This is not an exhaustive or a complete subject. It is likely to change over time, with edits, additions and deletions, and is simply a collection of my thoughts based on many years of experience. You should follow your instincts, not rely at all on any of this and you must always seek your own professional advice from a skilled, experienced and fully qualified building surveyor.
There is an unmistakeable beauty about traditional clay peg tiles.
The tiles are handmade and no two tiles are absolutely identical. These subtle differences give the roof an almost undulating appearance with variable shadow lines from one row to the next. It is completely different to modern machine made clay tiles. A modern clay tiled roof will sit perfectly flat. Peg tile roofs do not and the undulation is not only perfectly normal and to be expected, it is also an inherent architectural beauty that is important to each property.
These tiles are called peg tiles because they were traditionally hung on battens by oak pegs of about an inch (25mm) long. These tiles are not nailed to the battens. They hang on the battens by their self-weight and gravity. This simple method means that they can be replaced individually without the need for complicated extended repair projects that would otherwise be needed. A peg tile roof is one of the easiest roofs to maintain and, with safe access, could be repaired by a homeowner with reasonably competent DIY skills.
Peg tiles are inherently fragile and will be susceptible to frost damage. You can see this in some of the photos below. The frost will penetrate the outer surface of the tile, causing it to break off and exposing the inner clay. Once this happens, it will get worse each year and the tile will eventually break. Even so, this is an easy repair and the damage itself is natural and to be expected. It is not a ‘defect’ of the roof but instead it is just part of the natural lifecycle.
These tiles are especially susceptible to damage caused by nail corrosion. After the use of oak pegs phased out, there was a use of plain steel nails. These nails will rust, leading to expansion of the steel from the corrosion, the edges of the tiles will crack and the nails can ultimately totally fail leading to tiles slipping off. Traditionally, underfelt was not used. Once a hole forms in the roof surface, from slipped tiles, it should be repaired immediately. A small hole from one tile can rapidly increase to a large hole as the exposed battens will decay and more tiles will slip off. The nails are just as likely to rust through, without causing damage to the tile, but simply losing any strength and then they break and the tile becomes dislodged. This is very obvious and easy to see from the ground with some tiles looking like they have slipped out of place and are dislodged.
Following the use of plain steel nails, galvanised nails were used. It is now more common to find that alloy pins or copper nails are used, as they don’t rust.
In summary, the two most common problems found with clay peg tile roofs are from frost damage and nail corrosion. When this happens, the individual damaged tile should be replaced without delay. It is very easy to do, taking merely a few seconds. Safe access is often the most expensive part of the cost. The tiles are not expensive. Using salvaged, previously used, tiles will often allow for a blended colour that means they are hard to see. Brand new tiles tend to be quite bright until they have mellowed after a few winters weathering.
It should never be necessary to do a 100% replacement of a peg tile roof as long as it has been maintained when needed, on a tile-by-tile basis. This is likely to be every three to five years. Only if the roof has been neglected for decades might it be worth considering a complete strip-off and roof replacement as there is likely to be associated consequential decay and internal damage too.
A common question asked is about moss that can grow on the roof, especially on slopes that face north or have nearby trees. Moss can cause severe gutter blockages when it slips down. You should never use a jet wash spray as this can be too abrasive but it can be a good idea after a period of hot summer weather to carefully brush the roof with a broom to remove the moss. It is especially important to make sure that all gutters are clear and downpipes are not blocked.
Disclaimer: Anything posted in this Blog is for general information only and it is not in any way intended to provide any advice, legal or otherwise, on any general or specific matter that you can rely on. You should always seek your own legal advice.
