Dark streaks make many homeowners think the roof is finished, but streaks and a worn-out roof are different problems with very different price tags. The comparison below shows what soft washing and replacement each fix, the cost logic behind the choice and a short path for deciding.
In This Article
The comparison in one table
| Factor | Roof soft washing | Roof replacement |
|---|---|---|
| What it fixes | Algae streaks, moss and lichen on shingles that are still sound | Worn, cracked, curled or leaking shingles and a failing roof |
| What it cannot fix | Lost granules, curling, leaks and age | Underlying structure, ventilation or drainage problems, unless they are dealt with at the same time |
| Cost scale | A service visit, quoted after assessment | A major renovation, running to thousands of dollars for most homes |
| Disruption | Usually one visit | Several days, with noise, debris and weather planning |
| Effect on lifespan | Removes growth that holds moisture, but adds no years to worn shingles | Starts a new clock |
| Warranty angle | Check your shingle maker's cleaning guidance first | New shingles carry the maker's own terms |
D&D does not publish a starting price for roof cleaning, because pitch, size, access and the amount of growth all change the job. It is quoted in writing after assessment.
When cleaning is the right call
A soft wash makes sense when the problem is growth on a roof that is otherwise doing its job. Look for these signs from the ground:
- Streaks or patches, but shingles that lie flat and look whole.
- Granules still covering the surface, with no bare black patches.
- No stains on the ceilings below and no known leaks.
- Moss or lichen that has not yet lifted the shingle edges.
Replacing a sound roof for looks alone spends a large sum to solve a small problem. The stains are usually the cheapest thing on the roof to fix.
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When cleaning will not help
Some signs say the roof has aged out, and cleaning would only tidy up something that is about to be replaced.
- Bare patches where granules have worn away, or a gritty layer of granules in the eavestrough.
- Curling, cupping or cracked shingles, and tabs that lift in the wind.
- Water stains on ceilings, or daylight and damp insulation in the attic.
- A sagging roof deck or soft spots when you look along the slope.
- Moss thick enough to have lifted or broken shingles.
If two or three of these apply, book a roofer's condition opinion before spending on cleaning. Washing a roof that needs replacing puts the money in the wrong place.
Useful questions for the roofer: how many years does this roof likely have left, would repairs stretch that, and is cleaning worth doing now or should the money go towards replacement? Ask for the answers in writing so you can compare them with a cleaning quote.
The cost logic most people miss
- Cleaning a sound roof is cheap insurance. Moss and lichen hold water against shingles and can lift their edges. Removing them is maintenance that lets a roof reach its expected life.
- Cleaning a failing roof is wasted money. A tidy roof that leaks is still a leaking roof, so assess first and clean second.
- Stains are cosmetic, condition is not. A buyer's inspector reads the roof's condition, but stains still make a house look neglected, so cleaning helps presentation when the roof is sound.
- Replacing anyway? Plan ahead. Ask about algae-resistant shingles, which include copper-containing granules, so you are not cleaning the new roof in a few years.
A three-step decision path
- Look. Use binoculars from the ground on every slope. Check the eavestroughs for granule grit and the ceilings and attic for stains.
- Ask. Get a roofer's opinion on the roof's condition and remaining life, and request it in writing if the roof looks tired.
- Decide. A sound roof with growth gets cleaned. A tired roof with a few problem spots may need repairs first. A failing roof gets replaced, and cleaning waits.
If you are still unsure, the guides to soft washing a roof and moss and lichen removal from roofs explain the method and its limits.
Safety and who does the work
Roof work is the riskiest part of exterior cleaning. Wet algae is slippery, and a fall is serious. Do not pressure wash shingles, either. High pressure strips granules, and most shingle makers advise against it.
On roofs, the Working at Heights certification held by D&D's crew members matters most, and roof cleaning is quoted free after assessment, with the price confirmed in writing before work begins. For a wider look at the options, see roof cleaning cost in Ontario.
Key Takeaways
- Streaks, moss and lichen on sound shingles are a cleaning job, while worn granules, curling, leaks and age are replacement questions.
- Cleaning is a service visit and replacement is a major renovation, so replacing a sound roof for looks alone spends a lot to solve a small problem.
- Assess the roof's condition before cleaning, since a tidy roof that leaks is still a leaking roof.
- Never pressure wash shingles, and choose algae-resistant shingles if you are replacing anyway.
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