Roof Painting or Roof Replacement: How to Tell Which You Need

A tired-looking roof is not necessarily a failing one. Plenty of roofs that look past it are structurally sound and simply need cleaning and recoating, and plenty that look acceptable from the ground are not worth spending money on. The difference is worth establishing before you get quotes, because it changes the number by an order of magnitude.

When painting is the right answer

Painting makes sense when the roof material is sound and the problem is the coating. Typically that means:

• The surface is chalky, faded or patchy, but the sheets or tiles are intact.
• There is surface rust in spots, but no perforation and nothing soft.
• Fixings are sound, and flashings and penetrations are in reasonable order.
• There are no leaks, or the leaks are traceable to flashings that can be repaired.

A recoat in this situation restores the appearance and adds protection, and it is far cheaper than replacement.

When replacement is the honest answer

• Rust has gone through. Once there are perforations, or the metal is soft and flexes underfoot, coating it is putting paint over a hole.
• Widespread corrosion at the laps and fixings. Surface rust in a few places is repairable. Rust at every fixing across the roof is a roof at the end of its life.
• Persistent leaks that are not flashing related. Paint is not a waterproofing system.
• Cracked or crumbling tiles across the roof. Individual tiles can be replaced. A roof where the tiles have gone porous cannot be rescued with a coating.
• The roof is near the end of its expected life anyway. Spending on a recoat that will need redoing in five years, on a roof that needs replacing in seven, is money spent twice.

A reputable contractor will tell you when replacement is the better spend, even though it is not work they are quoting for.

It depends on what the roof is made of

Long run steel and Colorsteel is the most common roof in Wellington and generally the most straightforward to recoat. It needs a thorough wash to remove chalked coating, salt and lichen, treatment of any rust back to sound metal, the correct primer for the substrate, and a topcoat system made for roofs. Coatings for factory-finished steel are specific, and using a general exterior paint is a false economy.

Concrete tile takes a coating well once it is properly cleaned, and a recoat can transform the appearance. The key is that the tiles must be sound. Concrete tiles become porous with age, and a coating on a tile that is breaking down does not last.

Clay tile is generally best left alone. It does not need protection and coatings tend not to stay on it.

Membrane and butynol roofs are a specialist area with their own coating systems and are not a standard roof painting job.

What a proper roof repaint involves

Wash and treat, so that lichen and moss are killed rather than painted over. Mechanically treat any rust and prime it. Repair or replace failed fixings and seals. Prime the whole surface where the system requires it. Then apply the topcoats, usually two, at the coverage rate the manufacturer specifies.

Spouting and flashings are usually done at the same time, since access is already sorted.

Safety, and why this is not a DIY job

Roof work is height work on a sloping, often slippery surface, frequently in Wellington wind. It needs edge protection or a harness system and proper access. It is also the job where a fall does the most damage. This is one to hand over.

The Wellington factors

Salt-laden air on coastal and harbour-facing suburbs accelerates corrosion, particularly at cut edges and fixings. Shaded, south-facing roof planes grow lichen readily, and lichen holds moisture against the surface. An annual or twice-yearly wash extends the life of a roof coating more than any other single thing.

Getting an honest assessment

We will get up and look at the roof properly rather than assess it from the ground, and tell you if painting is not the right spend. Get in touch, or read more about our roof painting work in Wellington.