Leaking Roof problems?

The main problems with roofing are:-

that even small problems can cause big results

DIY is hardly ever worth it

Inexperienced roofer repairs often cause more problems than they rectify

Professional design is all important

Collection and disposal of water is vital

Key words when considering any roofing problem or design are:-

Longevity, Lifecycle-Cost, Suitability, Compatibility, thermally-stable, orientation, ease-of-fixture, weight, lap and gauge, pitch, water collection and discharge, is pedestrian use required?, solar reflection, UV degradation, ease-of-repair, access, health-and-safety, jointing, insulation, strength to accept PV or Solar cells, ……..

A roof must keep the weather out, keep the heat in (or out, depending on the season) and be strong enough to not buckle under loadings caused by strong winds and snowfall. In some cases the roof must also be able to withstand atmospheric pollution that corrode and deteriorate even the most rebust coverings.

Environment also plays another factor in design and type of covering considerations: has climates are changing around the world local climates also change and wind speed and direction can many roofing problems. Depending on the direction of prevailing winds a roof will have positive or negative pressures on it at differing times. This means that some coverings must be designed to be fixed down more thoroughly than others (and adjoining walls securely bracket fixed to the roof frame for added rigidity).

As always Planning also plays a part in the design process. Buildings within Listing status or within a Conservation Area may have limited means of being improved to meet new weather or climatic conditions. Maintenance cannot be completed that alters the existing status-quo.

This article cannot cover all the many forms of roofing whether they be pitched or flat: indeed many highly energy efficient buildings nowadays have very small roof areas (if any at all) due to a tapered design and the need to capture rainwater and solar gain etc…… To focus this article let me now centre upon what I have observed to be real issues in 2010. These divide into several categories:-

1. Lack of understanding of new forms and materials by contractors – ignorance

2. Generally poor workmanship – couldn’t care syndrome or fraud

3. Inappropriate repair (often on cost grounds) – being conned by Roofers or poor DIY

4. Lack of appreciation of environmental effects – back to ignorance again

You will notice that I am now referring to existing roofs. As an experienced Surveyor of homes certain things stick out from the norm or are often repeated as errors.

Let’s get down to practicalities: you have a problem that usually involves leakage or deflection of a contour. What do you do? Let’s assume it is not something really simple that can be easily rectified in two minutes.

One slate off a roof. The only way to reset the slate is to metal bracket it back on (otherwise you would have strip off a large band of slates to make the repair unobtrusive and the repair cost would become disproportionate). The resultant repair leaves the base edge of the lead strip visible; known as a ‘tingle” in southern England. When you see many on a slate roof it often means the roof covering is ‘suspect”.

Roof valley (a junction between roof slopes) leakage. Often a bedroom ceiling suddenly becomes damp and you get in the loft and see that a valley is the cause (wetted timbers immediately above the ceiling staining).

In this case lets get back to basics first: is this a leakage due to roof covering faults or a hole in a valley liner? Also we need to check that the problem is located near the visible staining – often the problem is well away from the damage being caused because water tracks along all sorts of pathways.

If a valley liner begins to leak it often creates localised, minor intermittent dampness. The loft is dark and if the loft ventilation is weak then you have the conditions that could favour dry-rot formation. Check the valley lining timbers very carefully for the tell-tale signs of Dry-Rot (discussed elsewhere on this web-site).

Assuming no dry-rot exists we need to discount all potential methods of leakage and assuming none exist then we need to positively verify that an external point source of water leakage exists.

Access then becomes the problem: often you cannot see the problem area and so a Builder with a long ladder is needed (or you must hire a cherry-picker or a scaffolding tower).

The problem could be a blockage in the valley, a pinprick hole in the valley lead, acid-rain corrosion leakage, damage caused by pedestrians (the TV or SKY aerial man who called out last month?), a birds nest, a slipped slate that fell and cut the lead, etc…. It is important to understand what caused the problems so you can seek to not perpetuate the scenario.

Deflected roof slope or contour? This is much more complex. If a flat roof (that must never be completely flat) deflects it will pond with water and deteriorate very quickly. If a pitched roof deflects slightly is might mean nothing important at all.

Flat roofs are not designed to deflect and so diagnosis is easier. I will not dwell here any longer apart from saying that if a flat roof is a rigid structure, such a concrete, and it deflects meaningfully then you need to get advice immediately.

However, if a pitched roof deflects this can be for many reasons. A Surveyor would need to obtain the history of the roof/building as his first method of analysis. Has something upset a longstanding equilibrium? Has a storm caused the problem? – therefore local weather patterns and trends are important to factor into your analysis.

Again the variations on a theme are so many that they cannot be listed here. A good Surveyor will have viewed as much of the exterior as possible, made detailed enquiries and will then inspect the loft space(s) involved. What he is looking for is stress cracks, timbers out-of-alignment, joints opened-up or split, rafters that have twisted, leakages that have caused decay (loss of strength).

What we Surveyors often find is design weaknesses; over-spacing and deficiencies. However, if the frame and liner felt are “performing well” (give them a clap!) then we must filter out the truly abnormal.

Typical defects are:-

· Contractors replaced slates with concrete tiles that are far heavier than slates and did not think to strengthen the frame at all.
· Decay has weakened principal rafters, purlins or struts.
· The nails fixing the slates to the battens have rusted away.
· The slates are delaminating/exfoliating.
· Valleys and flashings have worked loose or are damaged.
· Nowadays a “modern” problem is over-storage (too much weight loaded into the loft).
· Lack of ventilation causing condensation to drip down onto ceilings/insulation.
· Woodworm infestations.

I hope you can see that the complexity of roofing problems is a diverse matter and one that needs expert attention. If is doubt, consult an experienced Surveyor or perhaps a relevant Engineer or older/experienced Specialist Roofing company.