How To Waterproof Stepoc Block Walls

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How to waterproof stepoc block walls.

Ensuring success when waterproofing stepoc block retaining walls. Using the correct systems is key.

What are stepoc block walls?

Stepoc block walls are hollow blocks that are then filled with concrete. They are often used for retaining wall construction as they are cost effective and strong and do not require expensive rebar or formwork like site poured reinforced concrete walls.

Waterproofing of new build basement walls- stepoc block.

In order to prevent water ingress into a basement it is important to use an effective waterproofing system.

Stepoc block walls will require a “post applied system” this means that the waterproofing is applied to the wall – after it has been built.

There are two types of post applied waterproofing systems- Fully bonded, liquid applied such as Koster Deuxan 2c or self adhesive such as Koster KSK.

Of the two systems we find the fully bonded liquid applied Deuxan 2c to be more reliable.

Note that you can’t use waterproof concrete for stepoc block walls. The structure of the blocks creates pathways for water to bypass the waterproof concrete

1- Access-

Good access is required to the outside of the stepoc block wall to allow for the application of the waterproofing. Remember the wall will be built and you will need space to accurately and carefully apply the waterproofing

2- Surface preparation.

The stepoc block wall should be thoroughly cleaned to remove surface contamination before the waterproofing is applied.

3 – Pre treatment. 

Some building materials, such as new concrete, can generate free lime which could damage the tanking layer. This free lime should be encapsulated using a free lime blocker such as Koster Polysil TG500

4- Internal Angles.

Right angles in the structure can create problems for waterproofing systems. Koster Repair Mortar Plus can be use to form rounded fillets at internal angles. These fillets can spread the loading of any water pressure and remove any pinch points.

5- Applying the waterproofing.

Koster Deuxan 2c is a two part thick film sealant. Deuxan 2c is applied in two coats to the outside surface of the stepoc block wall. Deuxan 2c can be hand applied with a trowell or, for larger areas, spray applied using a peristaltic pump.

6- Backfill Protection.

It is likely that the walls will be backfilled against. This means it is a good idea to protect the waterproofing from damage. Delta Geodrain Quattro offers great protection against impact damage and also improves the external drainage around the structure to reduce the pressure on the waterproofing layer.

7- Internal Systems. 

Often for new build residential projects it will be necessary to provide a secondary waterproofing system internally in order to meet the requirements of a structural warranty provider. We will be happy to advise on this for your project.

Need help in selecting or installing the right waterproofing system?

Let us know our team of waterproofing experts will be happy to help.