Metal roof waterproofing Cape Town covers IBR, corrugated and other sheet roofing. Sheet roofs rarely fail across the sheet. They fail at fasteners, laps, ridges and flashings.
That changes the work: it is sealing, reinforcing and coating rather than laying a membrane. For other roof types see roof waterproofing, and for the full range Waterproofing Cape Town.
Send photos of the roof from above if you can, and note the roof age and whether it is near the coast.
Get a Metal Roof QuoteWhere Sheet Roofs Fail
| Location | What goes wrong |
|---|---|
| Fasteners | Perished washers, corroded screws, fixings backed out by thermal movement. The most common source. |
| Side laps | Driven rain forced up between overlapping sheets against gravity. |
| End laps | Where sheets join along their length. Needs sealant and adequate overlap. |
| Ridge and hip caps | Sealing and fixing at the apex, exposed to wind uplift. |
| Flashings | At walls, parapets and chimneys. Corrosion and lifting. |
| Corrosion | Surface rust progressing to perforation, worst at fixings and cut edges. |
| Translucent panels | Age faster than the steel around them and become brittle. |
Corrosion and Coastal Exposure
Salt air is the dominant factor on the Atlantic Seaboard, in Table View, Milnerton, Blouberg, Muizenberg and the Helderberg coastline. Salt is hygroscopic: it holds moisture against the steel long after rain has stopped, so corrosion continues on dry days.
Fasteners go first, because they are a different metal in contact with the sheet and they concentrate stress. Cut edges and the underside of overlaps follow. Any coating job on a coastal roof that does not deal with the fasteners is spending money on the wrong surface.
The Coating Process
- High-pressure clean to remove chalking, salt deposits, lichen and loose material.
- Replace failed fasteners and washers, and tighten backed-out fixings.
- Wire brush or grind rusted areas back to sound metal.
- Apply rust treatment or a suitable primer to bare and treated steel.
- Seal and reinforce laps, fasteners, ridges and flashings with tape or fabric.
- Apply the coating at the specified thickness and coat count.
Coating over unreplaced fasteners is the standard shortcut on sheet roofs. The coating looks perfect and the roof keeps leaking, because the water is going past the screws rather than through the sheet.
Metal Roof Waterproofing Cape Town Prices
| Job | Indicative range | What moves it |
|---|---|---|
| Sheet roof coating system | R120 – R280 per m² | Preparation and coat count. |
| High-pressure clean and prep | R25 – R70 per m² | Roof condition. |
| Fastener replacement | R25 – R60 each | Type and access. |
| Rust treatment | R60 – R180 per m² | Extent of corrosion. |
| Lap sealing and reinforcement | R80 – R220 per linear metre | Tape or fabric system. |
| Ridge and flashing sealing | R150 – R400 per linear metre | Detail and access. |
| Replace corroded sheeting | R280 – R650 per m² | Supplied and fitted. |
| Typical 120 m² sheet roof | R18,000 – R38,000 | Prepared, fasteners done, coated. |
These are indicative market ranges, not a quotation. They are compiled from published South African waterproofing and roofing pricing to give you a starting point for budgeting. They are not the rate card of any company on this platform.
Compare quotes on the system specified, the number of coats, what preparation is included and what the guarantee covers. A rate per square metre means nothing until you know what the rate covers.
Coastal roofs benefit from being assessed before the coating is quoted. The fastener count often changes the price more than the area does.
Get a Metal Roof QuoteWind and Metal Roofs
Cape Town's summer south-easter and winter north-wester both put uplift on sheet roofs. Uplift works fixings loose over time, and a loose fixing admits water long before it looks like a problem from the ground.
Wind-driven rain is the other mechanism. Water is pushed sideways and upwards into side laps, which is why sheet roofs so often leak in one wind direction only. Sealing and reinforcing the laps addresses that; more coating does not.
Related Services
Frequently Asked Questions
How much does metal roof waterproofing cost in Cape Town?
Coating a sheet roof generally runs R120 to R280 per square metre including preparation and lap reinforcement. Replacing fasteners is around R25 to R60 each, and sealing ridge and flashing runs R150 to R400 per linear metre.
Why do metal roofs leak at the screws?
Because the rubber washer under the screw head perishes with UV and heat, and the screw itself corrodes or backs out with thermal movement. On a roof with thousands of fixings, fasteners are the most common leak source by a wide margin.
Can a rusted roof be coated?
If the rust is surface-level and the sheeting still has structural thickness, yes: wire brush or grind it back, treat with a rust converter or primer, then coat. Where rust has perforated the sheet, that section needs replacing first.
What is the best coating for an IBR roof?
Bituminous aluminium coatings and acrylic roof coatings are both used, with reinforcing fabric or tape over the laps and around fasteners. Torch-on membrane is generally not appropriate on sheeting.
How long does a metal roof coating last?
Usually 5 to 10 years depending on the system, the preparation and exposure. Coastal roofs sit at the lower end because salt keeps working on the substrate under the coating.
Why is my metal roof noisy and dripping inside?
Dripping without rain is usually condensation on the cold underside of the sheeting rather than a leak. That is a ventilation and insulation problem, and coating the top surface will not change it.
Should the roof be painted or waterproofed?
They overlap. A protective coating on a sound sheet roof is closer to roof painting. Where laps and fasteners are being sealed and reinforced, it is waterproofing. Most jobs on older sheet roofs involve both.
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