A roof goes up quickly and then disappears behind a ceiling for thirty years. Almost everything that determines whether it performs happens in the few days when you can still see it.
From Trusses Up: A New Roof Install — practical guidance from the team running roof installation on the Garden Route. Below is the sequence a new roof actually follows, what to look at at each stage while it is still visible, and the four things that go wrong most often on Garden Route roofs.
Before anything arrives: design and setting out
Trusses are an engineered product. They are designed by the manufacturer’s software for your specific roof — the span, the pitch, the covering weight, the wind zone and any point loads — and they arrive as a set that only fits that roof.
The design has to know about the covering before manufacture. A tile roof and a sheeted roof are very different dead loads, and a truss designed for one is not automatically adequate for the other. Changing the covering after the trusses are ordered is not a finish decision; it is a structural one.
Point loads have to be declared up front too. A geyser in the roof space, a water tank, a solar PV array, air conditioning plant. Each is a concentrated load the design either allowed for or did not, and adding one afterwards to a roof that did not allow for it is one of the more common ways a sound structure gets quietly overloaded.
The wall plate is the foundation of the roof. Level, straight, continuous and — critically — properly anchored down into the wall. Everything above it depends on it, and a wall plate that is out of level puts every truss out with it.
Setting out establishes the truss spacing and the position of the first and last truss. Get this wrong and the covering does not land on battens where it should, which turns into a fiddle at every course.
On the covering, the main South African sheeting supply comes through Safintra, Global Roofing Solutions and the ArcelorMittal-fed rollformers, with Chromadek the pre-painted product most people recognise by name and Zincalume or Colorbond specified where the coating mass needs to be heavier. Tile comes largely through Coverland, Marley and Monier. Merchant supply on the Garden Route runs through the usual houses — Builders, BUCO, Cashbuild and the timber merchants — but sheeting is normally ordered cut to length for the specific roof rather than bought off a rack, which is why the measure has to be right before anything is ordered.
Delivery, handling and erection
Trusses are strong in their own plane and remarkably weak out of it, which governs how they are handled.
Damage on delivery is a real risk and it is worth looking for. Trusses lifted at the wrong points, dragged, or stacked badly can have nail plates knocked partly out of the timber. A plate that is not fully seated is not the joint the engineer designed, and it is easy to miss once the roof is up. Damaged trusses get repaired to the manufacturer’s instruction or replaced — not nailed back and forgotten.
Storage on site should be off the ground, supported at the correct points, and protected. Timber sitting flat in a Garden Route winter takes up moisture, and wet timber moves when it dries.
Erection is plumb, at the correct spacing, on the wall plate, temporarily braced as it goes. A row of erected but unbraced trusses is genuinely unstable — the classic construction failure is a row going over like dominoes because temporary bracing was skipped for an hour.
Fixing to the wall plate is where the roof resists wind uplift. On the Garden Route that matters more than in most of the country: the southeaster does not just push a roof sideways, it lifts it. Hoop iron, straps or proprietary tie-downs, correctly fixed and correctly spaced, are what holds it, and they need to be visible and countable before the ceiling goes on.
Overhangs and the eaves detail get set here too — the line the fascia will follow, and the ventilation path into the roof space.
Bracing — the part that gets skipped
If you look at only one thing while your roof is open, look at the bracing.
A truss is a two-dimensional frame. A row of them is a row of two-dimensional frames. What turns that into a stable three-dimensional structure is the bracing that ties them to each other and to the building below.
Diagonal bracing in the plane of the rafters stops the whole row racking. Longitudinal bracing along the length holds the spacing and prevents the trusses buckling sideways under load. Web bracing restrains individual members where the design requires it. Tie-downs connect the whole assembly to the walls.
The bracing layout comes from the truss design, and it is specific — it is not a generic pattern a carpenter applies from experience. It should be on the drawing and it should be on the roof.
It is also the most commonly omitted element in South African roofing, and the most commonly removed afterwards. Someone needs to get a water tank into the roof space and a brace is in the way, so it gets cut. Nothing happens for years, and then a big front comes through.
Count it before the ceiling goes up. Once the ceiling is on, verifying bracing means a torch, a hatch and a lot of crawling. Before the ceiling, it is a two-minute look.
Battens, underlay and covering
Underlay first, and it matters more than people think. On a tiled roof the underlay is the actual waterproofing layer — the tiles shed the bulk of the water and the underlay catches whatever gets past, then drains it out at the eaves. It has to run continuously, lap correctly down the slope, and — the detail most often got wrong — discharge into the gutter rather than behind it. An underlay that stops short of the gutter delivers water straight into the fascia and the rafter ends.
On a sheeted roof the underlay is doing a slightly different job: managing condensation as much as incidental water. In a humid coastal climate, a sheeted roof over an unventilated space without an underlay will drip on the ceiling and everybody will call it a leak.
Battens or purlins at the centres the covering requires, fixed into the truss members rather than wherever is convenient, and set out from the eaves so the courses land correctly and the last course is not a sliver.
The covering, fixed to the manufacturer’s specification for the exposure — the right fixing type, the right centres, and closer fixing at the edges and corners where wind uplift concentrates. This is not the same everywhere on the roof, and a uniform fixing pattern across a coastal roof is under-fixed at the perimeter.
Cutting matters on sheeting. Angle grinders heat-damage the coating at the cut edge and throw hot swarf across the roof, which rusts in place. Nibblers or shears, and a clean-down at the end of each day.
Flashings, rainwater goods and the details
The covering rarely leaks. The junctions do, and this is where an experienced roofer earns the difference.
Ridge and hip. Bedded in mortar, or a mechanically fixed dry ridge system. Dry systems avoid the classic failure — mortar bedding that cracks and lifts over time — and are worth considering on exposed roofs.
Valleys. Sized for the catchment, lapped in the right direction, and with the tiles or sheets cut back far enough that the channel is not obstructed. Valleys carry concentrated flow and they overtop when they are tight.
Abutments. Where the roof meets a wall, a chimney or a parapet. Formed metal flashing, dressed into a chase or under a cover flashing. A mortar fillet is a rigid material bridging a joint between two things that move differently, and it always cracks eventually.
Penetrations. Proprietary flashing units for pipes and flues, and properly detailed brackets for solar mountings. Retrofitted solar is one of the more common causes of new leaks on previously sound roofs.
Gutters, fascia and downpipes. Sized for the roof area and the rainfall, laid to a consistent fall, on brackets at adequate centres fixed into sound timber, discharging somewhere that takes the water away from the building.
Metal specification on the coast. Every metal component — flashings, valley linings, clips, nails, brackets — corrodes faster in salt air and frequently fails while the covering is still sound. Specifying the right metal for the exposure is one of the cheapest decisions on the roof and one of the most consequential.
Handover, and what you should be given
A completed roof produces paperwork, and you want it in hand rather than promised.
The A19 certificate. Certification by a competent person that the erected roof structure matches the engineered design and is correctly braced and fixed. It certifies what is standing on your building, which is different from the truss manufacturer’s design certificate. Banks, insurers and conveyancers all ask for it eventually, and obtaining it after the ceilings are up is considerably harder.
The truss design drawings, including the bracing layout. Keep them — they are what an engineer will want if you ever add a load or alter anything.
The covering manufacturer’s warranty documentation, which is conditional on installation to their specification. A roof installed outside spec can look identical and carry no material warranty at all.
Our written workmanship guarantee.
And a short maintenance note. On the Garden Route that is not a formality: clear the gutters and valleys ahead of the wet season, check the flashings after a big front, replace perished washers as a batch rather than one at a time, and have the roof looked at annually. That routine is what gets a roof to its design life, and skipping it is what makes an eight-year-old roof look like a fifteen-year-old one.
Frequently asked questions
How long does it take to install a roof?
On a normal residential footprint the structure and covering is typically a matter of days to a couple of weeks, depending on complexity, access and weather. The bigger programme point is not the duration but the timing — getting a building weathertight before the wet part of the year is the single most valuable scheduling decision on a Garden Route build, and it is worth reorganising a start date for.
What is roof bracing and why does it matter?
A truss is a flat frame, strong in its own plane and almost unstable out of it. Bracing — diagonal bracing in the plane of the rafters, longitudinal bracing along the length, web bracing where required, and tie-downs to the walls — is what turns a row of flat frames into a stable three-dimensional structure that resists wind. The layout comes from the truss design and is specific to it. It is the most commonly omitted element in South African roofing and the most commonly cut afterwards to get something into the roof space.
Do I need an underlay under roof tiles?
Yes. On a pitched tiled roof the underlay is the actual waterproofing layer — the tiles shed most of the water and the underlay catches wind-driven rain, water backing up behind a blocked valley, and run-off from any cracked tile, then drains it out at the eaves. It has to lap correctly and discharge into the gutter rather than behind it. When an older tiled roof starts leaking in several places at once, a perished underlay is almost always the reason.
What is an A19 certificate and who issues it?
It is the certification of the erected roof structure by a competent person — confirming that the trusses as built match the engineered design and are correctly braced and fixed. It is separate from the truss manufacturer’s design certificate, because it certifies the thing actually standing on your building. Get it at handover; banks, insurers and conveyancers all ask for it, and reconstructing it once the ceilings are closed is expensive.
Can I add a geyser or solar panels to my roof afterwards?
Only after an engineer has checked it. Both are point loads, and the truss design either allowed for them or it did not. Adding one to a roof that did not is a common way a sound structure gets quietly overloaded. Solar also puts fixings through the covering, which is a frequent source of new leaks on previously sound roofs — the mounting needs a proper flashing detail, not a bead of sealant.
What happens if trusses are damaged in delivery?
They get repaired to the manufacturer’s written instruction, or replaced. What must not happen is a knocked-out nail plate being tapped back and forgotten — the plates are engineered connections, and a plate that is not fully seated is not the joint that was designed. Inspect trusses on delivery and again before the ceiling goes on, because after that you need a torch and a hatch to see anything.
Why is fixing different at the edges of a roof?
Because wind uplift is not uniform. Perimeter and corner zones experience substantially higher uplift pressures than the field of the roof, so the fixing pattern is tightened there. A uniform fixing pattern across a coastal roof is adequate in the middle and under-fixed exactly where the wind works hardest — which is why sheets lift at edges and corners rather than in the centre.
Related reading
- Roof truss types, explained
- How a roof gets installed
- Installing a roof, section by section
- Coastal corrosion on SA roofs
- Roof installation in George
Putting a roof on?
We build to the engineered design, brace it properly, tie it down for coastal wind, and hand over the A19 with the rest of the paperwork. Come and look at it before the ceiling goes on — we would rather you did.
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