Lack of space is one of major challenges in residential construction. This is especially true in the Wellington region, with Cook Strait to the south, Makara Valley to the west and two mountain ranges due north of the city. But people still need places to live, which is why infill housing (where you build in an area that’s already developed) is a great way to meet this challenge.
Like everything, infill housing has its own set of challenges. Two of these are stormwater and tight spaces. We’ve recently started using a product called Aquacomb to resolve these issues on infill properties.
What is Aquacomb?
Aquacomb is compact, flexible water storage system. It’s a natural fit for us because of the way we use void formers in our slabs. Void formers are a response to one of the challenges of concrete: in most cases, a solid block of concrete will be heavier and more expensive, but no more supportive than a smaller amount of concrete spread over the same space. So we pour concrete over void formers to give slabs shape.
The void formers - generally polystyrene blocks - give the slab the shape we need, while reducing the amount of concrete we need to pour, without compromising structural integrity. But there’s no reason these void formers need to be polystrene. They can be anything that fills the space.
Aquacomb lets us get more value out of this space by using water tanks as void formers rather than polystyrene blocks.These water tanks sit under the house, completely out of sight, and attach to the house’s gutters and downspouts. When it rains, stormwater goes into these tanks. From here, it can either trickle slowly into the council stormwater system, or be reused for things like clothes washing and toilet flushing.
Aquacomb tanks can also be stored under a deck or patio - or even behind a retaining wall.
So that’s what Aquacomb is. But here’s the bigger question: why use it?
Council stormwater management has a ‘peak load’ problem. The communal gutters, pipes and drains are usually sitting idle - but when it rains, they need to handle large amounts of water at one time. Infill housing can increase the strain on these systems during storms, particularly if they are projects like townhouses or apartments that have replaced lower-density buildings with smaller footprints. Replacing absorbent grass with hard surfaces means less water absorbing into the ground, and more water running off into the stormwater system.
If these systems are already at or near capacity, local councils may be less-than-enthusiastic about consenting a project that may put more strain on them, as strain on stormwater systems quickly turns into flooding.
WIth this in mind, Aquacomb can be the difference between a project being consented or not. By storing water in the foundations, and either re-using it, or slowly trickling it into the council system after the storm’s over, Aquacomb can reduce the impact on the local stormwater infrastructure.
Slow release, at grade
In some cases, you may be able to use the council stormwater system, but will need to slowly release any stormwater into it. This helps to deal with the peak load problem mentioned above - a stormwater system that is at capacity will generally be only at capacity during heavy rains, and well below capacity after a couple of days.
This means you need to store it for a period of time, which means you need a tank. One approach to this problem is to direct stormwater into a buried tank. But on some sites, a buried water tank ends up below the council stormwater management system - which in turn means that the water can’t flow into the system without a pump.
Aquacomb can be laid at ground level, by putting it in the home’s slab. This gives you the ability to both store the water during a storm, and slowly release it into the council stormwater system.
If you can’t bury a water tank, you need to put it somewhere else, such as attached to the side of the house. This is particularly relevant on infill housing developments, where space is limited. The space used by a water tank is space that could be used by a deck, green space or a bbq.
Aquacomb gives you the ability to both store your water at grade, while also conserving space. The space saved can be put to work providing something more valuable to the home’s residents.
So if you’re working on a site where stormwater management may be an issue, have a think about using Aquacomb. It’s an affordable, flexible and scalable solution for infill developments.