Lightweight Roofing Materials for Old Buildings

Mr Quyen - Santiago. Posted 14/11/2026

Santiago's ASA/PVC roof tile sheet weighs about 5.4 kg per m² of roof (about 1.1 lb per sq ft) at 2.5 mm, and a 2.5 mm corrugated sheet about 5.2 kg per running metre. That is far lighter than clay or concrete tile, but a light roof still needs a frame that a builder or engineer has checked, purlins less than 700 mm apart and fixings that suit local wind rules.

Steel roof frame built on top of a house, Vietnam

Steel roof frame built on top of a house, Vietnam

What counts as a lightweight roofing material?

On a roof, weight means dead load: what the rafters, trusses and walls carry every day before wind, rain or a person on a ladder adds anything. Clay and concrete tiles are much heavier per square metre than any sheet. Old timber frames were usually sized for whatever covering went on first, so a lighter covering takes load off them, and a heavier one needs an engineer before anything else is decided.

Santiago's sheets are solid ASA/PVC with no metal in them, co-extruded in four layers: an ASA top layer, virgin PVC, a PVC core and a milky-white PVC base. The weights below are for 2.5 mm, the minimum Santiago supplies for roofs.

Product (2.5 mm)	Cover width	Weight
Roof tile sheet	0.96 m (3.15 ft)	About 5.4 kg per m² of roof (about 1.1 lb per sq ft)
5-wave corrugated sheet	1.00 m (3.3 ft)	About 5.2 kg per running metre (about 3.5 lb per running foot)
6-wave corrugated sheet	0.95 m (3.1 ft)	About 5.2 kg per running metre
11-wave corrugated sheet	1.00 m (3.3 ft)	About 5.2 kg per running metre

How much does a lightweight roof weigh in total?

Multiply the roof area by 5.4 kg for the tile sheet. Use the area of the slopes, not the floor plan, because a pitched roof is always larger than the room below it.

Roof	Roof area	Tile sheets only
Carport or porch	20 m² (215 sq ft)	About 108 kg (240 lb)
Single-storey extension	40 m² (430 sq ft)	About 216 kg (475 lb)
Small house	120 m² (1,290 sq ft)	About 650 kg (1,430 lb)

Screws, ridge pieces and any new purlins come on top of that. Single sheets are easy to handle: a tile sheet cut to 4.38 m, which is 20 tile steps of 219 mm, covers about 4.2 m² and weighs about 23 kg (50 lb). Two people can pass it up a ladder or scaffold without a crane, which matters on narrow streets and in old town centres.

Roof sheets being lifted up onto a roof frame, Vietnam

Roof sheets being lifted up onto a roof frame, Vietnam

Is a lightweight roof safe on an old building?

Light weight helps an old frame only if the frame is sound. Before ordering, ask a builder or structural engineer to look at:

Rot, termite damage or splits in timber rafters and wall plates
Rust in steel trusses, bolts and brackets
Cracks in the walls that carry the roof
How the frame is tied down to the walls
Where new purlins will sit and whether those points can take the load

Light weight has a second side. A heavy tile roof partly holds itself down, while a sheet roof relies on its screws and on the tie-downs of the frame to resist wind uplift. Santiago's own fixing standard is 70 mm screws through the top of the wave into a purlin, 4 – 5 screw sets per m², but Santiago gives no structural or wind rating. In storm-prone areas your installer sets the fixing pattern under local building codes.

If the old roof is asbestos cement, do not take it off yourself. Licensed specialists remove it under local rules, and the new roof goes on afterwards.

Which lightweight roofing materials suit which old building?

Material	Weight	Look	Rust	Points to know
ASA/PVC roof tile sheet	Light sheet	Rows of curved tiles	None, no metal	Purlins under 700 mm, slope 20 – 45%
ASA/PVC corrugated sheet	Light sheet	Plain waves	None, no metal	Workshops, farm buildings, stores, sheds
Coated metal sheet	Light sheet	Plain or pressed tile pattern	Can rust where the coating is cut or scratched	Louder in rain and hotter underneath than ASA/PVC
Polycarbonate sheet	Light sheet	Clear or tinted	None	Lets light and heat through; used for skylights and canopies
Clay or concrete tile	Heavy	Individual tiles	None	Check the dead load with an engineer first

Compared with bare metal sheet, Santiago's tests show 6 – 8 °C lower temperature under the roof and about 80% less rain noise. Santiago has not tested against clay or concrete tile, so no figure is given for that comparison.

How do I plan purlins for lightweight roofing tiles on an old frame?

Old roofs were often battened for small clay tiles, or set out with wide purlin spacing for metal sheet. Neither layout fits a tile sheet. Santiago's tile sheet needs one purlin under the foot of a tile step, which gives spacings of 440 or 660 mm.

Measure each slope from eave to ridge along the rafter.
Fix the top purlin 15 – 18 cm (6 – 7 in) below the ridge.
Space the other purlins at 660 mm (26 in) or 440 mm (17 in) down to the eave; never wider than 700 mm (27.5 in).
Order sheet lengths in 219 mm (8.6 in) steps so each sheet ends on a full tile.
Check the slope: 20 – 45%, about 11 – 24°. Below 20% the roof does not shed water well and Santiago does not recommend it.
Pre-drill 6 mm holes at the top of the wave so the sheet can move with heat.

Light roof frame on a building site with grey tile sheets, Vietnam

Light roof frame on a building site with grey tile sheets, Vietnam

Is lightweight plastic roofing durable enough?

Light does not mean flimsy. The sheet has a bending strength above 1,000 N. The ASA top layer showed no colour change after 2,000 hours of artificial UV, the colour is rated for 30 years and the real service life is 25 – 30 years. Santiago gives a 10-year warranty on 2.5 mm and thicker sheets installed as it recommends. The sheet is not a walking surface, though, so plan how maintenance will reach gutters and chimneys.

Installers working on a red tile-sheet roof, Vietnam

Installers working on a red tile-sheet roof, Vietnam

How does a light ASA/PVC sheet behave when bent and cut?

Mr Quyen stands in the Santiago factory in Vietnam and bends and cuts beige and orange sheets with metal shears while he explains in English, with captions, how the sheet holds up. Bending by hand is a demonstration; a roof still needs purlins less than 700 mm apart.

Bending and cutting test on Santiago ASA/PVC sheets (Santiago video on YouTube).

Santiago – a leading exporter of ASA/PVC roofing from Vietnam

Santiago roofing is produced and loaded into containers at our factory in Vietnam. It has been exported to India since 2023, Thailand since 2024 and the USA since 2025. Every export shipment comes with a commercial invoice, packing list, bill of lading and a certificate of origin (C/O) issued by Vietnam's Ministry of Industry and Trade, which importers use to claim the duty preference of their trade agreement.

Item	Details
HS code	3925.90.00 (ASA/PVC roofing sheets)
Certificate of origin	Form D (ASEAN), Form AI (India), Form AK / VK (Korea), Form AJ / VJ (Japan), Form VC (Chile), CPTPP proof of origin
Shipped from	Vietnam, by container

Certificate of origin Form AI (ASEAN–India) for Santiago ASA/PVC roofing sheets, HS 39259000, certified on 24 September 2026. Buyer details are hidden.

Certificate of origin Form AI (ASEAN–India) for Santiago ASA/PVC roofing sheets, HS 39259000, certified on 24 September 2026. Buyer details are hidden.

The Santiago team beside a loaded export container at the factory, November 2024

Loading Santiago roof tiles into an export container

Frequently asked questions

What is the lightest roofing material for an old house?

Sheet materials are lighter than clay or concrete tiles. Santiago's ASA/PVC tile sheet weighs about 5.4 kg per m² of roof at 2.5 mm and gives a tile look; have the frame checked by a builder or engineer before choosing.

Can I put lightweight roofing tiles on an old timber frame?

Often yes, once rot, insect damage and tie-downs have been checked. Santiago's tile sheet needs purlins less than 700 mm apart (440 or 660 mm), so new purlins are usually added to an old frame.

Do lightweight roofing sheets blow off more easily?

A light roof depends on its screws and the frame's tie-downs to resist wind uplift. Santiago uses 70 mm screws, 4 – 5 sets per m², through the top of the wave, but the fixing in your area is set by your installer under local codes. Santiago gives no wind rating.

How much does a lightweight plastic roof weigh for a 100 m² house?

With Santiago's 2.5 mm tile sheet, about 540 kg (about 1,190 lb) of sheet for 100 m² of roof slope, plus screws, ridge pieces and purlins.

Does lightweight plastic roofing fade or rust?

ASA/PVC sheets do not rust because they contain no metal. Santiago's ASA top layer showed no colour change after 2,000 hours of artificial UV, and the colour is rated for 30 years.