Checking Your Roof From the Loft: A Homeowner's Guide

Start with the basics. Tell someone you are going up, take a torch and your phone, and wear a dust mask and long sleeves. Open the hatch fully and check what is on the ladder side before you step.

Keep your weight on the joists, the timbers the ceiling below is fixed to, or on boards laid across them. The plasterboard between joists will not take your weight. Keep your head below the rafters, because roof nails sometimes poke through the underside. If the loft is boarded for storage, lift only a board or two where you want to look, not the whole floor.

Is it safe to go in if the house is old?

Think about asbestos first. HSE's advice is to treat a home built or refurbished before 2000 as containing asbestos until shown otherwise. In a loft the likely places include old insulation boards, textured coatings, pipe lagging and any cement sheet. Do not drill, scrape or break anything you cannot identify, and do not sweep up dust you are unsure about. Look, photograph and leave it.

Hot weather makes a loft unpleasant, and a wet or windy day makes it hard to read. Choose a dry day with decent light outside, because that is also what makes daylight leaks visible. And if you have a bad back, poor balance or no wish to be up there, a roofer's loft photographs do the same job.

Once your eyes have settled, turn the torch off and look up. Pinpricks of daylight coming through the roof slope mean a gap in the covering. A slipped slate or a missing tile shows as a bright patch, and a thin line of light around a flashing or along the ridge suggests a joint that has opened up.

Daylight is not always a leak, because a sound roof of slates or tiles with open laps can show a glow at some edges. The test is the pattern. A few bright points scattered across a slope tell a different story from one bright patch below a ridge or a chimney.

What does daylight at the eaves mean?

At the eaves, a little light and a draught can be deliberate. A cold roof needs air to enter along the eaves, so you will often see a gap there. Light coming through the face of the roof, away from the eaves, is the thing to note.

Photograph each spot with your phone, with a quick note of where it is: which side of the house, how far along, and how far up the slope. A roofer can match those pictures to the outside and find the fault from the ground, instead of searching the slope. Mark nothing with a pen on the timbers or slates, and do not push at the covering to see if it moves. Our guide to inspecting your own roof covers the outside half of the same job.

Water leaves marks. Sweep the torch slowly across each rafter and the back of the covering, looking for dark tide lines, which are rings or streaks that show where moisture has dried and returned. Look at the corners where the roof meets the wall, below chimneys and under valleys, where the sloping channels between two roof planes catch the most water. Check the area around the loft hatch and any pipes or flues that pass through the roof as well, since each one is a hole that has to be sealed.

Feel the timber with the back of a finger where you can reach it safely. Damp wood feels cool and soft. Dry wood feels firm. A fine white or grey fuzz on timber is mould, and a powdery brown crumble is a sign of decay.

How can I tell a leak from condensation?

The pattern gives it away. A leak leaves staining in one place, usually below a defect such as a slipped slate, a cracked flashing or a worn valley, and it is worst after rain. Condensation spreads across the whole underside of the roof, shows as beading on the felt and timbers and as damp insulation, and gets worse in cold weather. Our guide on loft condensation after a new roof explains why it can appear after work.

Check the insulation too. Compressed, darkened or soggy patches show where water has dripped. Look at the chimney breast for brown stains, and at the ceiling below for a ring that matches. If you find fresh, active wetness, take photographs and call a roofer promptly. Putting a bucket and a plastic sheet under a drip is a sensible stopgap while you wait.

Underlay is the sheet of felt or membrane beneath the slates or tiles, which catches any rain that gets past them. Many older roofs have none, and you look straight at the back of the slates and the timbers. Where it is present, check that it is whole.

Warning signs are tears, sagging between rafters, patches that look brittle or crumbling, and daylight through holes in it. A tear is a hole where water can enter. Underlay that has slumped can hold water and pass it to the battens. Check around the chimney and the eaves in particular, where underlay is cut and lapped most often, and where a small tear or a missing lap is most likely to have been missed.

How do I tell if the timbers are sound?

Next come the battens, the narrow timber laths that hold the slates or tiles, and the rafters, the sloping beams beneath them. You want straight, dry, pale wood. Warning signs are dark staining, splits along the grain, sagging between supports, rusty nail heads and crumbling dust on the insulation. If a batten feels spongy under a gentle press of the thumb, it has been wet for too long. Do not poke at timber near broken underlay.

Our guide to whether roof battens need replacing goes into rot versus undersizing, and our page on roof underlay types compares the materials you might meet. Look at the main roof timbers too. Any cut, notched or bowed truss should not be touched, and photographs are all you need.

Bats roost in lofts and under old slates, and GOV.UK describes every bat species as fully protected by law. If you see droppings or hear squeaking, leave them undisturbed and tell your roofer before any work starts.

A roof space needs moving air to carry moisture out, or it condenses on the cold surfaces. What that looks like depends on the type of underlay.

Where the underlay is HR, which is non-breathable, Marley's guide for a cold roof asks for a 25mm gap running the full eaves length on pitches of 15° or less, and 10mm on steeper pitches. Breather underlay, called LR, is different: over a well-sealed ceiling Marley relies on the 3mm gap that ordinary eaves construction leaves, provided the product carries third-party certification. The code behind these figures is BS 5250, which covers managing moisture in buildings.

Is my insulation blocking the eaves?

Look at the eaves with your torch. Insulation pushed hard into the corner, or a roll laid over the gap, stops air getting in. Vents may also be painted over or blocked by old felt. If air cannot enter at the eaves, you may see damp timber and mould on the underside of the roof close by.

Do not remove insulation to fix it. A roofer can fit eaves ventilators and trays that hold the insulation back while keeping the gap clear. Our condensation guide and the Marley gaps above are a starting point, and each roof needs its own check. A loft that is stuffy, smells musty or has water running on the underside of the covering after a cold night has a ventilation problem to solve.

Take photographs as you go, and keep them together. Aim for a wide view of each slope, then a close shot of anything that worries you, with something in the frame for scale. Note the date and the weather. These are what a roofer, a surveyor or an insurer will look at first.

Then sort what you found into three piles. Things that need action soon include active drips, daylight through the covering, torn underlay and soft timbers. Things to watch include old stains that are dry, minor condensation and marks near the eaves. Things that are fine include dry pale timber, whole underlay and clear airflow.

When should I call a roofer?

Call if there is fresh water, soft or split timber, daylight you cannot account for, or damp insulation. If you need a written record for a sale, a claim or a worry about the age of the roof, a proper inspection covers the outside as well, and the loft pictures you took give the surveyor somewhere to start. Our page on roof inspection reports sets out what a useful one contains.

If you may claim on your home insurance, phone the insurer before anything is repaired, then keep dated photos and every receipt for a temporary fix. The Financial Ombudsman handles complaints that stay unresolved. Do not climb out onto the roof to investigate, whatever the loft shows.

If the loft says something is wrong, ask for a survey: we check the outside against your loft pictures and send you photos of the cause, plus one written price for putting it right.