UPVC Roofing Accessories and PVC Ridge Cap Guide | Santiago

Mr Quyen - Santiago. Posted 14/11/2026

Ridge pieces stacked in a factory, Vietnam

What does each UPVC roofing accessory do?

Every piece is made in the sheet colours: dark grey, red, blue, orange and chocolate as standard, and green, white and purple to order. The pieces travel in the same container as the sheets, so order them together; a few missing ridge caps ordered later mean a second shipment for a handful of pieces.

Is UPVC roof capping the same as a ridge cap?

Usually, yes. In the UK and Ireland "capping" or "ridge capping" is the everyday word for the piece along the top of the roof; in the US and many other markets people say "ridge cap". Some builders also call any edge trim "capping". When you ask for a quotation, name the line each piece is for: ridge, hip, edge or wall. Then nobody has to guess.

Grey ridge caps on a tile-sheet roof, Vietnam

Which accessories does each roof shape need?

Many houses combine shapes, for example a hip roof with a lean-to porch against one wall. List each roof face and each line, and the accessory list follows from it.

How many accessories should I order?

• Ridge caps, hip ridges, wall flashing and edge pieces: measure each line along the roof, divide by the usable length of one piece after its overlap (given on the product page and on the quotation) and round up.
• Three-way pieces: one at each point where the ridge meets two hips, so two on a plain hip roof.
• Four-way pieces: one at each peak where four hips meet.
• Ridge terminals: one for each open end of a ridge.
• Screw caps: one for every screw. The sheets need 4 – 5 screw sets per m², and the ridge, hip and edge pieces need their own screws on top of that.
• A spare piece or two per line covers a bad cut, which matters most on a remote site.

Take a gable roof 10 m long with sheets of 4.818 m on each side. The roof area is 2 × 10 × 4.818, about 96 m², so the sheets need about 390 – 480 screw sets and the same number of caps. Add the ridge caps along 10 m, two ridge terminals, edge pieces along the four gable edges and the screws for all of them. Santiago's accessory checklist, linked below, works through a full hip roof piece by piece.

Ridge caps in several colours on racks, Vietnam

In what order are the accessories fitted?

1. Check the frame: purlins less than 700 mm apart (440 or 660 mm for the tile sheet) and the top purlin 15 – 18 cm below the ridge, so the ridge cap has something solid to screw into.
2. Lay the sheets, lapping one wave sideways, with screws through the top of the wave over a purlin in pre-drilled 6 mm holes and an ASA cap on each screw.
3. Fit the vertical wall flashing over the top row of sheets where a slope meets a wall.
4. Fit the eave sealing tile (side wall flashing, left and right) where a side edge of the roof runs along a wall, and the eave drip tile along the eaves.
5. Fit the hip ridges from the bottom of each hip upwards, each piece lapping over the one below so water runs over the joint, not into it.
6. Fit the ridge caps along the ridge, starting from the end away from the usual wind so each lap faces away from it.
7. Fit the three-way or four-way pieces over the meeting points of the ridge and hips.
8. Close the open ends with ridge terminals.
9. Check the finished roof from the ground and from a ladder: every screw should have its cap, and every line should be closed at both ends.

How are the joints sealed?

Laps and screws do most of the sealing on a sheet roof, not sealant. Each lap points downhill or away from the wind, every screw sits on a high point where water does not flow, and the washer under the ASA cap closes the hole. Stop tightening when the washer is snug: over-tightening dents the sheet and the piece above it. The 6 mm pre-drilled hole gives the screw room as the plastic moves with heat.

Sealant has one regular job: the top edge of a wall flashing, where it meets the wall, is sealed to the wall with outdoor sealant or tucked under a cover strip. Do not use sealant to fill a gap that a wrong lap or a missing piece left; fix the lap or fit the piece.

Grey hip ridge pieces, Vietnam

What about corrugated PVC ridge caps?

The accessory set above is made for the tile sheet. For a roof of 5, 6 or 11-wave sheets, ask Santiago which ridge and edge pieces suit the profile before you order, and send the roof drawing with the request. Screw caps fit both: the fixing rules, through the top of the wave over a purlin, are the same for every profile.

Which pieces go on a finished tile-sheet roof?

Mr Quyen stands among stacks of brown tile sheets in the Santiago factory, then walks with a colleague along a finished grey tile roof with its ridge and edge pieces near the gutter. Installers carry a grey tile sheet into place.

Santiago uPVC tile sheets from the factory to the roof (Santiago video on YouTube).

More short videos on accessories

Two more English shorts from the Santiago YouTube channel. Each one is about a minute or less.

Frequently asked questions

What accessories do I need for a UPVC roof?

It depends on the roof shape. A gable roof needs a ridge cap, two ridge terminals, edge pieces and screw caps; a hip roof adds diagonal ridges, two three-way pieces and terminals at the foot of each hip; a pyramid roof uses a four-way piece at the peak.

What is a PVC ridge cap?

The piece that covers the joint along the top of the roof where two slopes meet. Santiago makes it in the same colours as its ASA/PVC tile sheets.

How many ridge caps do I need?

Divide the ridge length by the usable length of one ridge cap after its overlap, shown on the product page and quotation, and round up. Add a spare for a remote site.

In what order are roof accessories fitted?

Sheets first, then wall flashing and edge pieces, then hip ridges from the bottom up, then ridge caps, then three-way or four-way pieces, and the ridge terminals last.

Do roof accessories need sealant?

Mostly no. Correct laps and screws on the top of the wave with ASA caps keep water out. Sealant is used along the top edge of a wall flashing where it meets the wall.

Read more

• Ordering roof tile accessories: checklist and worked example
• Eave sealing tile or wall flashing: which edge piece goes where
• Pyramid roofs and gazebos: tile accessories
• Screws and ASA caps: fixing through the top of the wave
• Top ridge cap for ASA/PVC roof tiles

Updated 03/11/2026. Santiago Import Export Co., Ltd, Vietnam. WhatsApp +84 935 391 495 (Mr. Quyen), hotline +84 965 437 316 (Mrs. Ly), email salessantiagoroofing@gmail.com.