Waterproofing a Steel Roof (1)

How Waterproofing a Steel Roof Is Done

Residential Roofing Roof Roofing Repair
How Waterproofing a Steel Roof Is Done


    – Steel roofing

    – Re-sealing steel roofs in good condition

    – Re-waterproofing of steel roofs in lousy condition

    – Price of a waterproofing renovation of a steel roof

Waterproofing a steel roof can be done in several ways depending on the roof’s condition, the structure supporting it, and the objectives to be achieved. Here are a few tips to help you understand.

Steel roofing

They are very present in many places. Recognizable by the profiles of the plates, they ensure good waterproofing.

Many advantages…

Widely used for industrial buildings and later for residential buildings, steel roofing has several advantages. Usable on low slopes or flat roofs, light once in place, quick and economical to install, they have found their place in contemporary construction.

… And some disadvantages

On the other hand, single-skin steel sheets can be sensitive to pollution and condensation. Old low-quality products can show signs of deterioration due to condensation or poor resistance to bad weather, not to mention possible installation defects or corrosion defects to urban pollution.

Therefore, it is sometimes necessary to consider renovating a roof of this type by redoing the waterproofing. Different criteria must be studied to make the right choice in the technique and products of renovation. In all cases, if you are doing the work yourself, make sure that the support is solid and equip yourself with the essential personal protective equipment (PPE), such as an anti-fall harness.

Re-sealing steel tanks in good condition

Waterproofing a Steel Roof

The solutions chosen will depend mainly on the condition of the existing roof.

Defects on some plates

It is possible that the waterproofing defect is only present in a few places and is due to an assembly defect that has worsened over time. In this case, dismantling/reassembling or changing a few plates may be the best solution.

However, be careful when making these changes. It will help find panels with the same profile and overlap to last your roof. If the sheets are old and it is impossible to find similar ones to change, the following solutions are available.

Scattered waterproofing defects

You can re-seal the entire roof, but you want to keep the existing tiles. In this case, liquid waterproofing is the simplest option. These are cold-applied resins that, once dry, form a continuous, watertight film over the entire support. They can be used on their own or as an overlay to a mesh laid on the trays before covering and have the advantage of being easy and economical to apply.

You can also choose to install a membrane. The possibilities are numerous, single-layer, double-layer, mechanically fixed, welded or cold overlaps. You must discuss the best solution for you with the seller, depending on the context, the surface, the condition of the support, and your skills (if you do it yourself).

Redo the waterproofing and insulation


One solution may be to install an insulation + waterproofing complex on the existing roofing to add thermal performance to your “new” roof. It forms an over-covering whose main advantages lie in the absence of cost of dismantling the current and the possibility of continuing to occupy the premises during the work.

This system exists in sandwich plates. Thanks to a secondary metal frame, a new insulating complex + steel tank is supported and anchored in the existing steel tanks.

Redoing the waterproofing of steel tanks in poor condition

In this case, it is often preferable to consider a complete dismantling and install a new roof of compatible weight with the existing framework.

Steel decking is now available in many profiles and colours. Some designers have even worked with manufacturers to provide new ranges that add value to the buildings they equip. However, you must check with your local council to see if new steel roofing is permitted in your area.

Finally, the price of a waterproofing renovation depends, of course, on the chosen technique and the roofing surface, from a simple self-made waterproofing to a roof made of sandwich plates by a professional.

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