Sagging Roof: Causes and What to Do

From the street, look for a ridge that dips, a slope that bows or a change in shape compared with earlier photographs. Uneven slates alone are not proof that the structure has sagged, and perspective can make a straight line look misleading. Note whether the shape is longstanding or appears to have changed, rather than trying to measure the roof from the pavement.

If the loft is safely accessible from its normal access point, observations such as damp timber, daylight or a distorted support may be useful to report. Do not enter beneath visibly failing timber, step between ceiling joists or disturb supports to investigate. A roof whose shape has changed needs a proper assessment. Indoors, describe any new ceiling movement alongside the external roofline rather than treating them as unrelated issues.

A roof structure carries the covering and other loads through its timbers and supports. Changing to a heavier covering without checking that arrangement can introduce problems. Timber sizes, connections and condition all matter; the weight of an individual slate or tile is not enough to judge the whole roof. Previous alterations are therefore important information even if they happened before you owned the property.

Long-term leaks can allow timber to remain damp and decay. Rafters or sarking that have lost strength may no longer perform as intended. Removed or altered purlin supports can also change how loads are carried, so a tidy-looking loft conversion does not prove the original support remains adequate. These are possible causes, not diagnoses of your home. Explain known alterations and water problems when booking an inspection.

Many Scottish pitched roofs have timber sarking boards beneath the outer covering. Sarking forms part of the roof build-up and provides a surface for other layers and fixings, depending on the construction. Its condition deserves attention when leaks or distortion are being investigated. A sound-looking covering can conceal deterioration below it, while a local damaged board does not automatically mean every rafter has failed.

Sarking is not interchangeable with the main supporting timbers. Boards, rafters, purlins and connections perform different roles, so an assessment needs to distinguish them. Replacing the visible covering without checking affected timber can leave the underlying cause unresolved. Ask which parts can be assessed at the initial visit and which might only become fully visible once an agreed area of covering is opened.

The severity depends on the cause, the extent of movement and whether it is progressing. An old uneven roofline is not the same situation as a newly moving roof with damaged supports, but neither can be declared safe from a description alone. New distortion, falling materials or visible timber failure should not be left for a cosmetic repair discussion.

Keep people away from an area that appears unstable and do not load the loft with stored items while support is in question. If there appears to be an immediate danger to occupants or passers-by, prioritise safety and seek appropriate emergency assistance. For roofing enquiries, describe the change clearly. Our roof leak guide covers moisture symptoms, while this guide focuses on the shape and support of the roof.

A local timber defect may be capable of a defined repair where the remaining structure is suitable. More extensive decay or an unsuitable support arrangement may need wider work and structural advice. Renewing slates over a dipped surface, or adding material to make the line look straighter, does not establish that the roof can carry its loads safely.

Rowan Roofing's roof repairs, new roofs and roof replacements pages explain the existing roofing services. The inspection and written quote should identify the roof work proposed and any further assessment needed. Do not assume that every structural issue is included in a covering quote; establish what needs resolving before selecting the finish or agreeing how much of the roof will be renewed.

Send safe photographs of the ridge and slopes, explain when you first noticed the change and mention known leaks or alterations. Old photographs, previous roofing paperwork and information about changes in the loft can help the assessment. You do not need to identify a purlin or name the timber before getting in touch. Describe what has changed in your own words.

Read how long a roof lasts if you are also weighing up the general condition of the covering. Age and sagging answer different questions: a relatively sound surface does not rule out a support problem. Call 07508 571291 or send the details through our contact page. Ask for the findings and proposed scope to be explained before deciding between a limited repair and a wider roofing project.