Skip the Kettle Trips
Boiling water works on small patches, but for anything bigger than a doorstep, there’s a much easier way. One application covers your whole patio and keeps working for months.
It sounds almost too simple. Boil the kettle, pour it on the moss, job done. No chemicals, no expense, just water you’ve made really hot.
But does it actually work? The answer is yes, sort of, with some significant caveats. Let’s look at when boiling water is worth trying and when you’re better off with something else.
The Short Answer: Yes, But…
Boiling water will kill moss. The heat destroys the plant cells on contact, and you’ll see the moss turn brown within hours of treatment. It’s a genuine, chemical-free way to kill moss.
However, there are several reasons why it’s not the miracle solution it might seem:
It only kills what it touches. Boiling water has no residual effect. The moment it cools (which happens in seconds), it stops working. Any moss that didn’t get directly scalded will survive, and new moss spores landing on the surface tomorrow will grow just as happily as before.
The heat dissipates quickly. By the time boiling water has run a few inches across a paving slab, it’s no longer boiling. It might still be hot, but not hot enough to kill moss effectively. You need direct contact with properly boiling water.
It does nothing to prevent regrowth. Unlike proper moss treatments that continue working for weeks or months, boiling water offers zero ongoing protection. Moss will return just as quickly as it did before, often within weeks.
The Practicality Problem
Here’s where the boiling water method really falls down: scale.
A standard kettle holds about 1.7 litres. That’s enough to treat perhaps one or two paving slabs if you’re thorough. An average patio might have 30 to 50 slabs. That’s a lot of kettle trips.
Let’s do the maths. If your patio has 40 slabs and each needs two kettle loads to cover properly, that’s 80 kettle boils. At 3 minutes per boil plus walking time, you’re looking at 4 to 5 hours of kettle shuttling. And by the time you’ve finished the last slab, the first ones are already cooling.
Then there’s the safety aspect. Carrying boiling water across the garden repeatedly isn’t without risk. Trips, spills, and splashes happen, and boiling water causes serious burns. It’s not a job for anyone with mobility issues or when children or pets are around.
For a single mossy step or a small patch between slabs, boiling water is fine. For anything larger, it becomes impractical very quickly.
When Boiling Water Makes Sense
Despite its limitations, there are situations where boiling water is a reasonable choice:
Small problem areas like a single doorstep, the gaps between a few slabs, or moss growing in a crack. For these, a couple of kettle loads is manageable.
When you want to avoid chemicals entirely. If you’re treating an area where food is grown, where pets lie, or where you simply prefer not to use any products, boiling water is genuinely chemical-free.
As an immediate fix before guests arrive. Boiling water works instantly. If you’ve got visitors in an hour and a mossy patch you’d forgotten about, a kettle of boiling water will kill it on the spot (though you’ll still need to brush off the dead moss).
For weeds in paving gaps as well as moss. Boiling water kills most small plants, so it’s useful for the random weeds that pop up between slabs too.
How to Use Boiling Water Effectively
If you’re going to try it, here’s how to get the best results:
Boil the kettle and go immediately. Every second of delay means cooler water. Don’t answer the phone, don’t get distracted. Straight from kettle to moss.
Pour slowly and directly onto the moss. Don’t just splash it in the general direction. Get close and pour steadily so the water soaks into the moss rather than running off.
Do multiple passes for thick moss. If the moss is really established, one kettle load probably won’t penetrate to the base. Let the first load soak in, then do a second pass.
Brush off the dead moss after a day or two. The moss won’t disappear on its own. Once it’s brown and dead, sweep or brush it away to prevent it becoming a mat that holds moisture for new growth.
What About Boiling Water Plus Salt?
You’ll sometimes see advice to add salt to boiling water for extra moss-killing power. Salt does kill moss, but mixing it with boiling water is overkill and potentially problematic.
Salt can damage plants, contaminate soil, and corrode certain surfaces. It can also leave white residue on paving. If you want to use salt as a moss treatment, it’s better used separately and targeted carefully. Don’t just tip salty boiling water everywhere.
The Regrowth Problem
Here’s the real issue with boiling water as a moss treatment: it does nothing to address why moss is growing there in the first place.
If your patio is shaded, damp, and in the UK (where moss basically has ideal conditions year-round), new moss will establish itself within weeks of treatment. You’ll be back with the kettle before long.
Moss spreads through microscopic spores that are literally everywhere. The moment conditions are right, new growth begins. Boiling water kills existing moss but does nothing to create a hostile environment for new spores.
This is where proper moss treatments have the advantage. A good moss killer doesn’t just kill existing growth. It leaves an active residue that continues to prevent new moss from establishing for weeks or even months. One application does what dozens of kettle trips cannot.
The Better Alternative
For anything beyond a tiny patch, a dedicated moss treatment is simply more practical.
A pump sprayer covers a full patio in minutes rather than hours. The treatment penetrates moss effectively, killing it right through to the base. And most importantly, it keeps working after application, preventing regrowth rather than just killing what’s already there.
It’s not that boiling water doesn’t work. It does. It’s just inefficient and offers no lasting benefit. You’re essentially treating the symptom without addressing the problem.
Our guide to tackling moss, mould and algae covers treatment options in more detail, including how to prevent regrowth long-term.
Comparing DIY Methods
If you’re determined to use household methods rather than dedicated treatments, here’s how boiling water stacks up against the other common options:
Vinegar works but takes longer to see results. It has some residual effect but can damage plants and isn’t great for all surfaces.
Bleach is effective but harsh. It can discolour surfaces, kill nearby plants, and isn’t environmentally friendly.
Washing up liquid is very weak. It might help shift surface algae but won’t kill established moss.
Boiling water is immediate and genuinely chemical-free, but offers no prevention and is impractical for larger areas.
None of these match a proper moss treatment for effectiveness and convenience, but if you’re going chemical-free on a small area, boiling water is one of the better options.
Tired of endless kettle trips? One spray covers your whole patio and keeps moss away for months. Our Moss, Mould & Algae Killer works while you put your feet up.
