Roof membrane: how to choose the best one (5 things to check)

There are now many floating roof membranes on the Danish market, and they look similar on the shelf. The difference only becomes apparent after a few winters. Here are the five things you should look for before choosing, and how Luna Roof compares to each of them.

1. Elasticity: can the membrane follow the roof?

A roof works. It expands in the summer heat and contracts in the frost, and the substrate moves with it. A membrane that cannot stretch will crack instead.

Look for the elasticity percentage, and keep the number up against Luna Roofs up to 300%. The more the membrane can stretch, the better it bridges cracks in the substrate instead of snapping over them.

2. Seamless or with seams?

Almost all leaks start in the same place: in a joint. In the case of roofing felt, it is the overlays, in the case of sheets, it is the screw holes and flashings.

A liquid membrane is applied as a liquid and cures into one continuous surface. There are no joints because there are no edges to join. This is the single biggest difference between liquid membrane and traditional roofing felt.

3. Lifetime and warranty are not the same thing

Many manufacturers state an expected lifespan, but far fewer sign a warranty. Always ask what is actually covered and for how long.

Luna Roof has an expected lifespan of up to 40 years and a 25-year product warranty. The warranty is on the product, not just on whether the bucket was full when you opened it.

4. Temperature range

A flat roof in Denmark must be able to withstand both frost in winter and a sunny summer day with a black coating, without the membrane becoming brittle or sticky.

Luna Roof has been tested from -40 °C to +90 °C. This number is the operating temperature, i.e. what the membrane can withstand year after year when it is cured.

5. Can you apply it yourself?

This is often the real price difference. If the membrane requires a gas burner, multi-stage primer, or a licensed installer, the labor costs end up costing more than the material.

Luna Roof is 1-component and ready-mixed. It is applied with a roller or brush, and one coat is enough. 20 kg covers up to 13.3 m², i.e. approx. 1.5 kg per m².

How to calculate the price

Always compare per square meter, not per bucket. Buckets have different sizes and different consumption, so the price per liter alone means nothing.

The calculation is: price per bucket divided by the number of m² the bucket covers. On our product pages you can enter the size of the roof and get the number of buckets immediately.

How about a brand new roof?

A full roof replacement costs many times more than a seal, when demolition, disposal and labor are factored in. Sealing with a membrane can be done in a few days without tearing anything down.

The prerequisite is that the existing structure is sound. If there is rot in the rafters or water in the insulation, this must be fixed first. The membrane solves the leak, not moisture damage that is already present in the structure.

Briefly summarized

• The elasticity is expressed in percentage, and the higher the better.
• Seamless surface without overlays
• Written product warranty, not just an expected lifespan
• Temperature range covering Danish winter and summer
• Application you can do yourself if you want to save on labor costs