Liquid Gutter Lining

Technical Defect Analysis

Defect Category: Gutters & Rainwater Management
Roof Element: Internal Gutters / Valley Gutters

What This Defect Is

Liquid gutter liners are used to refurbish internal and valley gutters on industrial roofs
where joints, laps and localised corrosion are allowing water to escape.

Over time, gutters can suffer from standing water, joint movement and mechanical damage.
Historical patch repairs can also be problematic, particularly if they have not been carried out with care and attention.

Where the substrate is still structurally sound, a correctly
specified liquid gutter lining system can provide a continuous, fully bonded waterproof
lining, avoiding the need for wholesale gutter replacement.

Problems typically arise when paint-type coatings or general roof coatings are used in
gutters instead of a purpose-designed liquid liner. These products are often not suitable
for permanent immersion, do not cope well with joint movement and can fail prematurely,
leaving the underlying gutter in a worse condition.

Causes

• Long-term standing water due to poor falls or ponding around outlets.
• Thermal movement at gutter joints and connection details.
• Corrosion at bolt holes, end joints and stop-ends.
• Historic bitumen, mastic or fibre-reinforced patch repairs.
• Incompatible or poorly adhered legacy coatings in the gutter.
• Blockages from debris, leaf build-up and neglected maintenance.
• Overspill from defective roof sheets or rooflights discharging into the gutter.

How to Identify

• Staining and damp visible below gutters or at internal junctions and columns.
• Active drips at gutter joints, outlets or sumps during or after rainfall.
• Ponding water that remains in the gutter 24–48 hours after rain.
• Corrosion, pitting or perforation visible along the gutter bed and sides.
• Cracked, crazed or debonding legacy coatings and local patch repairs.
• Daylight visible through joints, bolt holes or previously treated areas.

Risks if Untreated

• Progressive corrosion of the gutter substrate and associated support steelwork.
• Water ingress causing damage to ceilings, finishes, stock and equipment.
• Slip hazards caused by moss or vegetation growth in the working areas below, leading to health & safety risks.
• Increased remediation costs once perforation and structural deterioration occur.
• Potential business interruption and tenant / landlord disputes on dilapidations.

Condition Ratings

Early

Localised coating breakdown and light surface rust at joints, but no perforation.
Ponding is present but the gutter still appears structurally sound.

Moderate

More extensive visible rusting along joints and bolt lines, with
evidence of intermittent leaks. Some historic patch repairs present.

Poor

Widespread corrosion, multiple leaking joints, failed or debonding legacy coatings, and
areas of significant pitting. Gutter may hold water for prolonged periods.

Severe

Advanced corrosion with perforations, deformation of the gutter bed or sides, and
repeated failures of previous repairs. In these cases, partial or full gutter
replacement should be considered and a liquid liner may no longer be appropriate.

Recommended Treatment

Before specifying a liquid gutter liner, confirm that the gutter is structurally sound
and capable of providing adequate support to a new lining system. Address any issues
with falls, outlets or significant substrate failure as part of the overall scheme.

Where liquid lining is appropriate, a purpose-designed liquid gutter lining system,
such as Liquasil’s three-component Gutterseal system, should be specified.
This includes corrosion control, joint reinforcement and a fully bonded waterproof
liner suitable for permanent immersion.

• Thoroughly clean the gutter to remove silt, debris, loose coatings and contaminants.
• Mechanically prepare corroded areas to a bright metal finish in accordance with
  ST3 standard (bare, non-shiny steel).
• Prime prepared metal and corroded areas with Liquasil SWT Corrosion Primer
  in accordance with the manufacturer’s instructions.
• Seal joints, bolt heads, seams etc., usingLiquasil Non-Sag Sealer to create a stable, flexible detail.
• Apply Liquasil One, as part of the Gutterseal system, as a continuous liquid
  gutter liner over the entire gutter, including areas coated with Non-Sag Sealer, including sides, sumps, outlets and stop-ends.
• Install at the specified wet film thickness of 750-1000microns to create a fully bonded, durable liner capable of withstanding permanent standing water and thermal movement.

Specification Wording

“Clean existing internal gutters to remove all loose coatings, debris and contaminants.
Mechanically prepare corroded areas to ST3 standard (bare, non-shiny metal) and ensure
the substrate is dry, sound and suitably profiled. Prime all areas of exposed metal
and joint locations with Liquasil SWT Corrosion Primer in accordance with the
manufacturer’s instructions. Seal joints, bolt heads, outlets and localised
defects with Liquasil Non-Sag Sealer to form a stable, flexible detail. Apply
Liquasil One as a fully bonded liquid gutter liner to the gutter base, sides, sumps,
outlets and stop-ends as part of the Liquasil Gutterseal liquid gutter lining system,
installed to the specified minimum wet film thickness of 750-1000 microns to provide a continuous,
seamless gutter lining.”

Additional Options

• Adjust or re-form falls where practical to reduce excessive ponding.
• Upgrade or increase the number of outlets and overflows to increase discharge capacity and improve resilience.
• If not already present, consider the addition of weirs at the stop end to prevent overflow into the building
• Replace severely corroded gutter sections prior to installation of the liquid liner.
• Introduce regular maintenance and cleaning regimes to prevent future blockages.

Suitable Liquasil Products

• Liquasil SWT Primer – corrosion primer for prepared metal substrates.
• Liquasil Non-Sag Sealer – thixotropic joint and perforation sealer.
• Liquasil One – liquid gutter liner forming the full-area waterproof lining.
• Liquasil Surface Degreaser – for degreasing contaminated metal surfaces.

FAQs

When is a liquid gutter liner appropriate?

A liquid gutter liner is appropriate when the gutter is still structurally sound but
suffers from joint failures, localised corrosion or poor quality, historic patch repairs. Where
there is advanced deformation, widespread perforation or serious structural damage,
replacement or part replacement should be considered instead.

Can any roof coating be used as a gutter liner?

No. Many roof coatings are not designed for permanent water immersion or joint
movement. Using a general roof coating in a gutter often leads to premature failure.
A purpose-designed liquid gutter lining system, such as Gutterseal, should be
specified for gutters.

Do gutters need to be completely dry before installation?

The substrate must be dry and free from standing water at the point of installation,
otherwise adhesion and cure will be compromised. Local drying and temporary diversion
of water may be needed so that primers, jointing materials and the liquid liner can
be applied under suitable conditions.

How Can I Arrange An Industrial Gutter Survey?

Liquasil’s team can assist professional specifiers considering a liquid gutter liner free of charge. If you require
professional advice from a fully insured industrial roofing specialist, please visit RoofSurveys.com.

Contact Us

We are happy to provide one-to-one guidance and assistance to professional specifiers.
Call us on 0121 709 5352 or use the contact form on this website to send your survey
images for review.