Key takeaways
- Zipper location: along the back edge, ideally wrapping around the sides by a few inches, makes inserting thick foam easier.
- Welting or piping: gives a crisp edge and reinforces seams on boxy cushions.
- Thread: UV-resistant polyester or PTFE-based thread outlasts standard thread, which can rot in the sun before the fabric does.
- Ties or non-slip bottoms: back cushions slide on deep seats; ties or a grippy base reduce that.
- Drain grommets or mesh bottom panels: help water escape from thick cushions.
Deep seat patio cushion covers fit only when you match three measurements to the half inch: width, depth and the boxed edge (gusset) height, which on deep seating is usually 5–6 inches for seat cushions and 4–6 inches for back cushions. Most fitting problems come from ordering the right width and depth but the wrong gusset, or from sizing to compressed old foam. This guide focuses on deep seating specifically and on refitting tired cushions; the same method works for ordinary patio furniture seat cushion covers, which are simply thinner, usually 2–4 inches.
Common Deep Seat Cushion Sizes
Deep seating, the lounge-style patio chairs and sofas with seats 24 inches deep or more, uses larger, thicker cushions than dining chairs. Typical sizes:
| Cushion | Typical width | Typical depth | Gusset/thickness |
|---|---|---|---|
| Deep seat chair, seat | 23–25 in | 24–27 in | 5–6 in |
| Larger lounge chair, seat | 25–27 in | 27–30 in | 5–6 in |
| Deep seat back cushion | 23–25 in | 18–24 in tall | 4–6 in, sometimes tapered |
| Sofa seat module | 23–30 in per seat | 24–30 in | 5–6 in |
| Loveseat bench-style seat | 46–52 in | 24–27 in | 5–6 in |
A cover sized 24 x 24 x 5 is not the same as one sized 24 x 24 x 6. A 6-inch cushion in a 5-inch cover will strain the zipper and corner seams; a 5-inch cushion in a 6-inch cover will sag at the edges.
How to Measure for New Covers
- Remove the old cover if possible and measure the foam insert, not the cover.
- Width: measure side to side across the middle, edge to edge.
- Depth: measure front to back across the middle.
- Thickness: measure the edge height at the front and the back; deep seat backs and some seats are tapered.
- Shape: note rounded front corners, T-shaped cushions, or cut-outs around arms.
- Compare to the frame: the seat cushion should be about 0.5–1 inch smaller than the frame opening so it drops in easily.
If the old foam has flattened, measure the frame opening and the original cover rather than the squashed foam. Old foam often loses an inch or more of height after several seasons.
Cover Options Compared
| Cover type | Fit | Price per seat + back set | Best for |
|---|---|---|---|
| Universal stretch cover | Loose, adjustable; wrinkles | $20–$50 | Quick refresh, odd sizes |
| Standard-size zippered cover | Good if dimensions match | $40–$120 | Common 24 x 24 or 25 x 25 seats |
| Made-to-measure cover | Exact, including tapers and corners | $100–$250+ | Premium frames, non-standard shapes |
| Full replacement cushion with cover | Exact with new foam | $120–$300+ | Foam is crushed, moldy or crumbling |
Fabric Choices for Deep Seating
| Fabric | Fade resistance | Water | Feel | Typical lifespan in sun |
|---|---|---|---|---|
| Solution-dyed acrylic (Sunbrella and others) | Excellent | Water-resistant, dries quickly | Soft, canvas-like | Many seasons |
| Olefin | Very good | Does not absorb water | Slightly slick | Several seasons |
| Spun polyester | Fair | Water-repellent finish wears off | Soft | 1–3 seasons |
| Textilene or PVC mesh | Good | Drains fully | Firm, cooler | Several seasons |
Deep seat cushions hold more water than thin dining pads because there is so much foam. If rain is common, pair the cover with a quick-dry or reticulated foam insert, or at least add a water-resistant liner between foam and fabric.
Construction Details That Matter
- Zipper location: along the back edge, ideally wrapping around the sides by a few inches, makes inserting thick foam easier.
- Welting or piping: gives a crisp edge and reinforces seams on boxy cushions.
- Thread: UV-resistant polyester or PTFE-based thread outlasts standard thread, which can rot in the sun before the fabric does.
- Ties or non-slip bottoms: back cushions slide on deep seats; ties or a grippy base reduce that.
- Drain grommets or mesh bottom panels: help water escape from thick cushions.
Refitting Old Foam
New covers on worn foam can look slack. Before ordering, try these fixes:
- Wrap the foam in 1-inch polyester batting to restore an inch of loft and fill corners.
- Add a foam topper: a 1-inch layer of high-density foam glued or wrapped on top lifts a flattened cushion.
- Replace the foam if it crumbles, smells of mildew or does not recover when pressed. Medium-firm foam with a density around 1.8 pounds per cubic foot or higher is a common outdoor seat choice.
Quick Size Decision Guide
| Your cushion | Recommended cover |
|---|---|
| 24 x 24 or 25 x 25, 5 in thick | Standard-size zippered cover in the same size |
| Tapered back cushion | Made-to-measure or a cover listed with front and back thickness |
| Rounded corners or T-shape | Made-to-measure |
| Unusual sizes and a tight budget | Stretch covers, sized up |
| Crushed foam | New cushion inserts, then covers |
Back Cushions Need Their Own Plan
Back cushions on deep seating are where many cover orders go wrong. They are often tapered, thicker at the bottom than the top, or shaped as loose pillows rather than boxed cushions. A boxed cover on a tapered cushion leaves a baggy top edge, while a tapered cover on a boxed cushion pulls tight at the top seam. Measure the bottom and top thickness separately, and if the difference is more than an inch, look for covers listed with both numbers. Loose-pillow backs, common on modern deep seating, are easier: a standard knife-edge pillow cover in the same width and height usually works. If your back cushions slump down the frame, add ties at the top corners or choose covers with a grippy panel on the back face to keep them upright against the frame.
Care Tips
Unzip and wash covers gently and air-dry them, putting them back on slightly damp so they stretch into shape. Spot-clean between washes, store cushions dry in winter, and turn seat cushions over every few weeks so both sides wear and fade evenly.
