moss on a roof

  sunnystaines 10:53 29 Jun 2013

is it a problem, got concrete stle large tiles and a few small clumps of moss, but got a slating down from a surveyor report. I thought they were harlesss unless there was a mass of the stuff like a blanket.

should I scrap it off or leave it.

  iscanut 11:28 29 Jun 2013

I have had moss on both sides of tiled roof for over 35 years and have never touched it. It does not seem to be a problem.

  sunnystaines 11:33 29 Jun 2013

that is what i thought had a surveyour check out our house and this was one of the ints we were wrote down on.

thanks for the reply.

  BT 11:50 29 Jun 2013

I have clumps of moss on my roof and most of it seems to fall off in time when the clumps get to a certain size. The birds seem to like having a go at it now and then and knock lots of it down. Most of it lands on the floor but some ends up in the gutters which needs removing occasionally. There were some huge lumps on the conservatory roof but a heavy rainstorm washed it off.

  iscanut 13:48 29 Jun 2013

BT..I know the problem re the birds. They seem to think that the moss clumps are full of worms. Yes, I have to clear gutters now and again but the moss does not appear to have damaged any of the tiles or intruded inside over the 35 years or so. I am told that power washing can damage the surface of tiles and I have left well alone.

  Forum Editor 15:30 29 Jun 2013

Moss on a roof can become a problem.

If it builds up to any extent it will tend to hold moisture against the roof tiles, and in winter the repeated freeze/thaw cycle can lead to a degradation of the tile surface.

In addition, the moss will gradually fill gutters, leading to rainwater over-spill.

A moss-covered roof is not a good thing - you need to deal with it. There are various ways of doing this, but the most effective long term treatment is a copper strip that is inserted into the ridge tile mortar bed along the length of the roof. Rainwater will wash a weak copper sulphate solution down the roof over a long period, and this will deter moss growth.

You can buy 50mm wide copper strip in rolls for the purpose. An alternative (and somewhat easier) way to achieve the same effect is to fix purpose-made angled copper to the tops of the ridge tiles.

Whatever you decide, do something. Moss on the roof is a ticking time bomb. It may be a slow tick, but it will cause damage in the end. You'll not know about it until the tiles begin to break up and slide down the roof.

Concrete tiles stand a better chance than clay - they are very dense, and more frost-resistant.

  sunnystaines 17:43 29 Jun 2013

fe thanks will hose it hose.

  sunnystaines 17:43 29 Jun 2013

hose it off

  morddwyd 19:45 29 Jun 2013

I had a similar thread to this last year when my insurance company refused to pay out for storm damage which they said was caused by moss.

When I asked a local roofing contractor to clear the moss they said they would if I insisted but they didn’t recommend it.

They are a reputable firm who maintain the mediaeval roofs of the older parts of St Andrews University.

When I told my insurance company of this they asked for a copy of the contractor’s advice.

I suggest you ask your insurance company which practice they favour. They might refuse a legitimate claim because of moss on the roof, but they are just as likely to refuse it because you have had the moss removed!

  Forum Editor 01:48 30 Jun 2013

There are obviously different schools of thought on this issue. Mine is in favour of moss removal. I've seen documentary evidence of many instances where large amounts of moss on a roof have formed effective blocks against proper rainwater drainage. Modern interlocking concrete tiles have small drainage channels built into their edges, and these can become blocked by moss growth, causing rainwater to seep through onto the sarking below. Over time this causes the tile battens to rot, allowing tile slippage.

  morddwyd 19:33 30 Jun 2013

For some reason a bit of my post went missing yesterday.

The Roofing Contractors Federation do not recommend the removal of moos, they believe, in general, that it does more harm than good.

This thread is now locked and can not be replied to.

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