Dismantling traditional timber roof structures

The usual reason is a leak that has gone on for years. Water slowly rots the rafter ends, the wall plates and the joints. The timber softens, cracks and loses strength, even though the roof may still look fine from the outside. In practice the real condition often only shows once the roof covering is off.

A careful look in the loft is worth the time. Watch for these warning signs:

• Dark stains and a musty smell
• Fine, powdery dust under the beams, a typical sign of wood-boring insects
• Soft rafter ends that a screwdriver goes into easily
• A sagging roof line or cracks in the timbers
• Old botched alterations, such as beams cut out with nothing to replace them

You do not always have to remove everything. If only a few members are damaged, a carpenter or structural engineer may suggest a partial strip-out and replacement of specific timbers. With widespread fungal decay or insect attack, though, replacing the whole frame is usually the more sensible choice, so the problem does not carry over into the new roof.

Everything starts with a site visit. An experienced carpenter checks the condition of the timber, the type of roof covering, the pitch and height of the roof, the state of the chimney and gable walls, and access to the house. Only then is the method decided.

1. Inspect the roof and decide on full or partial removal.
2. Put up scaffolding, set up fall protection and fence off a danger zone around the house.
3. Have a qualified electrician disconnect the wiring in the loft, and check that no other services run through the ceiling.
4. Strip the roof covering, battens, counter battens, flashings and gutters.
5. Prop the weak or risky parts of the frame temporarily.
6. Release the members in small sections, starting with the lightly loaded ones and finishing with the main load-bearing timbers.
7. Lower the timbers to the ground in a controlled way, never throw them down.
8. Sort the material, take it away and clean the ceiling and the tops of the walls.
9. Cover the open building against rain if the new roof frame does not follow straight away.

Why does the order matter so much? In a traditional cut roof the members brace and support each other. Cut a purlin or a post too early and a larger part of the roof can shift, loading a gable wall or ceiling that was never built to take it.

Two houses with the same roof area can mean very different jobs. A bungalow with a simple pitched roof, good access from the street and room for a skip right next to the house is the straightforward case.

These things make the work harder:

• A taller house and a steeper pitch
• A complex roof with dormers, valleys and chimneys
• Badly decayed timber that needs more propping
• Heavy or brittle roof covering that breaks as it comes off
• Tight plots where material has to be carried by hand through a yard or the house
• Hazardous materials that must be removed separately

When you compare quotes, look at what is included, not just the total. Check whether the quote covers the roof covering, scaffolding, skip hire, waste removal, clean-up and temporary weather protection.

This is work at height on old and often weakened timber, so stripping the roof of a family house yourself is not a good idea. The contractor should provide fall protection, safe access, helmets and harnesses, and keep everyone out of the area where material could fall. In terraced or semi-detached houses the neighbours' property, windows and cars need protecting too.

Removing a roof frame is work on the load-bearing structure. Building regulations differ from country to country, so always check with your local building authority whether you need to notify them or apply for approval, especially if the shape, height or pitch of the roof will change. In a block of flats, nothing starts without the agreement of the building management or owners' association.

Older roofs often have fibre cement slates or corrugated sheets that may contain asbestos. Only a licensed asbestos contractor may remove them, following an approved method. Do not break or cut them yourself.

An ordinary roof produces a surprising amount of material. Sorting it on site saves trouble later:

• Timber: rafters, purlins, battens and ties
• Roof covering, sorted by type
• Metals such as nails, screws, fixings and flashings
• Mixed construction waste and old insulation

Sound beams with no rot or insect damage can be reused for sheds or garden structures. Rotten, infested timber or wood treated with old chemical preservatives does not belong in a new structure and should not be burned in a stove or fireplace either. Agree in advance where the skip will stand and who takes away what.

• Starting without an inspection and trusting how the roof looks from outside
• Cutting timbers without temporary props
• Throwing heavy pieces off the roof instead of lowering them
• Leaving the house open to the rain
• Putting all the waste into one skip
• Not agreeing how extra work will be approved if hidden damage turns up

Before you sign off the job, walk round the site with the contractor and check:

• The agreed scope has been removed and any retained members are stable
• The gable walls, chimney and ceiling are undamaged
• The tops of the walls are clean and ready for new wall plates
• Any hidden damage to the masonry or ring beams is recorded and photographed
• The building is covered against rain if the new roof frame does not follow straight away
• No nails, broken tiles or bits of insulation are left on the ceilings
• The waste has gone and you have a receipt or waste transfer document for it
• The surroundings, facade and windows are free of damage