It isn’t unusual to see roofs that worked perfectly for years and suddenly no longer fulfil their function properly. If the roofing work was properly executed, why isn’t it doing its job?

Some of the more likely causes are detailed below.


When first applied, roof tiles and other roof components will be in perfect state. However, with time, external elements might affect product performance.

Roof tiles may suffer impacts that will open cracks, fissures or even break them. Applying support structures or similar (such as solar panels) over the roof tiles, moving heavy loads or walking on them might leads to similar damages. When this occurs, the affected elements should be promptly replaced so as not to compromise the roof.

Whenever it is necessary to walk on a roof, as is the case with the installation of antennas, solar panels and similar equipments, walkways should be planned and Torreense safety step tiles should be used.

Accumulation of moss and debris

The basic function of a roof is to be watertight. However, its function may be affected by the appearance of moss and debris.

When this occurs, the roof will no longer function properly, as these elements will constitute obstructions. Water will no longer flow freely and wind may move accumulated water, leading to infiltrations. The solution to this problem is to follow a preventive maintenance plan.

Peeling from the effect of frost

This is one of the most notorious problems a roof may suffer from, and this type of damage will usually be clearly visible.

This problem may occur with clay roof tiles, even if they comply with the EN 539-2 norm. Even when using certified roof tiles in full compliance of relevant specifications, peeling from the effect of ice is always a possibility.

A number of factors contribute to peeling from the effect of frost, such as:

Absence of ventilation, when clay elemets aren’t properly ventilated, their drying time will increase. The mass of the clay piece will be subjected to constant temperature variations for long periods of time, and will therefore be subjected to the frost-defrost cycle. The water present in the clay piece will suffer sudden volume variations, which may ultimately lead to the piece breaking. It is essential that heat and humidity may flow towards the exterior, to retain a balance between the clay piece and the surrounding atmosphere.

Unfavourable geographic orientation, facing the north side will increase the risk of peeling as an effect of the frost-defrost cycle, but this doesn’t mean roofs shouldn’t face north.

Excessive use of mortar and strong mortar will greatly increase the risk of peeling, especially near the ridgeline. Mortar absorbs more water and releases it slower than clay. Clay pieces in contact with mortar are more exposed to frost-defrost cycles and will usually be the first to present problems.

This problem can be prevented by resorting to execution techniques – especially on the ridgeline – that do not use mortar and instead allow for proper ventilation, thus contributing to the optimal functioning and longevity of a roof.

As has been pointed out, this type of problem will be visible near the ridgeline and in areas in contact with mortar. It will usually affect friezes and ribs first and then move on to the hollow (in the case of the Lusa tile).
Once peeling occurs, all affected roof tiles must be substituted. However, in many cases a complete re-roofing will be necessary.

Water infiltration

As has been mentioned before, being watertight is one of the basic functions of a roof. However, infiltrations are not uncommon, and the quality of the products used is not always the cause.
Many factors may lead to the  occurrence of infiltrations, such as insufficient inclination and/or incorrect application of elements. The critical points are:

  • Ridges;
  • Walls and chimneys;
  • Roof tile fittings;
  • Joists (where water converges);
  • Eaves.

It is never too much to emphasise the importance of two fundamental factors that will reduce the risk of infiltrations on a roof: adequate inclination and correct product application.

Differences in tone

Differences in tone are a result of the ceramic process and the use of raw materials. In some cases, different shades are a much sought after aesthetical effect that is intentionally put in place by producing roof tiles with a more thorough finishing work.

However, when the intended effect is a homogenous tone, it is advisable to use differently shaded tiles.

The differences in tone of clay pieces affect merely the aesthetical aspect of a roof and do not interfere with their functional characteristics.