When should I put the waterproof coating on my new concrete?

Published 14 Dec 2017

2 mins read

Updated 29th November 2023

Concrete has a complicated relationship with water – on the one hand it serves as a key ingredient, triggering the chemical reaction that causes the concrete to harden. But despite being essential to the creation of concrete, water can also quickly damage concrete after it has set.

As concrete hardens, pockets of air form within the slab. Most of these bubble to the top, but many stay within the slab, making it semi-porous. Once the slab has fully hardened these air pockets allow moisture to penetrate the slab, where it can damage the concrete in the following ways:

  • When the water expands and contracts in different temperatures it can crack the concrete
  • The moisture can encourage fungal growth
  • The metal within reinforced concrete can rust, which can crack the concrete from within

For these reasons it’s important to waterproof any concrete that might come into contact with moisture. The most common method of doing so is to add a protective layer of waterproofing once the slab is set. But when exactly should this coating be applied?

Concrete continues to cure long after the concrete is poured. This curing process will expel water vapour and air for days after the concrete appears to be set. Sydney waterproofing companies will generally advise a waiting period of at least 7 days from pouring before a waterproof coating is applied. If the coating is applied earlier there is a risk of escaping air bubbles and moisture preventing the waterproof coating from bonding with the concrete.

This waiting period will change depending on the waterproofer used. Some liquid membranes may need to be applied 14 days or longer after the concrete is poured. Others might be able to be applied sooner. The waterproofing option that you choose should come with a recommended waiting period, so always stick to the manufacturer’s instructions.

Alternatively, you can simply leave the job to our waterproofing professionals who’ll ensure that the job is done right. Contact us for waterproofing solutions in Sydney.

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