Cleaning the tiles on a roof

[Speicher]

An cold-caller type person knocked on my door this morning, asking me if I wanted to have the tiles on my roof cleaned.

He said that the algae that builds up will damage the roof, or words to that effect. Being polite, I responded that I did not think algae damaged tiles. He then asked me if I had seen the roof of the house three doors down.

Well yes, I have, surprisingly enough. They cleaned it. But now instead of being dark red tiles, they look a lot paler. This looks to me like they have been abraided/scratched/scuffed/damaged. I thought the algae was from bird droppings when they (the birds) perch on the tv aerial.
Is the cleaning process causing more harm than good?

I am concerned that elderly people living on their own would be bamboozled into having "work" done, that in addition to not being necessary, is possibly detrimental to the tiles.

Your technical advice on this would be appreciated.

 

[LordoftheTeapot]

I would sugest a phone call to your local trading standards (Council) is in order. May be a con

 

[ianrauk]

I would say if you have no leaks and the tiles are in good shape I wouldnt bother.

 

[4F]

I would never trust or buy from anyone cold calling and my roof tiles are still fine 40 + years on.

 

[tyred]

Algae won't do the tiles any harm. Power washing on the other hand will damage them.

 

[Speicher]

Yes, I was thinking along those lines, but was not sure. Apart from anything else, the roof three doors down, stands out a lot as a different colour from the rest. And surely there is no point as the birds will continue regardless. IIRC bird poo is acidic, but not as harsh as their cleaning method.

 

[goo_mason]

I'm sure this was featured on Watchdog a year or so ago - it was all a big and very expensive con.

 

[Speicher]

I would say if you have no leaks and the tiles are in good shape I wouldnt bother.

I do not want my tiles to be a completely different colour. There was some slipped tiles on the roof last year, and a person recommended by another lady in the street, did a good job of replacing the tiles.

I sent him away with the proverbial flea in his ear. I am concerned about others who may be taken in by his sales pitch. No, I would never give work to a cold caller, might take their leaflet, and then ask around.

 

[Speicher]

I'm sure this was featured on Watchdog a year or so ago - it was all a big and very expensive con.

Yes, it would be. Scaffolding for two days, and the noise .

 

[User482]

Surely this is the definition of a solution to a non-existent problem?

 

[dellzeqq]

tiles. be they concrete or clay, are, to a degree, porous. When they absorb water, and the water freezes, they start to break up - very slowly. If the surface of a clay tile is removed, it will absorb water more quickly. It sounds as if your neighbours have clay tiles, and the surface has been removed. That's probably not good. If the tiles are concrete I wouldn't have thought that they would be anything other than cleaner - but I wouldn't suggest 'cleaning' them.

A lot of school buildings and warehouses were sold off in the 80s, and turned into loft apartments. The brick was sandblasted. It looked brilliant. For a while.

 

[Gerry Attrick]

There are a lot of trees around Attrick towers, and the rear part of the roof is in shade most of the day. I get a lot of moss and algae growing on the tiles and said moss and algae has accumulated/been washed off by rain and wind and re-accumulated since 1976. I'm relieved to say that no rain has penetrated, and whilst that is so my moss and algae are welcome.

 

[Gerry Attrick]

tiles. be they concrete or clay, are, to a degree, porous. When they absorb water, and the water freezes, they start to break up - very slowly. If the surface of a clay tile is removed, it will absorb water more quickly. It sounds as if your neighbours have clay tiles, and the surface has been removed. That's probably not good. If the tiles are concrete I wouldn't have thought that they would be anything other than cleaner - but I wouldn't suggest 'cleaning' them.

A lot of school buildings and warehouses were sold off in the 80s, and turned into loft apartments. The brick was sandblasted. It looked brilliant. For a while.

On what authority are you basing this?

 

[dellzeqq]

long hours specifying tiles, reading the literature, and simple observation.

Clay tiles are formed in a mould. The surface of the tile tends to be continuous. There are air holes within the tile - some you can see, and some are so small you can't see.

 

[Gerry Attrick]

You are way at odds with the expert on BBC's Rogue Traders. This was a bogus selling line by one of the rogue traders they investigated. The RT expert categorically said that tiles do not absorb moisture and consequently freezing temperatures are of no concern whether or not the tiles are covered in moss, algae or (ahem), droppings.