Roof cleaning (tiles)

[Grumps]

One of my neighbours has just had his tiled roof cleaned (pressure washer). Whilst it does look cleaner (not really that bad to begin with), they've obviously not noticed the muddy stains/dribbles on his fascias and white walls. I suspect they'll be back to tidy up. But, what are the benefits of having this done? Googling just shows adverts from every man and his dog that has a pressure washer. Also, is pressure washing directed under the tiles (that is up the slope of the roof) bad?

[Harry Bloomfield Esq]

Benefits are nil, with the potential for considerable damage.

Just imagine where all that water directed up tiles will end up - inside your loft, soaking any loft insulation, soaking the ceiling plaster.

[Jim Stewart ...]

no sarking then ?

[Colin Bignell]

It looks prettier?

[alan_m]

More risks than benefits with higher pressure washing.

Probably better to very low pressure spray with Benzalkonium Chloride, thoroughly soaking the tiles and let time and the weather finish the job. I did this to one side of my roof that had low/moderate amounts of moss and surface lichen. Six months later the roof is free of moss and just small amounts of white lichen (although some of that may pigeon shit). The tiles are now a similar shade of grey as when they were first fitted.

I live in the very dry SE of Essex where we don't have rain for months on end to wash off the the dead moss and lichen.

I was worried that the moss in the cracks between the concrete tiles would retain water and freeze during the winter months thus destroying the edge of the tiles.

[Andrew]

Which includes having lead flashing removed and replaced by bits of 'flashband', as happened to an elderly neighbour a few years ago.

[pinnerite]

Before buying my bungalow, I had it surveyed. The surveyor recommended that the roof be cleared of 50 years of moss.

When the crew came to do it they offered me the choice of a pressure wash or a manual scrape.

They did a good job. My meticulous neighbour saw the result and took their number.

Regards, Alan

[NY]

We had the tiles of our house pressure-washed, as an extra job after they'd repaired some missing tiles that had come off in a gale. The noise of the pressure washer on the tiles reverberated through the whole house for the many hours it took them to do the job. What a din! The guy tried to sell me a coating that could be applied to the tiles afterwards to prevent them getting dirty/mossy in the future, and by the time I'd checked with my wife who was at work and reported "no" to the roofer (which only took about half an hour), he'd already ordered the stuff and was not best pleased that we decided not to have it done. He was a typical pushy salesman who doesn't take "no" for an answer, assumes "yes", and then gets miffed when the customer decides "no" ;-(

[alan_m]

If already on the roof, £25 of chemicals (at today's prices) plus around

30 minutes labour to apply.

[AnthonyL]

What type of tiles?

Around here the tiles are concrete and properties that have had their roofs pressure washed have nice looking roofs for about 2 years.

I've spoken to two roofers who say that pressure washing is a bad idea as it destroys the protective layer that builds up.

They (both reputable roofing/building companies) said that moss etc is best removed with a stiff brush and definitely no scraping.

[Brian Gaff]

Depends what is behind the tiles, nothing behind mine so very bad if I did it!

Brian

[Brian D]

Neighbours had roof pressure washed and sealed. In the following year many attempts to repair damage.

Ended up with a new roof (by a different roofer).

[Andrew]

Who could have been working hand in glove with the original guys.

Trust no-one where roofing is concerned.