Including a sub-grade basement in construction maximises available land space. A sub-grade basement can provide more stable construction, is thermally efficient and offers ideal quiet areas and further space for storage or accommodation. Basements can be economically introduced onto most sites and, in particular, have clear advantages on sites with poor ground that may otherwise be regarded as difficult and possibly uneconomic to build on.

Nuralite has been supplying waterproofing solutions including flat roofing and sub-grade tanking for the last 50 years. Here are a few things they have learnt.

Tanking considerations:

Site Conditions

During initial ground works, the site is never clean and 100% dry. Some tanking products rely on adhesives or chemical bonds that can be easily rendered useless when contaminated with dirt / mud and wet conditions. It is possible to have a window of optimum conditions, but it is highly likely in our subtropical climate that rain is not too far away. Nuraply 3PT is not affected by contact with water and will not swell or wash out. The heat welding of laps ensures a watertight connection.

Economical

It is very difficult to persuade a person to pay a premium for something that is going to be buried. Some may claim that a plastic sheet is the most economical option, but keep in mind that this discussion is on sub-grade tanking, not damp proofing. Nuraply 3PT provides a warranted waterproof system to the sub-grade area.

Tough

Unlike a roofing application where once the roof is on, trade traffic is limited, once the tanking is installed, structural steel is then placed within the floor slab area and is subject to very heavy foot traffic and possibly even vehicle traffic. Nuraply 3PT is a 3mm thick, polymer modified bitumen membrane incorporating a strong 180gsm non-woven polyester reinforcement. If for some reason the membrane is damaged, it is very easy to repair by torch welding a patch over the damaged area.

Speed

Typically very little construction can take place until the ground works and floor slab have been done. Speed of installation is critical. Nuraply 3PT can be loose laid flat in an under slab situation at approximately 600m² per day per two man team. Once laid there is no further curing or reaction time. Backfilling or placement of flooring slab can commence immediately after installation.

Detailing

It is very common for pipes etc. to penetrate the floor slab, thus, also penetrating the tanking membrane. Some tanking products rely on a simple pressure tape to hold the split membrane in place. The Nuraply 3PT product is fully torch welded to form a watertight seal. The same principle can be applied to repairs of the Nuraply 3PT membrane system; as no primers, adhesives or glues are needed for repairs, the fully torch patched Nuraply 3PT is as good as new.

Consider the Limits

As with all waterproofing, there is no silver bullet. Some additional things to consider are ground contamination — the presence of hydrocarbon contaminants, for example. Is a gas proof membrane required due to the presence of geothermal gases?

The team at Nuralite would love to assist with sub-grade tanking solutions. Remember, there is only one chance to get it right first time.