The short answer
It depends on who owns the block and what your agreement says. A tenant renting from a council, housing association or private landlord normally reports the leak to that landlord. Owners in a block with shared title or a management company follow the lease or the rules of the company. Do not touch asbestos-cement sheets yourself, and photograph the damage before you report it.
Start by finding out who owns the roof
A block of lock-up garages is rarely owned by the people who use the individual doors. Possible owners include a local authority, a housing association, a private landlord, a management company set up when the estate was built, or the garage owners jointly. Each one leads to a different answer.
Look at the paperwork first. A tenancy or licence agreement for a rented garage will say who is responsible for the structure and the roof. A lease for a garage sold on a long lease will usually say the landlord or a management company maintains the roof and the garage owner pays a share through a service charge. A freehold garage in a terrace of lock-ups often has a covenant, or a deed, or nothing written at all, and then the neighbours have to agree among themselves.
If the documents are missing, the person who collects the rent or the service charge is the first person to ask. Jot down names and dates of every conversation, as you may need them later.
What to do when the roof leaks
Photograph the damage as soon as you see it: the drip, the stain on the ceiling, the damp on the floor and anything stored underneath. Take pictures of the roof from the ground if you can see the problem. Move belongings off the floor and away from the worst of the water, because a landlord's responsibility for the roof does not usually extend to your contents.
Then put the report in writing, by email or letter, so that there is a record. Say where the leak is, how long it has been happening and attach the pictures. A phone call alone leaves nothing to point to later, and a block with several affected doors tends to be dealt with once the landlord sees a pattern of reports.
Check your own cover too. A contents policy may or may not cover things stored in a garage, and our page on whether a garage roof is covered by home insurance explains what insurers look at.
Is the roof asbestos?
Lock-up garage blocks from before 2000 often have corrugated roofing that may be asbestos cement. HSE's guidance on anything built or refurbished before 2000 is to presume asbestos is there, and in a shared block that matters to everyone, because disturbing one roof affects its neighbours.
Do not drill, scrub, climb on or pressure-wash the sheets. Our page on whether your garage roof is asbestos explains how to tell.
Whoever controls a block needs to know what is on its roofs. If you are a tenant, ask the landlord whether the block has been surveyed for asbestos, and ask them to reply by email. The reply tells you whether the sheets are known or merely assumed.
Work on asbestos cement that is broken or likely to break up can be notifiable non-licensed work. That is for the contractor, not the tenant. See whether a licence is needed to remove an asbestos garage roof for the HSE position.
When owners have to organise the repair themselves
In a block where the garage owners hold the freehold jointly, or where a small residents' company owns the building, nobody else will come. The owners have to agree who arranges a repair, who collects the money and how costs are shared. A shared roof means a shared bill, and one owner cannot usually force the others to pay, but one owner can raise the issue in writing and propose a survey.
A survey is the sensible first step, because it separates a fault that can be fixed locally from a roof that needs replacing. We photograph the whole roof, the fixings, the purlins and the gutters, and the quote arrives as a single written total you can circulate to the other owners. Ask whether VAT and scaffolding are inside it.
A managing agent or a company secretary can often arrange the visit and hold the funds. If the block is under a lease, the landlord may be obliged to carry out the repair and recover the cost through the service charge, so read the lease before you start spending.
Fixing a block roof and the work involved
A shared roof is a long, low-level roof with many bays. Access is usually easy from a track at the back, but vehicles have to get through, and neighbours' cars and doors need protecting. Scaffold towers or edge protection are often needed for the work at height.
Where the sheets are intact asbestos cement and the fault is local, careful repair or replacement of the affected sheets may be enough. Where the roof is worn out, the whole run may be stripped and re-covered with a new sheet such as fibre-cement or box-profile steel, with the old sheets taken away as asbestos waste under a consignment note. Our guide on how asbestos waste is disposed of goes through the steps.
It is worth planning the job for the whole block. A neat repair to one garage next to a failing roof on its neighbour leaves the weak spots in place, and a single scheme is easier to price and cheaper in access terms.
Selling or buying a garage in a block
A buyer's solicitor will ask about the roof and the service charge, and a seller who knows the roof is asbestos or leaking should be ready to say so. The cost of a shared roof can fall on whoever owns the garage when the bill arrives. Our page on selling a house with an asbestos garage roof explains how it affects a sale.
If you want a clear idea of what is wrong before you speak to a landlord or the other owners, send photographs of the roof, the inside of your garage and any damp areas by WhatsApp, or ring 01793 626096. Our garage roof replacement page covers the wider options. Our pictures from the survey come with the written quote, a ten-year workmanship guarantee goes in writing, and we recommend only as much work as the roof needs. The old material leaves with us.