The short answer
Often, yes. A Finlock gutter is a concrete channel built into the eaves of some 1950s houses, and the usual fault is leaking joints between its sections. A lining laid inside the channel can seal it. Linings do not suit every gutter, and they can fail in turn. RICS advice is that removal should not be assumed.
How a lining works in a concrete Finlock gutter, where it falls short, and how to tell whether lining or removal suits your house.
What a Finlock gutter is and why it leaks
A Finlock gutter is a concrete eaves gutter made from precast sections that interlock and sit on the wall. RICS shows one on a 1950s local authority house, and the form turned up on some homes built in that decade. A section of concrete is far heavier than a plastic gutter, and it is built into the structure, not hung from a bracket.
The weakness is at the joints. In the RICS defects record, leaks at the joints are blamed for serious decay in many cases, which gave the construction a poor name. Water that gets through runs into the wall, the lintel above the windows and the roof edge, and it does so slowly enough that the damage can go unseen for a long time. It also says a close inspection can show which gutters really need replacing and which will carry on perfectly well if looked after.
Not every house on an estate has them, and the age of a street does not tell you for certain. A pair of semis can differ from the pair next door if one was altered, so look at your own eaves rather than reasoning from the road. If you see a deep concrete channel at the eaves, with no fascia board in front, you may have one. Our blog post on replacing concrete Finlock gutters gives the wider background.
How lining works
A lining is a new waterproof skin laid inside the concrete channel, so that the water runs along the lining and not through the joints. The RICS record describes a gutter once lined with profiled stainless steel to stop leaks at the section joints. Other systems use flexible sheet membranes or liquid-applied coatings laid inside the trough. The surface has to be cleaned and repaired first, and the outlets and ends detailed with care.
The advantage is that the structure stays in place, which also keeps the look of the house exactly as it was. There is no demolition of the eaves, no new support and less disturbance to the roof edge and the wall. For a concrete gutter whose body is sound and whose only fault is the joints, lining can be the practical answer.
A lining follows the existing falls. The channel must drain to its outlet, and a lining cannot fix a gutter that holds water. We check the fall on the survey and look at how the lining will end at each outlet. Our page on gutter fall per metre explains why.
How long it lasts and where it falls short
How long a lining lasts varies with the system, how well the base was prepared and what the house does to it, and a guarantee is no promise of life. RICS makes it plain that linings fail too: its example is a gutter whose stainless steel lining now needs renewing in turn.
A lining does not cure everything. If the concrete is cracked or spalling, or the steel reinforcement inside has rusted and expanded, the lining sits on a failing base. RICS also notes that concrete poured into the inner sections can end up working as the lintel above upstairs windows, and a leak puts that at risk. A lining can cover up trouble there, so the structure gets a proper look first.
RICS warns against assuming a gutter must come out, and we agree. Lining suits a sound channel with leaking joints. If the structure has gone, a close inspection and photos should show it, and the written price will say which route we recommend.
When removal is the better route
Removal makes sense when the concrete is broken, the reinforcement has rusted through, or the gutter is part of a lintel that has deteriorated. It is also worth considering when the roof edge is being rebuilt anyway, because a re-roof gives access to the eaves. Taking out the old sections and fitting a new gutter on a fascia or a proper support gives a house a conventional system.
It is a bigger job. Heavy sections come off in pieces, the wall and the roof edge are made good, and the roof edge and gutter are re-formed together. That calls for scaffold and, on a house with a large roof, careful sequencing so the building is never left open to rain overnight.
The sensible step is a survey. Send the address, the age of the house and some ground-level photos of the gutter and the wall under it. We look at the joints, the fall and the state of the concrete, then put the route that fits your gutter into a single written price. Our box gutter lining answer covers a similar idea on commercial roofs, and our gutters, soffits and fascias page covers the wider range.
More on this in Gutters, Soffits & Fascias in Crawley
Two more Finlock gutter questions
Do all Finlock gutters need replacing?
No. RICS cautions against assuming removal, and says a close inspection shows which gutters need major work and which stay sound with sensible care. The joints, the fall and the concrete decide it, so the answer comes from examining your own gutter on site.
Does a lined Finlock gutter need maintenance?
Yes. Keep the outlets clear, check the lining at the joints and ends when you clear the gutter, and watch for damp on the wall beneath. A lining that has failed needs replacing, as the RICS record shows, so catching a fault early keeps the repair small and the wall dry.