What Consultants Check in a Waterproofing Injection Method Statement

On managed buildings and projects, injection work does not start until a consultant or the facilities engineer has approved the method statement. A weak statement comes back with comments, and the job slips by a week. These are the six things reviewers look for, and what a good statement contains for each.

1. Is there a diagnosis, or only a generic scope?

"Inject all cracks as required" is a common reason for a statement to be returned. Reviewers expect the defects to be identified before the method is chosen:

• Each leak location numbered and marked on a layout, with photographs.
• The type of defect: crack, construction joint, pipe penetration or honeycombed concrete.
• Whether it is active (flowing or damp) or dry, and approximate crack widths.
• The likely source: groundwater, water coming down from a deck above, or a plumbing fault that needs a plumber first.

2. Do the products match the defect, with the data to prove it?

• Named products, each with its technical data sheet and safety data sheet attached.
• The EN 1504-5 class of the permanent resin. EN 1504-5 is the European standard for concrete injection products. It classifies them by use: F for force-transmitting filling, D for ductile (flexible) filling, S for swelling filling. A leaking crack that still moves needs a flexible product, while a crack that has to carry load again needs a force-transmitting one, usually epoxy. The class on the data sheet should match the defect.
• The role of each product. Where water is flowing, a water-reactive foam stops it first. That foam is a temporary stage, and the statement should say which resin provides the permanent seal.
• Potable-water suitability for anything used in a drinking-water tank, stated on the data sheet.
• Storage and temperature limits. Resins react faster in Abu Dhabi heat. The statement should show how materials are kept within the temperatures on the data sheet.

3. Are the sequence and parameters defined?

The method should be specific enough that a reviewer can check it on site:

1. Surface preparation and marking of the crack line.
2. The drilling pattern: holes drilled at an angle to cross the crack inside the concrete, alternating either side, at a stated spacing.
3. Flushing the holes and fixing the packers.
4. The injection order, for example from the lowest packer upwards, and when to move on: typically when resin appears at the next packer or at the surface.
5. Injection pressure kept within the manufacturer's limits.
6. Curing time, then packer removal and filling of the holes with repair mortar.

Where the manufacturer publishes its own method statement for the product, the contractor's statement should follow it and say so.

4. Is there an inspection and test plan with hold points?

The method statement says how the work is done. The inspection and test plan says what is checked, when, by whom and against which criterion. Typical hold points for injection work:

• The leak list and layout agreed with the consultant or FM engineer before drilling.
• Packer installation on a sample length, where the reviewer wants to see it.
• The post-cure inspection of every treated location.

The acceptance criterion should be written down, for example "no visible seepage at the treated location at the post-cure inspection", together with what happens if a location fails: re-injection and a second inspection.

5. Does the safety section fit the work?

• Chemical handling. Polyurethane resins contain isocyanates. Gloves, eye protection and ventilation should follow the safety data sheet.
• Confined spaces. Tanks, sump pits and lift pits need entry permits, gas testing, ventilation and an attendant.
• Electrical isolation where water and drilling are near cables, panels or pumps.
• The building's own rules: permit-to-work, working hours for noisy drilling, barriers and signage in occupied areas, and protection of cars and finishes.
• Waste. Disposal of empty resin containers and cleaning solvents.

6. Who is responsible on site?

A named supervisor, and evidence that the crew is trained in the product system. Manufacturer method statements for injection resins say personnel should hold a current certificate of competence from the supplier, so reviewers increasingly ask for it. The statement should also say who issues the warranty, in writing, and what it covers. Manufacturers warrant the product, not the installation. More on this in how to choose a waterproofing contractor.

What happens after approval?

The approved statement becomes the checklist for the work and the structure of the completion report: each numbered location, the product used, the hold-point records and before-and-after photographs. On car parks and tanks, the statement also carries the phasing plan. See car park leak repair without closure and building water tank repair.

For the documents we submit to facility managers and consultants, see leak repair for managed buildings.