Element Spotlight – Pitched Roof Coverings

There’s nothing more important than keeping a property dry and that starts with the roof covering. Pitched roof coverings broadly breakdown in to two categories; tiles and slates. Corrugated sheeting and felt is occasionally used but that tends to be on temporary buildings so won’t be covered in this post. Roof structures and weathering will be the subject of separate posts later in the series.

Tiles

Roof tiles were originally hand made from clay, but these days are generally concrete with clay only being used where it is necessary or desirable to match an existing covering due to the cost. Clay tiles are approx. 50% more expensive than their concrete counterparts with that difference increasing to 100% for the hand made variety.

Clay tiles are generally plain in appearance whereas concrete tiles can be profiled.  The most common example of a profiled tile is the Redland 49 which became ubiquitous in the southeast of England after the war when they were mass produced as a cheap alternative to clay.

Tiles are manufactured with 2 nibs at the top which hook over horizontal timber battens that are nailed to the rafters. They also have nail holes but the number of rows that are also secured with nails depends upon whether the tiles interlock and the pitch of the roof.

Read about common defects affecting tiled roof coverings.

Slates

Natural slate will already be millions of years old by the time it is fixed to a roof so it is not the slate itself that dictates its longevity but the fixings that secure them. Still, a slate roof fixed with good quality copper nails should last well over 100 years.

The big change in the slate market in recent decades was the introduction of artificial varieties. Artificial slates had been used as far back as the 1800s, but it was only when producers managed to manufacture a product that looked like the real thing and did not contain any harmful materials that they took off in a big way.

The most common roof covering used on new build properties in recent years is fibre cement artificial slates. They have the advantage of being cheaper than natural slate, particularly the quality Welsh slate that had traditionally been used in England, and being machined to an exact size. The range of artificial slates available continues to grow as manufacturers overcome some of the early issues of discolouration and brittleness and recycled plastics are now used. The life expectancy of artificial slates has extended from 25 to 50 years as they have evolved.

Read about common defects affecting slate roof coverings.

Sarking Felt

An important aspect of any roof covering is the sarking felt. The felt is fitted below the battens and takes any rainwater that penetrates the covering, due to driving rain, cracked tiles etc., down to the gutters.

Early versions of sarking felt, used from around the 1930s onwards, were bitumen based and were air as well as water-tight. Roof spaces fitted with this type of felt required vents to reduce the risk or decay and infestation.

Polypropylene breathable membranes became common in England in the 1990s. The design allows air to pass through pin size holes while remaining water resistant. However, some manufacturers still recommend vents at the ridge and/or eaves,

Sarking felt should be installed so that it sags between the rafters and effectively creates a channel to direct moisture to the gutter without touching the battens.

Read about common defects affecting sarking felt.

Over time, I’ll add examples of typical defects to the posts linked to above.

If you live in the Cambridgeshire of north Essex area and would like a quote for an RICS Home Survey, please contact us for a quote on 01799 543532 or via email.