Moss and maintenance
Moss, and keeping a roof off the replacement list
Nanaimo Roofers removes moss and maintains asphalt and metal roofs across Nanaimo, Cedar and Lantzville. Roofs here take 1,000 mm of rain a year under heavy tree cover, and RCABC sets the inspection interval at twice a year, in spring and in fall.
Moss is not a cosmetic problem. It is a wick, and it works uphill.
What moss actually does
A moss mat holds water against the shingle instead of letting it run off, and as it thickens at a course edge it lifts the tab above it. Once a tab is lifted, wind-driven rain gets under the course and reaches the underlay. On a north face under fir cover that process can take a decade off a roof rated for twenty-five to thirty years.
How it comes off
Treatment first, then a gentle removal working down the slope so nothing is driven under a course. Asphalt shingles are never pressure-washed: the granules are the wear surface and pressure strips them, which trades a moss problem for a shorter roof. Metal panels tolerate more, but the fasteners and gaskets on a profiled roof do not.
Keeping it off
A strip of zinc or copper at the ridge releases enough metal in runoff to slow regrowth down the slope below it. Branches overhanging the roof get cut back so the surface dries between rains, and gutters and valleys get cleared so debris does not hold moisture at the edge. RCABC puts it plainly: keeping a roof free of debris and vegetation is part of maintaining it.
Why spring and fall
RCABC sets regular inspection by competent personnel at least twice a year, in the spring and the fall. The spring inspection shows what winter did and allows repairs in the best possible weather. The fall inspection is what gets the roof ready for the winter coming. A roof looked at on that schedule tends to need repairs rather than replacement.
Metal roofs are not exempt
Moss will not root in a standing seam panel, but it will sit in a valley, pack behind a snow guard and block a downspout. The maintenance visit on a metal roof is about drainage, fasteners and sealant at penetrations rather than the field of the roof itself.
What's included
Roof moss treatment and removal
Zinc and copper ridge strip installation
Gutter, valley and debris clearing
Spring and fall roof inspection
People also ask
Can moss just be scraped off?
Dry scraping takes granules with it and pulls at the tab edges it is meant to free. Treating first and removing gently afterwards leaves the wear surface where it belongs.
Does a moss-covered roof always need replacing?
Not on its own. What decides it is what is underneath: whether the tabs have been lifted long enough for water to reach the underlay, and whether the deck has gone soft anywhere.
How long do ridge strips last?
A strip works by shedding metal into the runoff, so it is consumed slowly and its effect reaches only the slope below it. A roof with dormers or several planes needs more than one run.
Should gutters be done at the same time?
It is the same access and the same debris. Clearing gutters and valleys in the same visit is what stops water backing up at the eave, which is where the damage ends up.
Keep exploring
- What a new roof costsInstalled price by material, and what moves it on a given roof.
- Permits by communityWho issues the permit for an address, and what each authority asks for.
- Where the work isThe communities covered across the Regional District of Nanaimo.
- Roof repair and leak tracingFlashing, valleys, penetrations and laps. Finding where water enters a roof, which is almost never directly above the stain on the ceiling.
- Metal roof systemsStanding seam and profiled metal from a slope of 1 in 4 with no upper limit, detailed for a 2.1 kPa ground snow load and a 0.50 kPa design wind.
- Nanaimo Roofers home