The complete guide
How to Choose the Right Cover for an L-Shaped Outdoor Sectional
The problem with leaving a sectional uncovered
Outdoor furniture is sold on the promise that it lives outside. In practice, most of it is only half built for that. Frames are usually fine. Cushions, cord trim, resin weave and powder coating are the parts that give up first, and they give up slowly enough that you do not notice until you compare the sofa to a photo from two summers ago.
Three things do the damage. Ultraviolet light breaks down the dyes and fibers in cushion fabric, which is why the side facing the afternoon sun always fades first. Water soaks into foam and seat cushions and never quite dries out, which leads to that musty smell and eventually to mold spots along the seams. Then there is everything else that falls out of the sky, including pollen, leaf tannins, dust, tree sap and bird droppings, all of which stain and all of which grind into the fabric every time someone sits down.
A cover deals with all three at once. It is the cheapest thing you can do to make an expensive lounge last.
Why L-shaped sets need a shaped cover
A rectangular tarp over an L-shaped sofa leaves you with a lot of loose fabric at one end and a gap at the other. Loose fabric is not harmless. It catches wind like a sail, it collects pools of rainwater that sag and eventually drip through, and it rubs against the frame until the coating wears.
A shaped cover follows the footprint. The long panel runs the length of the sofa back, the short panel turns the corner and runs down the return, and the whole thing sits close enough to the furniture that water runs off instead of sitting still. That is the whole case for buying a cover that matches your layout rather than a generic one.
Right facing versus left facing
This trips up more people than anything else, so here is the simple test. Stand in front of your sofa, looking at the seats the way you would if you were about to sit down. If the shorter section, the chaise or corner return, runs away to your right, your sectional is right facing. If it runs to your left, it is left facing. A right facing cover will not fit a left facing sofa, because the shaped panels land on the wrong sides.
Some retailers describe orientation from behind the sofa, which is where the confusion comes from. Stick with the from-the-front rule and you will get it right.
Getting the measurements right
This cover is made for right facing L-shaped sets up to 110 inches wide along the back length, up to 85 inches along the right side, and up to 32 inches deep. Those are maximums, not targets.
Measure your own lounge with a tape, not by eye. Take the back length wall to wall at the widest point, including arms. Take the right side the same way, from the back corner out to the end of the return. Then take the depth from the front edge of the seat cushions to the back of the frame, and check the height from the ground to the top of the back cushions.
A little slack is fine and makes the cover easier to pull on. A lot of slack is a problem. Excess fabric billows, pools water and wears faster. If your sofa measures well under the maximums, it is worth seeing whether a smaller size in the range suits you better. That is the honest difference between the best right facing sectional cover for your patio and one that just happens to go over the top of it.
What the fabric actually does
The shell here is 600D polyester canvas with a waterproof backing. The "600D" figure refers to denier, a measure of yarn thickness. Higher numbers mean heavier, denser yarn and a tougher fabric. At 600D you are in solid all-weather territory, heavy enough to resist tearing on a windy night and to take hail without punching through, but still flexible enough to fold and handle.
The waterproof backing is a separate layer bonded underneath. Polyester on its own is water resistant at best. The backing is what turns it into a barrier that holds off sustained rain.
The cover is also described as UV resistant, which matters as much as the waterproofing in a sunny climate. UV is what makes untreated covers go chalky and brittle after a season or two, at which point they start cracking at the folds.
Vents and straps, the unglamorous parts
Two features do most of the real work and neither looks impressive in a photo.
The structured air vents on the sides let air pass through. Without them, a sealed cover does two bad things. It inflates in wind, straining the seams and often lifting right off, and it traps warm humid air against your cushions where moisture condenses overnight. Vents break that cycle. Any vented outdoor furniture cover will outlast a sealed one in a damp climate.
The click-close clip buckle straps go underneath and fasten around the sofa legs. Elastic hems alone are not enough on a large lounge. Clipping the straps snug pulls the cover tight to the frame so it does not flap, and flapping is what destroys covers. Every gust that lifts and drops the fabric works at the stitching a little more.
Fitting it the first time
Give yourself ten minutes and do it in daylight. Clear anything off the sofa first, including side tables and cushions you want kept dry separately. Drape the cover over the back of the lounge, find the corner seam and line it up with the inside corner of the L, then unroll the short panel along the right side.
Pull the front down last, walk around the whole thing to even out the drape, and clip the straps underneath. Tighten them until the cover sits close but not stretched. If the fabric is drum tight across the top, that is too much, and the seams will carry that load every time the wind pushes on it.
If water pools on the top after rain, add a cushion or an upturned bucket under the center to create a slope. It is a crude trick and it works.
Care and storage
Cleaning is simple. Brush or shake off leaves and loose dirt before you remove the cover so the debris does not tip onto your cushions. For marks, use a damp cloth with mild soapy water, then rinse with a hose. Let it dry completely in the air before folding.
Keep it out of the washing machine and the dryer. Both will damage the waterproof backing, and once that layer delaminates the cover is just a heavy sheet. Skip bleach and solvents for the same reason.
If you pack it away over summer, dry it thoroughly first, fold it loosely, and store it somewhere cool and sheltered. Damp fabric in a sealed container grows mold within weeks.
Who this suits
This cover makes sense if you have a right facing L-shaped outdoor lounge that stays on a deck, patio or lawn year round and you have nowhere to move it. It is also worth having if your sofa sits under a tree, since sap and leaf stain are harder to remove than plain rain.
It is less relevant if your furniture lives under a solid roof with walls on two sides, or if you store it in a shed every autumn. In those cases a lighter dust cover does the job.
The short version
Work out whether your sectional is right or left facing by standing in front of it. Measure the back length, the right side and the depth, and compare those against the 110 by 85 by 32 inch maximums. Pick the closest fit rather than the biggest option. When it arrives, clip the straps properly and check the drape so water runs off rather than pooling.
Do that and a heavy duty 600D polyester cover will quietly save you the cost of replacing cushions, which is where the money really goes on outdoor furniture.