Let it Work

Design so that there are a few layers so that even if one fails, the building is still waterproof

The second principle, let it work, focuses on buildability. Good designs often involve finding the simplest solution to complex problems, in order to avoid overcomplicating a situation. Overcomplicated designs can be challenging to build and are more likely to lead to error. 

Let it work is about creating designs that forgive the variance that occurs within the construction process. Implementing 'safety nets' in a design can allow a building to more easily mitigate the consequences of error. 

Safety nets help to account for the imperfect nature of on site construction conditions and the movement of buildings over time. Multilayered drainage systems are often implement considering let it work principles, acknowledging that if one layer is constructed incorrectly that it will not lead to an overall failure in the overall system. 

How To Design a Bathroom For Waterproofing

A majority of the problems when working with waterproofing in bathrooms lies in the floors. The main three elements to include when constructing a bathroom floor are a 50mm set down in the structural slab to the whole bathroom area, a 1:80 decline in the showers structural substrate, and a 1:100 decline in the bathrooms structural substrate. 

It is important to assess the bathrooms slab deflection plan in order to locate regions of sagging or hogging. Then assess the floor slab thickness and the required substrate sloping of 1:80 and 1:100. In accounting for all of this information it will be easy to calculate an accurate FFL and reduce the room for construction error. This revision of the flooring structure utilises the let it work principle to ensure success.

Sloped flooring provides a way for water to be directed toward the drainage zone through the let it flow principle. Use of slopped flooring provides a number of benefits. Any water that gets through the tiling layer will be able to make its way to the drain and high risk areas like wall junctions will be safe from danger. Additionally, the slab itself is able to provide a continuous barrier to water exit at the room's perimeter. 

How To Design a Balcony For Waterproofing

When designing areas that are open to the weather is essential to place rainwater elements, namely rainwater outlets and downpipes, in critical locations. When placing these elements consideration must be given to the slab itself. Areas of projected deflection should be located as they will become key water channels over time. Outlets should be placed where sagging is at its lowest. 

The ground slab should be constructed with a 1:80 fall to the rainwater outlet. Additionally, a 70mm set down will help in protecting the facade and stopping water from leaking at the wall junction. Calculation of micro-strain and curing procedures must be considered in construction of the slab and shrinkage steel should be included. This will help to reduce the likelihood of cracking and maintain the flow path of water towards the outlet. 

In accordance with the let it move principle joints in the concrete slab must be placed away from elements that can get wet. Pour joints and cold joints must not be used in balconies and topping layers and separate pours should be avoided. If used separate slabs with undergo differential movement and lead to leaks. 

How To Design a Podium For Waterproofing

Often there are large weather exposed slabs that cannot be built as a single slab. As such steps must be taken to minimize the impact of differential movement. With these slabs rainwater outlets must still be placed at the expected low points in the slab, with a 1:80 fall from the slab joint. This will act to draw water away from the joint. A 50mm rise must be cast at the location of the joint for further protection.

A waterproof membrane should cover the slabs, running continuously across the joint. An upward loop of the membrane should be placed centered on the joint as an extra safety net. A slopped sheet metal cap should provide the final layer of protection and should be fixed only to one side of the joint to allow for movement. This detail allows stress to be dispersed across all layers of the structure to create a level of redundancy. 

How To Design a Carpark For Waterproofing

Underground car parks pose an extra problem as they must deal with ground water coming in through the floor and walls. Within the wall structure a cavity must be present as it is inevitable that some water will be able to seep through the outer wall layer. The use of a cavity is important to stop the water from jumping to the internal layer by allowing space, free from capillary forces, for gravity to direct the water downward. At the bottom of the cavity should lie a spoon drain to collect the water from the bottom of the cavity. 

The floor of the carpark needs to be able to resist the rise of water up from the water table. Drains should be installed at key points such as joints and terminations. Surrounding the drains, a dense layer of aggregate should be employed in order to relieve any hydrostatic pressure and force the water towards the drains. If any additional upward momentum remains upside down drains can be used to discard the remaining water.