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Window seal: name the gap before you buy

Updated: October 2026

You can feel the draught on a shut casement, with a foam roll in one hand and a rubber coil in the other. A window seal works only when it matches that opening, and the wrong thickness stops the handle locking. Name the gap, measure it in millimetres, then match stick-on or push-in. Products Compared checked nine amazon.co.uk listings on 15 October 2026, with no laboratory test. A qualifying purchase can earn a commission at no extra cost to you. The nine prices sit on our [window seal](/hub/door-and-window-security/window-seal) comparison.

You can feel the draught on a shut casement, with a foam roll in one hand and a rubber coil in the other. A window seal works only when it matches that opening, and the wrong thickness stops the handle locking.

Our top picks

Storm Patrol Storm Patrol uPVC gasket, 25 m, black

Best overall

Storm Patrol Storm Patrol uPVC gasket, 25 m, black
7.5/10about £20.18
View offer
YANKUIRUI YANKUIRUI D-profile foam seal, 6 m, white

Rank 2

YANKUIRUI YANKUIRUI D-profile foam seal, 6 m, white
8.6/10about £4.49
View offer
UPSEN UPSEN D-profile foam seal, 10 m, white

Best value

UPSEN UPSEN D-profile foam seal, 10 m, white
8.3/10about £4.99
View offer
On this page
  1. 1.Name the gap before you name the material
  2. 2.Measure the closed gap in millimetres
  3. 3.Stick-on rebate or push-in groove
  4. 4.Length, colour and the claims to ignore

Name the gap before you name the material

Choose the window seal from the opening, not from the colour of the coil. A casement rebate can take soft D-profile foam or a firmer rubber D. Historic England's HEAG084 says one compression size covers only a narrow range, and foam is cheaper and shorter-lived than a brush or wiper strip. Hard rubber in a groove needs a push-in gasket whose foot matches that slot. A sliding sash needs a brush. Energy Saving Trust says foam is the wrong tool there, because the gap changes as the sash travels.

Measure the closed gap in millimetres

Measure the shut gap in millimetres on the hinge side and the handle side. Where a ruler cannot reach, Seals Direct's rule of thumb is Blu Tack squashed in the rebate and then measured. Try a 50 mm piece on the fixed frame, as the Centre for Sustainable Energy describes, until a plastic card sits snug. On 15 October 2026 YANKUIRUI stated 3–6 mm, UPSEN about 3.5–5 mm, and Esufeir 2.5–6 mm. GUKOY, WanderGo, wordmouk and Tarqite stated no gap. Too big a strip stops the window closing.
Storm Patrol Storm Patrol uPVC gasket, 25 m, black

Testsieger

Storm Patrol Storm Patrol uPVC gasket, 25 m, black
7.5/10about £20.18
View offer

Stick-on rebate or push-in groove

Stick-on foam suits a rebate with no usable groove. A push-in gasket needs a slot that can still grip a foot. GUKOY at about £6.99 is flat 6 mm by 3 mm tape with no stated gap, so it will not fill a 5 mm rebate. Esufeir is firmer, so an uneven rebate can hold the sash off even inside 2.5–6 mm. Storm Patrol at about £20.18 states frames of 3–5 mm. Tarqite pushes in, states no gap, and has nine reviews. A sample foot continues on replacing a uPVC window seal. With no sound groove, see foam window seal or gasket.

Length, colour and the claims to ignore

Measure both sides, the head and the sill, then add a short offcut at each corner. A casement about 1.2 m by 0.9 m is about 4.2 m before that waste. YANKUIRUI's 6 m is two 3 m pieces and UPSEN's 10 m is two 5 m lengths. One Bynsaer review found about 3 m before the roll was split. Esufeir and Tarqite print length fields that disagree. Who should take which listing is on our best window seal page.

Common questions

What gap is a D-profile foam seal actually for?
A D-profile foam seal suits a narrow, even gap on a closing casement. On 15 October 2026 YANKUIRUI stated 3–6 mm, Bynsaer stated 3–5 mm, and UPSEN stated about 3.5–5 mm. Listings that state no gap do not inherit those bands.
How do I measure a closed window gap in millimetres?
Shut the window and measure the gap in millimetres in more than one place. Where a ruler cannot reach, squash Blu Tack in the rebate and measure it, which Seals Direct offers as a practical check. Then try a 50 mm piece on the fixed frame until a plastic card sits snug. If that piece stops the handle locking, the strip is too thick.
Should I buy stick-on foam or a push-in gasket?
Choose stick-on foam or rubber when the rebate has no usable groove. Choose a push-in gasket when the old rubber sits in a slot that can still hold a foot, and try that foot on a sample first. Storm Patrol states frames of 3–5 mm. Tarqite also pushes in and states no gap.
How much length do I need for one casement?
Measure both sides, the head and the sill, then add a short offcut at each corner. A casement about 1.2 m by 0.9 m is about 4.2 m before that waste. YANKUIRUI's 6 m is two 3 m pieces. One Bynsaer review found about 3 m before the roll was split.
Can I use the same strip on a sash window?
Use a brush on a sliding sash. Energy Saving Trust says foam is the wrong tool there, because the gap changes as the sash moves. A draught between the glass and the bead belongs with a fitter.
Why do two length fields on one listing disagree?
Esufeir's title says 6 m and the unit count says 1 m. Tarqite's title says 6 m, the unit count says 8 m, and the item-length field says 80 cm. Those figures cannot all be the coil in the packet. The Consumer Rights Act 2015 requires goods to match their description, so pick a coil whose pieces are stated, such as YANKUIRUI's two 3 m lengths.
Does a window seal count as a security upgrade?
A window seal is a draught strip, and the lock remains the security hardware. None of the nine amazon.co.uk listings here shows a BS EN 12365 class, and the coil sits outside PAS 24. It can ease a draught on a casement that still locks. It does not replace a handle that fails to meet the keep.

Related pages

How to fit a stick-on window seal

Window seals

Best window seal for a groove or a stick-on rebate

Foam window seal or a gasket: which one should you buy

Replace a uPVC window seal when the rubber is hard

Sources

Public UK sources named in the research digest. Listing prices and ratings are the amazon.co.uk figures saved on 15 October 2026.

  1. Energy Saving Trust — Draught-proofing (retrieved October 2026)
  2. Centre for Sustainable Energy — DIY draught-proofing (retrieved October 2026)
  3. GOV.UK — Approved Document F (2026) (retrieved October 2026)
  4. BSI — BS EN 12365-1:2003 gasket and weatherstripping (retrieved October 2026)
  5. Seals Direct — How to measure a replacement glazing gasket (retrieved October 2026)
  6. Fixtrade — How to replace the rubber seal on uPVC windows (retrieved October 2026)
  7. Historic England — HEAG084 Draught-proofing windows and doors (retrieved October 2026)
  8. Consumer Rights Act 2015 (retrieved October 2026)