Concrete Guttering Installation Guide

Concrete gutters, commonly known as Finlock gutters, were a popular architectural choice in the UK between the 1950s and 1970s. Unlike modern uPVC systems, these are structural blocks that sit atop your cavity walls, serving as both a gutter and a lintel for your windows.

While they were built to last, many British homeowners now face issues with "cold bridging," damp, and internal leaks. Whether you are looking to reline your existing concrete gutters or replace them entirely with a modern uPVC equivalent, understanding the technical requirements is essential for protecting your home’s structural integrity.

What Does the Work Involve?

• Structural Survey: A specialist will assess the condition of the concrete blocks, looking for cracks, sagging, or signs of "blown" masonry.
• Surface Preparation: Existing debris, old bitumen, or failed liners are removed, and the concrete trough is cleaned to ensure a smooth substrate.
• Lining Installation: If repairing, a high-performance EPDM (rubber) or liquid membrane liner is bonded to the concrete to create a seamless, waterproof seal.
• Removal (Optional): For full replacements, the protruding "nose" of the concrete block is cut away using diamond-tipped saws to allow for a standard fascia and uPVC gutter setup.
• Downpipe Integration: Ensuring the existing drainage holes are correctly sleeved and connected to new or existing downpipes to prevent water entering the cavity.
• Final Testing: The system is water-tested to ensure the "fall" (the slope) is sufficient for water to reach the outlets without pooling.

Typical Costs

The cost of concrete gutter work depends heavily on whether you choose to reline the existing troughs or remove the concrete "nose" to fit modern uPVC. Prices below include VAT and standard labour rates for 2025/26.

Factors affecting the final price include the height of the property, the total linear meterage, and whether the concrete has caused structural damage to the window lintels below, which may require additional masonry work.

How Long Does It Take?

• Minor Repairs/Patching: 2–4 hours.
• Full Relining (Semi-Detached): 1–2 days.
• Concrete Removal and uPVC Installation: 2–4 days depending on the size of the property.
• Scaffolding Setup/Striking: Usually 1 day before and 1 day after the actual works.

DIY or Professional?

Working on concrete gutters is strictly a professional task. These gutters are incredibly heavy and form part of the building's structure; improper cutting or drilling can lead to lintel failure or collapsed masonry. Furthermore, working at height requires specialist access equipment that meets UK Health and Safety standards. A DIY failure in this area often results in internal damp that can cost thousands to rectify.

Note: If your property was built before 1990, the old bitumen sealants or internal coatings may contain asbestos. A professional will know how to identify and handle this safely.

Choosing the Right Tradesperson

• Specialist Experience: Ask specifically if they have worked with Finlock/Concrete gutters before; general roofers may not have the specific tools for concrete cutting.
• Insurance: Ensure they hold Public Liability Insurance (minimum £2 million) and are covered for "hot works" if they use heat-applied membranes.
• References: Ask for addresses of local jobs completed at least two years ago to see how the liners have held up.
• Questions to Ask:
  • Do you provide a guarantee (typically 10–20 years for lining)?
  • How do you handle the "cold bridging" issue if I choose relining?
  • Is scaffolding included in your quote, or is that a separate contract?

UK Regulations

• Work at Height Regulations (2005): Contractors must use appropriate edge protection or scaffolding; ladders are rarely sufficient for full gutter replacements.
• Building Regulations (Part L): If you are removing the concrete gutters, you must ensure the replacement system does not compromise the thermal performance of the wall-to-roof junction.
• Asbestos Regulations: Any suspected asbestos-containing materials (ACMs) in old sealants must be handled according to HSE guidelines.

Common Problems

• Cold Bridging: Because the concrete block spans from the outside to the inside, it conducts cold into the house, causing a line of black mould on the ceiling inside.
• Sagging Blocks: Over time, the heavy concrete can sag over window openings, making windows difficult to open or causing glass to crack.
• Expansion/Contraction: Concrete and metal liners expand at different rates, often causing "seamless" liners to pull away at the joints.
• Improper Falls: If the house has settled, the gutters may no longer slope toward the downpipe, leading to standing water and accelerated decay.

Frequently Asked Questions

Why is there mould on my bedroom ceiling near the window?

This is likely due to "cold bridging." The concrete gutter block acts as a thermal bridge, bringing the cold outside temperature into your warm room. Moisture in the air condenses on this cold strip, leading to mould growth.

Can I just paint the inside of the gutter with bitumen?

Bitumen is a temporary fix and often fails within 12 months due to UV degradation and thermal movement. A professional EPDM liner or liquid membrane is a far more durable solution.

Is it better to reline or remove concrete gutters?

Relining is cheaper and less disruptive, but it doesn't solve the "cold bridging" mould issue. Removal and replacement with uPVC is more expensive but provides a permanent solution to both leaks and thermal issues.

Do I need my neighbour's permission?

If you live in a semi-detached or terraced house, your concrete gutters are likely shared. You must inform your neighbour, especially if you are cutting the concrete, as a "stop-end" will need to be installed at the boundary line.

How long do relined gutters last?

A professionally installed EPDM or high-quality liquid membrane liner typically lasts between 20 and 25 years, provided the underlying concrete remains structurally sound.