/4" screws.
Step 5: Painting or Staining
Now I needed to protect it from the weather. I decided to paint it white to continue that clean look but as you can see from the other pictures if I used the rustic looking wood I would've stained it. If you use pressure treated wood I would let it dry out for a month or two and then stain it or paint it using a good quality stain or paint and at least 2 coats. As for the paint the key I learned to any good quality outdoor paint job is primer. Primer is a must for a longer lasting outdoor paint job. I used Zinsser 123 primer and Glidden exterior paint. I used a paint sprayer which made it easier to get into all the nooks and crannies. 1 gallon of Primer and Paint is more than you need but I will end up using it for other projects so you could buy less for just this project.