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Corrugated vs box profile

Updated: 23 October 2026

You are covering a shed whose roof is closer to flat than to a steep pitch, and the names in front of you are corrugated iron and box profile. Corrugated vs box profile is a choice between a sine wave and a trapezoidal rib. Pitch, cover width and the screw position belong to the maker’s own sheet. Several amazon.co.uk listings here say corrugated and trapezoidal in one title, and those packs are 0.25 mm short sheets, separate from a stated 34/1000. Prices stay on the [corrugated iron sheets comparison](/hub/diy-supplies/corrugated-iron-sheets). Peter F. compared the listings with published UK maker sheets. We did not load a roof. A qualifying purchase can earn a commission at no extra cost to you.

You are covering a shed whose roof is closer to flat than to a steep pitch, and the names in front of you are corrugated iron and box profile.

Our top picks

Harbour Housewares Harbour Housewares anthracite 14-sheet pack

Best overall

Harbour Housewares Harbour Housewares anthracite 14-sheet pack
7.4/10about £57.99
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Mondeer Mondeer dark grey 14-sheet pack

Best value

Mondeer Mondeer dark grey 14-sheet pack
7.3/10about £53.99
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Warmfay Warmfay black 24-sheet pack with screws

Alternative

Warmfay Warmfay black 24-sheet pack with screws
5.7/10about £73.99
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On this page
  1. 1.A wave and a trapezoidal rib
  2. 2.Minimum pitch is the maker’s figure
  3. 3.Where the screw goes
  4. 4.What these amazon packs actually are
  5. 5.Which profile to use when

A wave and a trapezoidal rib

Corrugated steel, as UK merchants use the word, is a repeating wave. Box profile is a trapezoidal rib with a flat pan. Cladco’s 13/3 datasheet quotes a 990 mm cover. Its 34/1000 datasheet quotes a 1000 mm cover and a 34 mm rib. The amazon packs are a third product, about 45–46 cm wide, each stating 0.25 mm. Harbour says classic corrugated. Mondeer, TEOV and Warmfay say both names. Thickness and laps are on the corrugated iron sheets buying guide.

Minimum pitch is the maker’s figure

Cladco’s own table puts corrugated metal at 10° and box profile at 4°. A 200 mm rise over a 2.4 m run is about 5°, as a rule of thumb: under that corrugated figure and just above their box sheet. ColourClad states 4° on its 0.7 mm 13/3, so a wave can be allowed when that seller prints it. These packs print no pitch. A box sheet at 4° is still the wrong fixing if you screw it like a wave.
Harbour Housewares Harbour Housewares anthracite 14-sheet pack

Testsieger

Harbour Housewares Harbour Housewares anthracite 14-sheet pack
7.4/10about £57.99
View offer

Where the screw goes

On a sinusoidal sheet the notes used here put the screw on the crest. On Cladco’s box profile the fixing is in the valley. A wave laps on a crown, and a 34/1000 laps on the edge that keeps the 1000 mm cover. An amazon sheet about 46 cm wide has no stated cover. Crest fixing on a small wavy roof is on how to fit corrugated iron sheets.

What these amazon packs actually are

None of these listings states a 34/1000 code or a 1000 mm cover. They are about 45–46 cm wide at 0.25 mm. Warmfay states 400 screws and washers. One review reports rust spots after about 20 days. A published pitch and a profile code take you outside this set.

Which profile to use when

Under about 10°, a stated box profile from a maker who allows 4° is the sheet those makers point you to. Cladco’s pair is corrugated metal at 10° and 34/1000 at 4°, fixed in the valley. Fix that box sheet on the crest and the 4° figure no longer applies. A 0.25 mm amazon pack inherits none of those figures. Keep one profile on the slope, and leave a listed building or a house roof outside this comparison.

Common questions

Which is better on a nearly flat shed?
On a fall under about 10°, a stated box profile from a maker who publishes 4° is the sheet that maker describes. Cladco puts box profile at 4° and corrugated metal at 10°. ColourClad quotes 4° on its 0.7 mm 13/3, so a wave can be allowed when that seller prints it. These amazon packs state 0.25 mm and no pitch, so the 4° figure stays on the sheet that carries it.
Which looks like traditional corrugated iron?
The sine wave does. Historic Environment Scotland treats corrugated iron as the traditional rural sheet, and a new profile may not match the one on the roof. Box profile is a trapezoidal rib, closer to modern cladding. Harbour says classic corrugated, while Mondeer, TEOV and Warmfay also say trapezoidal. On a listed building, neither profile stands in for consent.
Do they screw in the same place?
Corrugated guides put the screw on the crest. Cladco’s box-profile installation puts the fixing in the valley. A valley hole in a wave sits in the water channel, and a crest-only fixing ignores a box sheet meant to be fixed in the pan. Use the note for the sheet you bought. Warmfay is the listing here that states 400 screws and washers.
Is box profile stronger?
Thickness and support decide it, alongside the rib. A 34 mm rib in the 0.7 mm gauge Cladco lists for 34/1000 roofing is a different section from a 0.25 mm wave. No listing here states a snow load, a purlin spacing or a span. Buy the gauge and the supports that maker states for your roof.
Can I mix them on one roof?
Keep one profile on each slope. Cladco quotes 990 mm cover on 13/3 corrugated and 1000 mm on 34/1000, while these amazon sheets are about 45–46 cm with no stated cover after the lap. The side lap misses the rib, and the screw moves from crest to valley. Order the laps from the maker of the sheet you are laying.
Does a conservation setting change the choice?
It does when the roof is historic corrugated iron or the building is listed. Historic Environment Scotland advises repairing the sheet rather than covering corroded iron, because a new profile may not match. A new corrugated sheet or a box profile does not stand in for consent. For a house roof, leave the set. If an old shed skin might be asbestos cement, have it identified before you drill.

Related pages

Corrugated sheets for a shed roof

Corrugated iron sheets

Best corrugated roofing sheets: shed, lean-to or skip

Corrugated iron sheets: thickness, laps and screws

How to fit corrugated iron sheets on a small shed roof

Sources

Public UK sources and the amazon.co.uk listings compared on this page. Updated 22.10.2026.

  1. Planning Portal: Outbuildings (retrieved 22.10.2026)
  2. Planning Portal: Building regulations for an outbuilding (retrieved 22.10.2026)
  3. legislation.gov.uk: Class E outbuildings (retrieved 22.10.2026)
  4. Cladco: 13/3 corrugated datasheet (retrieved 22.10.2026)
  5. Cladco: Corrugated installation guide (retrieved 22.10.2026)
  6. HSE: Fragile surfaces (retrieved 22.10.2026)
  7. HSE: Using the right type of PPE (retrieved 22.10.2026)
  8. Briarwood: 13/3 declaration (retrieved 22.10.2026)
  9. Cladco: 13/3 galvanised corrugated roofing sheets (retrieved 22.10.2026)