Anaerobic Digester Tank Roof Coating

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As part of the anaerobic digester tank lining project a new waterproofing membrane was required to the tank roof to protect the internal lining.


We proposed the application of a spray applied polyurea waterproofing membrane to provide a long term liquid roofing solution. Not all polyurea materials are created equal and as such we selected a grade of material specifically designed for roofing applications which can elongate in excess of 900%.

The concrete tank roof was prepared by method of vacuum controlled diamond grinding to remove surface laitance and contaminants. Regardless if the surface to be coated is a tank lining or roof coating correct preparation is the key to a long lasting polyurea coating.

Double priming the concrete tank roof

Once prepared due to the high residual moisture content of the concrete tank roof we elected to double prime using a moisture tolerant epoxy priming. Double priming ensured that when the hot spray applied polyurea membrane was applied it did not pin hole excessively, ensuring a defect free finish.

The polyurea membrane was applied using one of our four polyurea spray units applied by Polyurea Development Association trained applicators to a thickness of 2mm. Bond breaker tapes were applied over expansion joints in the tank roof to allow the movement joints to expand and contract freely below the waterproofing membrane. Once applied the coating was visually and spark tested to identify pin holes and defects.

Applying the polyurethane top coat

Finally a UV resistant polyurethane top coat was applied to ensure a consistent and lasting finish. A slip resistant rounded polymer bead was included to provide slip resistance when incidental access is required.

The finish the team achieved was particularly impressive given the amount of pipework and cabling on the roof.  Another liquid roofing job complete.