Deep Seat Outdoor Cushions for Canadian Decks and Patios: Sizes and Measuring

Quick answer: A deep seat outdoor cushion is usually 24″ to 30″ deep, where a standard seat is about 18″ to 22″. Measure your frame from the front edge to the back rail. If it is 24″ or more, you need deep seat cushions, usually 4″ to 5″ thick, plus back cushions to fill the space behind you.

The Canadian deck has changed. It used to be a few folding chairs and a barbecue. Now it is often a proper outdoor living room: a low sectional, a coffee table, string lights and a fire table for cool September evenings. The furniture that makes that look work is deep seat furniture, and the piece that makes deep seat furniture comfortable is the cushion.

Deep seat frames are also the hardest to fit with off-the-shelf cushions. Every maker builds to slightly different dimensions, and a cushion that is an inch or two short leaves a gap you notice every time you sit down. Here is how to size them properly.

Deep seat vs standard seat: what is the difference?

The difference is depth, front to back. A standard outdoor dining chair or patio chair seat is usually 18″ to 22″ deep. You sit upright, feet on the deck, ready to eat. A deep seat frame is usually 24″ to 30″ deep. You sit back, knees lower, and lean into a back cushion. It is the difference between a chair you perch on and a sofa you sink into.

Thickness changes too. A dining chair pad is typically 2″ to 3″. A deep seat cushion is usually 4″ to 5″, which gives that full, upholstered look and enough foam to stay comfortable through a long evening.

How to tell if your furniture is deep seat

Measure from the front edge of the seat frame straight back to the back rail. Ignore your old cushions.

• 24″ or more: deep seat. You will want deep seat cushions plus back cushions.
• 18″ to 22″: standard seat. A standard seat cushion is the right fit.
• In between: measure carefully and order to your numbers. That is what made-to-measure is for.

How to measure deep seat cushions, step by step

Work in inches with a metal tape, and round to the nearest quarter inch. Write the numbers on a sketch of the frame as you go.

1. Seat width

Measure across the seat from the inside of one arm to the inside of the other. Measure at the front and at the back. Many deep seat frames are slightly narrower at the back, and if your two numbers differ, give us both.

2. Seat depth

Measure from the front edge of the frame to the back rail. If you plan to use back cushions, you still order the seat to the full depth of the frame. The back cushion sits on top of the seat at the back.

3. Thickness

Check the height of the seat rail or lip that holds the cushion. A frame built for a 4″ cushion usually has a rail of about that height. For most deep seat furniture, 4″ to 5″ is right. If the seat still feels too deep once you sit in it, a thicker back cushion brings you forward. Our cushion thickness and foam guide helps you choose.

4. Back cushions

Measure from the seat surface (the top of where the seat cushion will sit) up to where you want the back cushion to stop, usually at or just below the top of the frame. Measure the width edge to edge across each section.

5. Corners and odd shapes

Corner pieces on sectionals are often square, wedge-shaped or have a cut corner. Curved front rails and angled arms are common too. For anything that is not a simple rectangle, trace the shape on paper and send it as a template. Template and custom shapes are made in 5–6 weeks.

6. Measure every section

Sectional pieces that look identical are often slightly different. Measure each one, and label your sketch so we know which cushion goes where.

For more detail and diagrams, see our guide to measuring for custom cushions in inches.

Box edge or knife edge?

Deep seat cushions almost always look best box edged, with a separate side panel (the boxing) between the top and bottom. The cushion keeps its square, tailored shape and sits flush in the frame. Knife-edge cushions, where top and bottom meet at a single seam, suit thin pads and dining chairs better. Piping along the edges is optional and adds a crisp outline, especially in a contrasting colour.

Fabric for a deck that sees real weather

A deep seat sectional uses a lot of fabric, so whatever you choose is going to be on show. If the fabric fades after one summer, every cushion fades together.

Sunbrella is our most popular choice for deep seat outdoor cushions. It is solution-dyed acrylic, so the colour holds in full sun, most of it is water-repellent and the covers unzip and go in the washing machine. Sunbrella backs its fabric with a 5-year warranty. If your sectional is fully exposed to rain, Sunbrella's waterproof marine and Rain ranges are worth a look. We offer more than 160 Sunbrella colours. Our guide What is Sunbrella fabric, and is it worth it in Canada? covers the details.

Foam for deep seat outdoor cushions

• Dryfast: the right choice for a sectional on an open deck that stays out through summer storms. Water drains straight through the open-cell foam, so the cushion dries quickly and does not stay soggy. Warrantied for 5 years.
• HD36-R: a medium, supportive foam for deep seat furniture on a covered porch, in a screened room or under a pergola roof. Warrantied for 7 years.
• Lux-R: a firmer seat for people who prefer more support. Warrantied for 7 years.
• Super Soft: back cushions only, for a softer lean-back feel. Never use it for seats. Warrantied for 3 years.

Our foam is CertiPUR-US certified. Our guide to patio and deck cushions for Canadian summers has more on UV, rain and fast-drying foam.

Living with deep seat cushions in Canada

• After a storm, stand cushions on edge so they drain, even with Dryfast foam.
• Use the ties. Matching fabric ties come standard and stop back cushions blowing off the deck in a gust.
• Bring them in for winter. Clean, dry and store indoors before the first hard frost. Our guide to storing outdoor cushions over winter explains how.
• Order early. Ordering over the winter means cushions are ready for the May long weekend.

Ordering deep seat cushions to Canada

Start with the deep seat cushion builder, or browse deep seat outdoor cushions for ideas. There is no minimum order, so you can replace a single cushion or a whole sectional. Every cushion is cut within ±0.5″ of your size, with a free remake if we miss. Standard shapes are made in 2–3 weeks. Canadian orders ship with duties and GST/HST paid, so nothing is due on delivery. See ordering custom cushions to Canada for more.

Frequently asked questions

How deep is a deep seat outdoor cushion?

Usually 24″ to 30″ deep, compared with about 18″ to 22″ for a standard seat. Measure your own frame, because makers vary.

How thick should deep seat cushions be?

Most are 4″ to 5″ thick. Thinner cushions look flat on a deep frame and feel hard after an hour.

Do deep seat cushions need back cushions?

Almost always. A deep frame leaves space behind you, and a back cushion fills it and brings you forward to a comfortable position.

Should I measure my old cushions or the frame?

Measure the frame. Old cushions shrink and flatten over time and will give you the wrong numbers.

Which foam is best if my sectional stays out in the rain?

Dryfast foam. It drains water instead of holding it, so the cushion dries quickly after a storm.