Applying Impermax to an existing roof covering? Here’s how to do it safely!

An existing roof covering doesn’t always need to be completely replaced to provide years more protection. With Impermax, a liquid roof coating based on polyurethane, you can apply a seamless, waterproof layer that makes the roof look like new again. However, applying Impermax requires the right preparation, materials and safety measures. In this article we explain, step by step, how to apply Impermax over an existing roof covering for roof repair — and, most importantly, how to do so safely.

Can I use Impermax over my existing roof covering?

Yes. Impermax is specifically designed to be applied over existing roof coverings, provided the substrate is stable, clean, dry and compatible. Typical substrates include bitumen, EPDM, concrete or timber. Before you start, however, there are a few essential steps to avoid mistakes.

Step 1. Inspect the existing roof layer carefully

Check that the existing layer is still firmly bonded and free from blisters, cracks or loose areas. If not, you must repair or remove these first. Impermax will not adhere properly to unstable or damaged surfaces. Use a moisture meter if you have any doubts about moisture beneath the layer.

Step 2. Clean and dry the roof thoroughly

Remove dirt, moss, dust, oil, loose gravel or debris. Use a pressure washer if necessary. Allow the roof to dry completely afterwards — including under eaves and in shaded areas. Moisture is the biggest enemy of good adhesion.

Step 3. Choose the correct primer for your substrate

Impermax has specific primers for different substrates. Bitumen requires a different primer than EPDM or concrete. Without the correct primer you risk delamination or blistering. If in doubt, seek advice.

Step 4. Repair cracks and vulnerable details

First repair all seams, joints and cracks in the existing layer. Use reinforcement fleece (such as polyester fleece) on upstands, corners and edges — these areas are particularly prone to leaks.

Step 5. Apply Impermax in several thin coats

For renovation projects it is crucial to apply Impermax in several thin coats. Thick coats can trap air or cure poorly. Allow each coat to dry completely before applying the next. Work with a suitable roller or brush.

Preparation is crucial when renovating with Impermax

Applying Impermax over an existing roof covering is a smart and sustainable way to refurbish your roof. The key to success, however, is thorough preparation. Inspect your roof carefully, use the correct primer and apply neat, even coats. That way you avoid problems and extend the life of your roof.