Roof structures

Roof types

316 Stainless steel digester

At the highest end of roof design, the 316 stainless steel skin option is an external beam construction where the roof plates are located below the beams.

This solution is most commonly used in the AD market as gas tight roofs for steel digester tanks operating under pressure, both positive and negative.

This roof is supplied with a 316 stainless steel skin to provide the most robust solution when in contact with the gas space of digester tanks ensuring longevity and a maintenance-free structure.



Balmoral Tanks’ aluminium roof is an excellent solution, particularly for export projects, given the lightweight properties of aluminium alloy.

The roof construction is essentially a central gantry that spans the tank walls, allowing the roof to self-support across a range of diameters. The roof is not dependent on coatings for the corrosion protection, which again, is a great feature of this roof.

Used extensively for applications such as demineralised water storage, the aluminium roof can make a significant difference in challenging specifications.


Coated steel plate

Balmoral’s coated steel roof comprises of efusion® epoxy coated roof panels supported on top of a full epoxy coated sub-structure.

Offering a fully coated roof structure, the roof is protected against corrosion in every way. This roof can be fully sealed and designed for low pressure applications, so if the contents need to be fully protected, this roof will suit the specification.

A low profile solution, generally at five-degree pitch, but can be designed for higher load scenarios when, for example, permanent personnel access is required.


Double membrane gas holder

This option is well established in the AD market, offering a low cost option to a sealed, gas tight roof.

Operating with the inner membrane column supported as the gas collection zone, the outer membrane remains permanently inflated so the inner can fill and empty in line with on-site gas production.

This type of roof will never meet the design parameters of a stainless steel digester roof in areas such as pressure but if you are operating with a low pressure rating then this option is worth considering.


Glass reinforced plastic (GRP)

Very similar solution to a coated steel plate roof but provided in a glass reinforced plastic (GRP) material.

This material provides high resistance to corrosion and is generally supplied as either 20-degree pitch or low profile beam and infill solutions. GRP roofs can be sealed, although not gas tight, and manufactured to WRAS standards, meaning suitability for clean water and drinking applications.


Single membrane

In some respects, a very similar roof to the trough deck system, in so much as it is suitable for low tech applications, such as debris roofs.

Offering a centre column supported fabric roof fixed back to the tank walls. These roofs have been used widely in the agricultural market but have been specified in the water treatment markets.

The single membrane roof can be used for odour control applications so is one to consider if you are looking for tight control on cost while maintaining performance.


Trough deck

Ideally suited for use as a debris roof. This is a low profile roof that is used in low tech applications, such as golf courses or water irrigation.

The roof can be supplied with a fully epoxy coated sub-structure to further enhance its performance capability. If you want to keep it simple, this could be the option for you.


Balmoral Tanks roof structures