Finlock gutters were commonly used during the 1960s and are very much of their time and in most cases are now past their time as well. The gutter system was intended to be a combined cavity closer, lintel and gutter system to speed up and simplify construction. The system comprises an integrated concrete gutter, lintel and eaves product that is fitted in sections which are typically 200mm to 250mm width, incorporating a cavity closure at their head.
Common problems include –
- An inadequate number of outlets which causes flooding and leakage.
- Gutters have often been lined or sealed with an asphalt or similar liquid applied product – older repairs have very often not only failed but worsened the problem as the finish is crude and uneven and the channel size has been reduced and so has capacity.
- Gutters are generally laid level and are consequently extremely liable to blockage and flooding, over time the sections settle and become misaligned making this situation worse.
- As sections settle the joints open up and can start to leak, this leakage can become apparent on the inside of the building.
Condensation and dampness becomes evident internally, typically to the upper 200mm or so of the wall. This develops as a result of a ‘cold bridge’. Quite often Finlock gutters were used above cavity walls which were insulated or had better thermal performance. The concrete gutter is solid from outside to inside and so when it is cold outside the concrete sections are colder inside than the adjacent surfaces and so attract condensation when environmental conditions are right. This can often be seen as a line of black mould just below the ceiling.
Repair can be carried out, essentially it is a choice between lining the gutter or cutting away the protruding section of gutter and fixing a more traditional fascia board and gutter. Both methods have their benefits and will work, on balance we prefer to see them cut away rather than lined because that helps to relieve the condensation problem.