Loft checks

What does a roofer check from inside the loft?

From the loft a roofer sees the roof's underside. Below: the signs of trouble, what ventilation and insulation show, and what to leave alone.

The short answer

From inside the loft a roofer checks the underside of the roof: daylight through the covering, stained or soft timbers, the state of the underlay, wet or missing insulation, ventilation at the eaves and any sign of wildlife. The loft shows faults that the slopes hide, which is why an inspection from the ladder alone leaves out half the picture.

5 min read · Part of Roof inspections

A hipped red-tile roof on a white-rendered bungalow — A torch beam along rafters and underlay in a loft

Daylight, stains and the timbers

With the loft lights off and a torch on, the first look is for light where none should be. A pinprick of daylight is a gap in the covering, a missing tile or a hole around a pipe. Then the timbers:

dark tide marks on rafters and the back of the boarding, which show where water has run
patches of wet or crumbling wood, tested by pressing with a screwdriver tip
white or grey mould on timber, a sign of damp air or a slow leak
rafters, or purlins (the long horizontal timbers that carry the rafters part-way along), that are cracked, sagging or notched
old stains that are dry, which show a past fault, and fresh ones that are damp

A dry stain and a damp one tell different stories, so the inspector notes the position and takes a photograph of each. A moisture meter backs up the eye: a timber that looks dry can still read damp, so a reading is taken at each stain and written down beside its photograph. The eaves get the same attention, because an overflowing gutter may have left the timber at the lowest edge of the roof damp. Our roof inspection checklist shows how these checks sit alongside the outside ones.

Underlay, insulation and ventilation

The underlay is the membrane beneath the tiles or slates. From the loft you can see whether it has torn, slipped or sagged, and whether it is wet. Insulation is checked for damp, gaps, and compression where boards or stored boxes have flattened it.

Ventilation needs a look of its own. With a high-resistance underlay in a cold roof, Marley gives 25 mm of eaves ventilation at 15 degrees pitch or less and 10 mm above 15 degrees, so the inspector looks at the eaves to see whether insulation has been pushed over the gap. Marley classes a high-resistance underlay as not vapour-permeable, so it depends on that eaves gap, and the inspector identifies the underlay type before judging the ventilation. Loose or compressed insulation at the eaves is photographed and noted for the report. A blocked eaves path can leave the loft damp and mouldy, and from a distance that can look like a leak. Our answer on inspections after a storm shows how fresh damage differs.

If the underside of the roof is covered with spray foam, the RICS guide says the timber structure cannot be fully seen or inspected. Speak to your mortgage provider ahead of any such work.

Chimneys, pipes and shared walls

The loft also shows where the roof meets other parts of the building. Around a chimney breast, the inspector looks at the brickwork and the timbers close to it for damp, and at the underside of the lead and flashings where they pass through. Soil pipes, vents and cables that pass through the roof are checked at the point they go through.

On a terrace or semi, the party wall between homes is part of the picture. If work to a party wall is ever needed, such as cutting away a chimney breast, the Party Wall etc. Act 1996 requires the building owner to serve a notice, and the period for that kind of work is at least two months; an adjoining owner may agree to an earlier start by written consent.

Water stains near the chimney can come from the flashing, the pointing, the cap on the stack or a gutter running behind it, so the inspector traces the stain upward and outward before naming a cause. We use thermal imaging as an extra tool where the cause stays unclear.

Wildlife and what to leave alone

Lofts and soffits can hold wildlife. It is an offence to intentionally take, damage or destroy a wild bird's nest while it is in use or being built, and destroying or damaging a bat roost is an offence, intent or not. GOV.UK states that all bat species are fully protected by law along with their roosts, and gives roof repair and roof replacement as examples of the work that falls under that protection. If we see droppings, nesting material or signs of bats, we stop and tell you before anything is moved.

Old boards, lagging and insulation may also hold asbestos. HSE advises assuming that asbestos is present in any building built or refurbished before 2000. A roofer checking the loft looks, photographs and does not disturb anything that could be asbestos.

If you go into your own loft, stay on the joists or a boarded path, because the ceiling below will not take your weight. Take a torch and a phone camera, and avoid touching any suspect material. The main roof inspections page explains how our reports record what is found.