How to Measure for Retractable Patio Screens
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How do you measure for a retractable screen?
It depends on whether the screen mounts to the face of the opening or inside it. For a surface mount, add at least 4 inches to the opening width and at least 7 inches to the opening height. For an inside or recessed mount, use the narrowest measurement you find anywhere in the opening — not the average, the narrowest.
That is the answer. The rest of this is about the ways a measurement that felt correct turns out not to be, because custom-made products do not come with a margin for error and this is where DIY projects go wrong far more often than at the drill.
Measuring for a retractable awning is a different process with different rules — that one is covered in its own guide.
Surface mount or inside mount — decide first
Everything downstream depends on this, so settle it before you pick up the tape.
| SURFACE MOUNT | INSIDE MOUNT | |
|---|---|---|
| Where it sits | On the face of the opening, overlapping the trim | Recessed up inside the opening |
| Looks | Visible cassette and tracks | Cleaner, tucked away |
| Measuring | Add 4" to width, 7" to height | Use the narrowest measurement |
| Needs | Enough flat face to land on | Enough depth, and a genuinely square opening |
| Forgiving of | Out-of-square openings | Very little |
Practical advice: if your opening is old, timber-framed, or has settled at all, surface mount. An inside mount in an out-of-square opening is where people discover that a quarter-inch of racking over eight feet is visible from the kitchen.
Measure each opening. All of them. Separately.
Two bays that were framed on the same afternoon by the same crew are routinely different by an inch or more. Houses move. Concrete cures unevenly. A post gets set a little proud.
So: number every opening on a sketch, and measure every one as though it were the only one. Do not measure the left bay and order three of the same. This single shortcut is responsible for more wrong-size custom screens than anything else in the category.
Measure width in three places, height in three places
Top, middle and bottom for width. Left, center and right for height. Write down all six, even the ones that look identical — especially the ones that look identical. The whole point of doing it six times is finding the one that is not.
Then use them according to the mount type. Inside mount: the narrowest width and the shortest height, because the unit has to pass through the tightest point. Surface mount: the widest, plus your clearance, because the tracks have to land on solid face on both sides.
A six-foot level is the other half of this. Check whether the opening is actually square before you trust any of it, and check what the floor is doing along the whole width.
Now look at the floor, properly
This is the step almost everyone skips and it is the one that produces the complaint. Patio floors are pitched on purpose — codes require slab drainage — so the floor under your opening slopes. Pavers settle on top of that. So the hem bar comes down level and meets a floor that does not, and you get a wedge of daylight along one end.
Measure the gap you would get. Level across the opening, measure down to the floor at both ends and in the middle, and note the worst difference. Then specify accordingly: taller hem bar brushes are available in 0.75” and 1.5” for exactly this condition. Order the right one the first time and the problem never exists.
Write down the obstructions too
Sizing is not just width and height. Before you order, note all of this for each opening:
- Available mounting depth at the head
- Columns, posts and how close they are to where a track needs to go
- Trim profiles — a proud casing changes where a surface mount can sit
- Outlets, light fixtures and switches in the mounting zone
- Which side the power is on, because that decides the drive side of the motor
- Doors, and which way they swing
- Where the furniture goes, so nobody is stepping over a side track
Before you place the order
- Measure everything twice, ideally on two different days. Fresh eyes catch a transposed number that tired eyes read straight past.
- Have somebody else read the tape without looking at your list, then compare. This catches more than you would expect.
- Photograph every opening with the tape in the shot. Invaluable if a question comes up later.
- Read the measuring guide for your specific cassette size — 4" and 5" cassettes do not behave identically.
- If anything is unusual — a curve, a slope, a masonry return, a column in the wrong place — phone before ordering. Custom means custom, and a five-minute call is cheaper than a remake.
FAQs
How do you measure for a retractable patio screen?
For a surface mount, add at least 4 inches to the opening width and at least 7 inches to the opening height. For an inside mount, use the narrowest width and shortest height you measure anywhere in the opening. Measure width at top, middle and bottom, and height at left, center and right.
Should I choose surface mount or inside mount?
Surface mount is more forgiving of openings that are out of square and needs a flat face to land on. Inside mount looks cleaner but requires adequate depth and a genuinely square opening. On older or settled structures, surface mount is usually the safer choice.
Why is there a gap under my patio screen?
Patio floors are pitched for drainage, so a level hem bar meets a sloping floor and leaves daylight at one end. Taller hem bar brushes in 0.75 inch and 1.5 inch are made for this condition — measure the worst gap across the opening before ordering and specify accordingly.
Can I measure one opening and order several the same size?
No. Openings framed at the same time routinely differ by an inch or more once a house has settled. Measure each opening separately — this is the most common cause of wrong-size custom screens.
Do 4-inch and 5-inch cassettes measure the same way?
The principle is the same but the specific clearances are not. Use the measuring guide for the cassette size you are ordering rather than applying figures from the other.