Do Concrete Roof Tiles Need to be Re-Sealed?


During the last five years or so I have seen a distinct increase in the number of companies offering to colour, seal, coat or paint old roof tiles. You may well have noticed this surge too?

Perhaps like me, you have also been bothered by pesky door-to-door canvassers or seen eye catching leaflets put through your door?

There is one question I really wanted to address:

Do concrete tiles actually need to be re-sealed?

Re-sealing is the process of applying a waterproof coating to the surface of the tile in an effort to keep rainwater off the tile.

Let’s Dispel a Myth

One common myth, often used by salesmen is that old concrete tiles will become porous and water will seep through them and into the property.

Actually this doesn’t happen at all.

Old tiles that have had decades of weathering will keep rainwater out of the house regardless of whether they have a waterproof seal on the surface or not.

Because tiles are laid on a pitched roof (a sloped roof) water runs off the tile and onto the next tile below. The water continues like this until it enters the gutter.

The way tiles are laid (i.e not flat) means that even a porous material like concrete wont leak. Gravity pulls the water not into the roof but down onto the tile beneath – don’t forget that all tiles are overlapped.

That is how a porous material like clay or concrete can be used on roofs. In fact most roofs in the United Kingdom are made from materials that could be considered porous. They normally only leak if the roof pitch (slope) is too shallow or if a tile breaks.

So Why Seal Roof Tiles?

There are a couple of advantages to sealing roof tiles but in my opinion they certainly do not outweigh the disadvantages.

I will leave it to you to decide for yourself:

Advantages of sealing tiles:

Stops water from entering hairline cracks where it could freeze and potentially crack the tile or roof cement (water expands when it freezes)

Stops rainwater from weathering the surface of the tiles – possibly extending the life of the roof by a few years (please see the disadvantages below)

Disadvantages:

To apply the sealant one must first thoroughly clean the tiles, i.e with a pressure washer. This actually strips the surface off many types of tiles and shortens the life expectancy of the tile. There is also a flood risk involved with pressure washer use (see this BBC Rogue Traders episode as a good example)  and of course the tradesman will need to walk all over the tiles, at least several times, this increases the chances of breaking tiles. I have already covered this on another page titled is it safe to use a pressure washer on a roof?

Roof sealants also tend to wear off after a few years, all that rainwater flowing down the pitched roof, it shouldn’t be a surprise that a lick of paint or sealant won’t last long here. You may want to think about what a roof looks like when sealant starts to peel off. Here are some photos you may want to explore.

It’s an expensive exercise, all the preparation work for a short term product. If the process needs to repeated every 3-8 years then it just isn’t cost effective at all. It would be much cheaper to have the roof checked every few years and any cracked tiles replaced.

So to Answer the Question…

No, concrete tiles do not need to be re-sealed, the process is entirely optional. I have seen concrete porous tiles on very old roofs and not one drop of water has entered the property. The pitch of the roof and the way tiles overlap means water cannot seep through them directly.

Most salesmen who sell roof coatings won’t tell you that though. ( Here are some tips on what to expect from dodgy roof coating salesmen)

If you decide that you still want to go ahead with tile re-sealing then that’s fine but hopefully you won’t be doing so because some door canvasser has told you your tiles are becoming porous and you need this “miracle” sealant.

Hot Tip:

If you really have been hoodwinked into  sealing or coating the exterior of the tiles, then you could consider using a clear/translucent sealant. At least when it starts to wash off/peel/crack etc you won’t be able to see it! And of course your roof won’t look like this:

Coloured sealant peeling off roof tiles

Click to see high resolution

 

 

Trading Standards

Ever wondered what your local Trading Standards Office has to say about roof coatings? Did you know that the BBC Rogue Traders programme has featured several of these coating companies. Find out more here.

Further Reading

Did you like this article? Why not “like” us on Facebook and then try one of the following links:

Is it safe to pressure wash a roof? (Advice directly from tile manufacturers)

How to clean a roof without pressure washing (what most roof coating companies don’t tell you!)

Roof coating scammers found guilty in £2.4million scam (wow!)

Yet another conviction in the roof coating industry

Are thermal roof coatings the biggest scam in the roofing industry?

Can You Help?

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Discuss: “Do Concrete Roof Tiles Need to be Re-Sealed?”

  1. January 16, 2013 at 10:06 #

    Some good points made here, concrete tiles are porous, and as stated this is unlikely to ever cause water to pass through them (to any extent worth mentioning) and anyone that claims it will is certainly talking rubbish.
    And no, tiles certainly don’t need coatings, clear or coloured.
    But you should also make clear that roofs will always get dirty and discoloured, even newly tiled ones!
    Coatings “properly” applied should last many years, well beyond ten in most cases, which if applied at reasonable costs, makes it a much more worthwhile proposition, wouldn’t you rather have a coating wear away than your tile surface?
    Proper coating products will not wash off with the rain either, or peel, and the best of them have solid ten year guarantees now.

    Posted by Alex Duncan
  2. August 3, 2013 at 12:25 #

    That woman who said decorative only is wacko.
    Read myths

    Posted by Rich
  3. August 25, 2013 at 02:26 #

    when the pigmentation degrades in man made concrete tiles and the tile surface as been through years of hail, storm, wind ,ice, rain, the tile will weaken with age the tile structure will lose its integrity and will absorb water resulting in your tile battens becoming constantly damp and more weight will be added to your roof.
    You should consider contacting a good roof coating installation company who could advise you if a coating is possible or not if a roof renovation is achievable this will save you a lot of money and will stop any more damp ingress invading your roof tiles for many years to come.

    Posted by Gary
  4. November 9, 2013 at 13:46 #

    Hi, thanks firstly for a nicely put together article, but I must add my personal experience. I have a chalet with concrete tiles that was constructed in 1959 and tiles are original which makes them 54 years old.
    Having the roof exposed (no underfelt so easy to view from below) I can clearly see ingress of water on several tiles that culminates with a drip forming. These leaks are in the centre of several tiles and not due to cracks, also the tile thickness is not noticeable reduced on offending tiles so this must be water passing through the tile, note also that the patches of water that form are local i.e. not a result of water flow from tile above.
    As a single storey build my chalet roof is easily accessible and I’ve studied/observed this occurrence throughout a six month period from above and below so this is a thorough and ongoing investigation.
    Result from my experience therefore:- Certain concrete tiles DO allow water penetration.

    Posted by mark green
  5. January 13, 2014 at 20:19 #

    As a member of the advisory committee of our gated community in central Florida, all 2000 residents are required to pressure wash their roof if the concrete tiles become discolored by mold. The cost to pressure wash will run between $300 to $500 which depends on the amount of rain and the quality of the tile construction. This will directly determine the frequency of pressure washing. In the last few years the average has been every two years. At this time I am researching a tire sealant with a 5 year warranty to cut the cost to our residents. Understand that once the sealant is applied under no condition should anyone be on the roof without a harness and a second person to prevent slipping off.

    Posted by Bill Diaz
  6. January 23, 2014 at 22:12 #

    Hi thanks for the info good to read .as I have spent days cleaning my roof after many many years of weather and mould .moss build up I have had to replace a few tiles and the bloke I got replacements off said no need to spray on a sealant as will be lucky to last six months and as he’s a tiler himself said best protection was the build up of natural defense e.g.moss etc .and if the roof is laid correctly as you say water will flow away anyway have done it now ..mist say it looks ok and now will fit solar panels and paint the house…then no doubt ..she’ll find something else to do for me …cheers Ian

    Posted by ian wison..bris australia
  7. January 29, 2014 at 15:24 #

    I had my roof coated 2 years ago at a cost of £3000 (half price offer), it has a 15 year garantee but the company no longer exists, this is because of all the complaints and call backs for leaking roofs.
    I have since found out that I could have had the roof retiled and felted for under £2000
    I still struggle with dampness and leaks and the nice paintwirk has moss growing on it already.
    This coating process is a complete waste of money . Do not ever get suckered into it.

    Job done by PRESTIGE ROOF COATINGS of Eccleston Lancs, they most likely now operate under a different name

    Posted by john
  8. February 18, 2014 at 07:37 #

    You could not have and your roof re tiled for under 2000. I don’t even know what size roof you have, but know scaffolding alone is going to set you back at least £500. Tiles, for the cheap Redland plain are going to set you back again at least £500. Then we have battens, felt and disposal of old materials. Then add labour. Minimum of 1 day tile and Barton removal, 1-2 day felt and batton installation and one day tile and ridge installation. Minimum of 180 per person, per day. 2 man job. £1440 on labour alone. New roof for under £2000? That’s just a roofer saying so to make our job look expencive. Take him up on his offer and watch him mumble, we are a booked for the next 20 years I’m afraid. I could clean and coat your roof and replace all broken tiles for £1000. We have been going over 3 years and are going nowhere! We can even replace ridges with a dry ridge system and also verges,and remove chimneys. We have done many in my local town (never cold calling) which still look as new. We mix the fungicide into the paint to help prevent it returning so quickly. A couple had the roof scraped only 18 months ago and it has moss balls forming already. But what do you expect, it was never clean properly and looked awful once finished. All streaky with dirt once the fungicide attacked the mold on the tile.

    http://www.roofrestorer.co.uk

    Posted by Tom