There are 2 main reasons why roofs have a reputation for being intimidating.  Firstly, working at height tends to be a little scary if you’re not used to it. And secondly, when roofs go wrong they can punch a huge hole in your budget.

To make matters worse,  TV Rogue Trader  programmes seem to invariably feature cowboy roofers. So it’s little wonder that many of us dread the sight of a leaking roof.

Such apprehension is compounded by the fact that roofers’ estimates are notoriously baffling, carefully laced with (often inappropriate) technical terms designed to bamboozle the customer into whimpering cheque-signing submission. So who can you turn to for advice?

Chartered surveyors offer professional impartial advice, but sometimes suffer from a tendency to err on the side of caution –  conscious that no one gets sued for being overly pessimistic  – so anything that looks a bit dated may get unfairly condemned as ‘nearing the end of its useful life’.

Unfortunately, roofs are more likely to suffer from defects than many other parts of an older building. Which is no real surprise given that they’ve often had to withstand driving rain, baking heat, storms and blizzards for a century or more.  Clearly, this is one part of the property that it is essential to check thoroughly prior to purchase. So what defects should you look for on an older property?

First, consider what kind of coverings you are dealing with. The traditional roofing material on many period properties was hand-made clay tiles, or perhaps ‘stone slates’ in some rural areas.

Georgian townhouses popularised the fashion for lightweight natural slate which became almost universal on Victorian  dwellings until superseded later in the 19^th century by manufactured plain clay tiles. Large wavy pantiles and Roman tiles were a popular regional variation  in areas such as East Anglia. From the late 1930s, clay tiles started to be gradually superseded by concrete tiles.

So question number one has to be ‘does the property still have its original roof coverings ?’

If the answer is ‘no’ it may not altogether be good news. Generous Council grants in the 1980s provided the incentive for many  Victorian properties to be unnecessarily re-clad with large heavy Redland concrete interlocking tiles – the main attraction of which was their cheapness and ease of laying. Plenty of cowboy firms failed to beef up the roof structures to take account of the substantial extra loadings – resulting in extreme sagging, and in some cases, collapse.

Today, modern artificial slates (composite fibre) are generally considered to be a suitable, cost-effective alternative to real slate, although earlier asbestos fibre artificial slates haven’t lasted well and may now be due for replacement  (when contractors get wind of the ‘A’ word this can prove costly ).

Lifespans of roof tiles and slates

As you can see from the table below, the lifespan of traditional handmade natural roof coverings was far superior to modern manufactured stuff.  In fact it tends to be the fixings that fail first. Slate roofs commonly suffer from corroded nails,  and ancient ‘peg tiles’ or stone slates may start to slip due to rotten timber pegs. Salvage yards can bear witness to the longevity of such traditional materials,  normally being well stocked with handmade clay tiles and recycled Victorian slates awaiting their second incarnation.

Things to check on the outside

It will pay dividends to spend a few minutes casting a critical eye over your roof. There are a number of  clues to possible problems that can be spotted fairly easily:-

1. Look down the street at nearby houses of the same age – if  any have new roofs, there’s a greater chance that yours may also need to be re-clad.

2. Are the main roof slopes reasonably level and even ? Slight settlement is not usually a problem and is particularly common next to gable ends where the rafters have settled more than the adjoining masonry. If  the ‘dishing’ is more pronounced, then it may be the result of  past recladding with heavy concrete tiles, so you’ll need to check the support in the loft (see below). If the structure is satisfactory and there’s no leakage, a fair amount of historic settlement can be acceptable.

3. Are there many slipped or missing slates / tiles, or any that are sticking up ‘proud’ (usually due to poor repair work)?   The need for some localised refixing is not unusual.  The odd slipped slate can be re- fixed using small folded metal clips known as ‘tingles’,  but if there are more than a handful of tingle clips on one roof slope, the need for complete stripping and recovering may not be too far off.

4. Pay careful attention to all roof junctions. These joints are covered with flashings – a major weak point.  The worst offenders are cement mortar ‘fillets’  which are very prone to cracking and should be replaced with lead flashings. But even good quality original lead or zinc flashings may now be living on borrowed time.  Another weak point is at the valleys where two adjoining roofs meet (e.g. where a bay roof joins the main slope). These are typically lined with lead sheet and pointed up with mortar at the sides. The pointing tends to crack and fall out in lumps and the metal can suffer corrosion from acid rain pollution.

5. The ridge tiles running along the top of the roof commonly suffer from eroded mortar joints and may need pointing up, or even re-bedding.   The ‘verges’ at the edge of a roof slope also commonly require routine maintenance in the form of pointing up with mortar.

6. Many early Victorian townhouses  had Georgian-style ‘butterfly’ roofs, hidden from view by a front parapet wall. Cetral valleys running from front to rear above the bedroom ceilings are prone to neglect, blockage and leakage. Anticipate the significant expense of  re-lining and replacement of rotten support timbers.

7. Victorian flat roofs were commonly clad withlead, or cheaper zinc, both of which will now be well past their prime. Modern flat felted roofs can have a lifespan as short as 12 years. Flat roofs are of course not flat, but need a minimum 1:40 slope to disperse rainwater and prevent ponding;  many fall short of this requirement and the decks may need upgrading.

Things to check on the inside

To fully assess the condition of a roof, you cannot overlook the structure. Popping your head into the loft space (assuming there’s a loft hatch) can tell you a lot about the wellbeing of the property.

* If your loft is draughty and there’s no underfelt below the slates or tiles, don’t be alarmed – that’s the way it was built. Felt provides a secondary line of defence against driving rain, but was only widely installed on new houses from the 1950s. Old roofs rely on decent ventilation so that any rain that blows in can safely evaporate away. There may be small chinks of light visible between the rows of tiles or slates, which is normally OK. But any larger gaps, particularly at roof joints can spell trouble.

*  The main rafters on each roof slope  are normally supported by a large horizontal beam called a purlin, which in turn usually employs a wooden strut for support. If the roof sags, improved support may be necessary here. This is fairly simple carpentry and shouldn’t be too expensive, if access is reasonable.

* White powdery salts under the tiles can be indicative of erosion. Especially check the condition of the projecting ‘nibs’ at the top of each tile (where they are hung from the battens).  It is also here on the underside that slates tend to first soften and ‘de-laminate’  indicating the need for renewal.

*  Check  whether the firebreak party walls are in situ. If not they will need to be built up in lightwieght thermal blockwork or fire-resistant plasterboard.

Finally, it’s worth bearing in mind that many original roofs will exhibit very few of the above defects and will be perfectly satisfactory with a little routine maintenance from time to time. Premature replacement is an unnecessary expense and roofers may well utilise inferior cheaper modern materials.