Watford Office Roof Waterproofing
An office roof in Watford was refurbished with Impermax over an existing PVC membrane.
Overview
An office roof in Watford was refurbished with Impermax over an existing PVC membrane.
| Place | Watford, United Kingdom |
|---|---|
| Work | Roof refurbishment over PVC |
| Membrane | Impermax |
Challenge
A PVC membrane that has aged is a smooth, often chalky surface. Water gets in at the laps and at punctures. Covering it with Impermax only works if that surface is clean and the liquid can hold. A dirty PVC membrane lets the new film peel on the first hot afternoon.
Watford, the PVC membrane and Impermax are the job. The new film is only as good as the clean overlap onto the old laps and the outlets.
Solution
Impermax is Krypton Chemical’s cold-applied liquid polyurethane membrane. It goes on by roller, brush, spreader or airless equipment, in two coats of about 1 kg per square metre each. The coats are different colours, so a missed patch shows while the work is still open. A spiked roller is run while the coat is wet, to break bubbles before they set. A mesh is not required across the field. It is used at edges and corners, the places a liquid film is asked to turn.
Elongation is 450 to 600 percent and tensile strength is 2.5 to 4.3 MPa. Those figures are typical product data, measured on the product under stated conditions. They are not a cut taken from this job. On a surface that moves with heat, that elongation is why the film can stay with the substrate instead of cracking where the plane changes.
The substrate wants to be between 5 and 40 degrees C. Above 45 degrees C the work needs extra measures. Pot life is about 4 to 6 hours for 1 kg at 20 degrees C and 50 percent relative humidity. People can usually walk the film in one or two days. It reaches about 90 percent of its properties in three days. Final hardness takes 10 to 15 days, and standing water should wait for that. The European Technical Assessment is 06/0263, with CE marking for the 10-year and 25-year working-life categories. The system also carries a BBA agrément.
The two colour coats show whether the overlap onto upstands and outlets is real. Over an old PVC membrane, those are the lines that were already the weak ones. Cold application means the refurbishment does not torch a membrane that can be damaged by heat.
Application
Stir the pail slowly so settled solids come back and bubbles can leave. Do not thin it with a solvent that is not the Rayston PU solvent. The surface is cleaned, cracks and weak spots are dealt with first, then the two coats go down, including upstands and outlets in the same passes. Details are not left for a leftover tin at the end of the day.
On this job the same rule applies at every edge. the new film has to hold onto a PVC membrane that is already there, not onto fresh concrete. A holiday in the second coat is a path. The colour change is how that path is seen before the surface is handed back. Outlets, upstands and fixings take the same two coats as the field, because water does not fail in the middle of a bay. It fails where the plane changes.
Results
The Watford office roof has an Impermax liquid membrane over the existing PVC, with the details in the same coats as the field.
Products
Impermax
Cold-applied liquid polyurethane. Two coats at about 1 kg per square metre each. Elongation 450 to 600 percent. Those figures are typical product data.
FAQ
How is Impermax applied?
By roller, brush, spreader or airless equipment, in two coats of about 1 kg per square metre each. The coats are different colours so a holiday shows. On this roof that matters because the new film has to hold onto a PVC membrane that is already there, not onto fresh concrete.
How long before the film can be walked?
Usually one or two days. About 90 percent of the properties are there in three days. Final hardness takes 10 to 15 days, and standing water should wait for that. On this roof a film that is walked or flooded early is still soft.
What temperature does the substrate need?
Between 5 and 40 degrees C. Above 45 degrees C the work needs extra measures. A surface in full sun can pass that even when the air feels moderate, and this roof is no exception.
What do the strength figures mean here?
Elongation is 450 to 600 percent and tensile strength is 2.5 to 4.3 MPa. Those are typical product data, not a test cut from this job. They are why the film can follow movement at upstands and outlets on this roof.
Where do the cure times come from?
From the Impermax technical data sheet, measured on the product under stated conditions. They are not a stopwatch reading from this roof. The ETA for the system is 06/0263.