Install, inspect and maintain

A drainage design is only as good as the gutters that are actually hung and the outlets that are actually clear. Installation turns numbers on a drawing into falls of a few millimetres over several metres, front edges set a little lower than backs, expansion gaps set for the day’s temperature and outlets fitted the right way up. Maintenance keeps those outlets open for decades. Both are routinely done by eye, and both decide whether the calculations in the earlier chapters mean anything.

This chapter covers setting out and installing W-40’s gutters, the checks before handover, the water test, safe access for the people who will maintain them, an inspection and cleaning schedule, the records that keep the design alive, and what to do when the roof changes. The failure case is a blocked rainhead that went unnoticed for a season after a change of maintenance contractor, until the overflow designed in Chapter 6 did its job.

Set out the falls

Falls of 1:500 and 1:200 are too small to set by eye. Over the roughly 3.3 m from each high point to each outlet on W-40’s rear gutter, a 1:500 fall is only about 6.7 mm. Over each 20 m run of the box gutter, 1:200 is 100 mm.

The roof plumber sets a laser level, or a tight string line, along the line of the gutter, marks the height of the high point and of each outlet, and sets every bracket between them by measurement from the line. For the eaves gutter, a simple table of bracket heights, from the line, at each bracket position, removes guesswork. For the box gutter, the continuous support is set to the fall before the gutter is laid, then checked again with the level once the gutter is in place.

At the same time, each eaves gutter bracket is set so that the front edge sits 15 mm below the back, as Chapter 3 required. A small spirit level across the gutter, at every bracket, confirms it.

Install with the details right

The details that matter most are the ones that are hard to see from the ground once the work is finished.

Figure 1Installation checks before W-40's drainage is handed over

• Do: Falls measured at every bracket and outlet, matching the design table1:500 eaves, 1:200 box gutter
• Do: Front edge 15 mm below the back at every bracketchecked with a level across the gutter
• Do: Brackets at the maker's spacing, with fixed and sliding points as designedone fixed point per run
• Do: Laps in the direction of flow, riveted and sealedwater runs over each lap, not into it
• Do: Expansion joints at the high points, gap set for the metal temperature on the day30 mm at 25 °C in the box gutter
• Do: Outlets flared, with domed strainers, sealed into the guttersix rear, two rainhead outlets
• Do: All swarf and offcuts removed from gutters and roofmetal filings rust and stain coated steel
• Do: Overflow paths clear and as drawnfront edges, rainhead lips, parapet overflows
• Avoid: Sealant used to fill gaps the metalwork should closesealant is not a substitute for a proper lap

Swarf, the fine metal filings from drilling and cutting, deserves its own mention. Left on coated steel, each filing rusts within days and leaves a stain, and in a gutter that holds a little water, a scatter of swarf can start corrosion of the coating itself. Roof plumbers sweep or blow it off at the end of each day.

Water-test before handover

At completion, every gutter is tested with water before the building is handed over. W-40’s roof plumber ran a hose into the high point of each gutter section in turn and watched three things: that water ran freely to the outlet along the whole run, that no water dripped from any lap or joint, and that nothing remained standing in the gutter a few minutes after the hose was turned off. Standing water means a sag or a wrong fall, and it is far cheaper to fix the day the scaffold is still up.

The overflow tests described in Chapter 6 were done at the same time: a plugged outlet, a plugged rainhead downpipe and a blocked box gutter opening, each showing the water leaving by its designed path. The results, with photographs, went into the handover file.

Plan safe access for maintenance

Gutters must be maintained for the life of the building, which means people will work at height on and near the roof many times. Safe Work Australia’s model Code of Practice for managing the risk of falls at workplaces sets out how to manage that risk, starting with eliminating work at height where possible, then using passive protection such as guardrails and walkways, then systems such as fall restraint or arrest, with ladders and administrative controls as the least effective options.

W-40’s design applied that thinking from the start. The rear eaves gutter is low enough to be cleaned from a mobile elevating work platform from the ground. The front box gutter is reached through a roof hatch with a fixed ladder, along a walkway beside the parapet, with guardrails where the parapet is too low to act as edge protection. Anchor points for fall restraint are fixed along the ridge. The roof sheets themselves are not walked on, and the plant platform proposed for later will have its own access. Designing access in is cheap; adding it after a fall is not.

Inspect and clean on a schedule

Inspection frequency depends on what falls on the roof. W-40 has a row of eucalypts along its rear boundary, which shed leaves and bark year-round and heavily in summer.

Figure 2W-40's roof drainage maintenance schedule

1. Every monthFrom the groundlook for overflow stains, sagging gutters and debris at outlets; check rainhead fronts
2. Before storm seasonOn the roofclean all gutters, the box gutter, rainheads and strainers; check falls and joints
3. After leaf dropOn the roofclean gutters and outlets under the boundary trees
4. After any severe storm or hailOn the roofcheck for hail or debris in the box gutter and at every outlet
5. Every yearDesigner or senior roof plumberreview records, check sealant, expansion joints and coating condition

Cleaning means removing debris from the gutter, not washing it down the downpipes, where it can lodge in an offset or a stormwater pit. Debris is bagged and taken off the roof. Strainers are lifted and cleaned. After cleaning, a bucket of water poured at each high point confirms the outlets run freely.

Gutter guards: help or hindrance

Gutter guards, meshes or perforated covers over the gutter, are sold as a way to avoid cleaning. They help where leaves are the main problem: W-40’s owner fitted a guard to the rear gutter under the eucalypts after the first year’s records showed how often it filled. They do not remove the need for maintenance. Leaves and bark collect on top of the guard and must still be brushed off; fine debris and seed pods pass through and settle in the gutter; and a guard can trap hail or leaves over an outlet.

Two rules made the guard work at W-40. It was chosen to sit clear of the gutter’s front edge, so that it could not interfere with the overflow, which Chapter 6 showed is the commonest way guards cause damage. And the inspection schedule kept the rear gutter on a regular cycle, with the guard lifted at each annual inspection so the gutter beneath could be checked.

Figure 3Ways to clean W-40's gutters

	Rear eaves gutter	Front box gutter and rainheads
Access	mobile elevating work platform from the ground	roof hatch, fixed ladder and guarded walkway
Cleaning	hand and scoop, debris bagged; gutter vacuum from the platform	hand and scoop in the gutter, debris bagged and lowered
Strainers and outlets	lifted, cleaned and refitted	rainhead outlets cleaned from the walkway side
Check after cleaning	bucket of water at each high point	bucket at the high point and each end
Main hazard controlled	working at the roof edge	working beside the parapet and near skylights

Look after the coating

Metallic-coated and prepainted steel gutters last as long as their coatings. The coating is damaged by things that sit wet against it: leaves, silt, ponded water and swarf. It is also damaged by abrasive cleaning with wire brushes or by walking in the gutter in boots that carry grit. The annual inspection looks for early signs, such as white or red corrosion products, blistering paint or bare edges at cuts, and records them so their progress can be followed. A small area treated early with the coating maker’s recommended touch-up system costs little; a corroded gutter replaced early costs a great deal. When the time comes to replace a gutter, the design note tells the replacement installer what the original was meant to carry, so the new gutter is at least as good as the old.

Keep records

Every inspection and clean is recorded: the date, who did it, what was found, what was done, and photographs of anything unusual. W-40’s records sit with the design note from Chapter 1 and the handover file, so that anyone working on the roof can see what the drainage was designed for, how it was tested and what has happened since.

The records also earn their keep. After a year, they showed that the gutter under the eucalypts needed cleaning twice as often as the rest, and that the box gutter rarely held more than a handful of leaves. The schedule was adjusted accordingly, with more attention where it was needed and less where it was not.

Hand over knowledge, not just a roof

At handover, W-40’s designer walked the site with the owner’s facilities manager and the first maintenance contractor. Together they looked at every outlet, every overflow and the expansion joints, from the ground and from the roof walkway. The designer explained what each overflow was for and what it meant if it ran, why the gutter fronts sat lower than their backs, why the expansion joints must never be sealed solid, and why nothing made of copper or lead should ever be installed upstream of a gutter. The handover file held the design note, the as-installed drawings, the water-test photographs, the maintenance schedule and the makers’ instructions for the gutters, outlets and coatings. An hour on the roof at handover is the cheapest way to keep a drainage design working long after its designer has moved on to other projects.

When the roof changes

Roofs change. A plant platform is added, a skylight is cut in, a neighbour builds a higher wall alongside, an extension is joined on. Each change can alter a catchment, add concentrated flow or block an overflow path. W-40’s design note records a simple rule: any change to the roof or anything draining onto it triggers a review of the affected catchments, outlets and overflows, using the methods in Chapters 2 to 6, before the change is built. The proposed plant platform, flagged in Chapter 2, will be the first test of that rule, and its review is already listed in the maintenance plan.

A failure case: the season without inspections

This is an illustration. Two years after W-40 was completed, the owner changed maintenance contractors. The new contractor’s schedule, copied from a different building, listed gutter cleaning once a year, and nobody compared it with W-40’s records, which showed more frequent cleaning was needed.

During the following summer, a tennis ball from the park across the street lodged in the eastern rainhead’s outlet, and leaves built up behind it. The downpipe was blocked for weeks without anyone noticing, because in light rain the rainhead simply filled and drained slowly.

Then a heavy storm arrived. The rainhead filled and spilled over its front lip onto the street paving, exactly as Chapter 6 designed. A staff member who had been shown the overflows at handover saw water pouring from the rainhead front and reported it the same afternoon. The inspection found the blocked outlet, with the box gutter’s water still draining freely into the rainhead and well below its roof-side edge. No water had entered the building.

The detection came from the visible overflow and a staff member who knew what it meant. The correction was to clear the outlet and to restore the inspection schedule from W-40’s records, with a note in the maintenance contract that the schedule is set by the building’s records, not by a standard template. The design had protected the building; the records and the trained eye had made sure the warning was heard.

How this applies to a small Australian business

Install gutters to measured falls, with front edges lower than backs and expansion gaps set for the day’s temperature, and remove swarf before it stains. Water-test every gutter and every overflow before handover, and photograph the results. Design safe access for maintenance into the building, following the falls code’s order of controls. Inspect and clean on a schedule set by your site’s trees and storms, keep records, and adjust the schedule from them. Show staff the overflows and tell them what to do when they run. And recalculate whenever the roof or anything draining onto it changes.

Exercise: reading a fall survey

A roof plumber surveys one rear gutter run, from its outlet to the next high point, about 3.33 m away. Heights of the gutter sole above the outlet, in millimetres, measured at 0, 0.8, 1.6, 2.4 and 3.33 m from the outlet, are 0, 1.0, 3.5, 3.0 and 6.5. What drop does a 1:500 fall require over the run? Does the run meet it overall? Does any part of the run hold water, and what should be done?

Worked answer. A 1:500 fall over 3.33 m requires a drop of about 3,330 ÷ 500 ≈ 6.7 mm. The run drops 6.5 mm overall, very slightly less, which on its own would be acceptable to correct at the next adjustment. But between 1.6 m and 2.4 m the sole rises from 3.0 mm to 3.5 mm as water travels towards the outlet: water flowing from the high point reaches 2.4 m at 3.0 mm, then must climb to 3.5 mm at 1.6 m. That section holds a shallow pond about 0.5 mm deep, with a sag centred near 2.4 m. The bracket or brackets around 2.4 m should be raised to restore a continuous fall, and the whole run reset to give the full 6.7 mm, then water-tested again.