When you think of building with screw pile foundations, they’re usually as an alternative to concrete. But what if you’re working with a reinforced concrete raft, in an area with very little space? Somewhere that abuts another building. Or where conditions – such as a high water table or sedimentary soil – dictate that deep excavation simply isn’t viable? Could helical piles provide the stability necessary to secure the structure?
Using Screw Piles with a Concrete Raft
Can you use screw piles with a concrete raft?
The simple answer here is, yes. Known as a piled raft foundation, this arrangement consists of a reinforced concrete raft supported by screw piles screwed into the soil. This option would be used to increase the load-bearing capacity of the structure in a range of conditions. Or where space limitations restrict the use of other foundation types.
Under what conditions would you use screw piles with a concrete raft
Piled raft foundations are usually selected for projects where the soil is highly compressible or sedimentary. And/or where the water table is high. Under these conditions, screw piles can help to reduce any potential settlement. This arrangement also allows for better buoyancy management.
Is there a limit to the size of the structure that can be built on piled rafts?
Piled rafts can be used on a range of project sizes. From small beach cabins to high-rise buildings. As long as you seek advice from structural engineers to ensure that you have the right size and type of helical pile for your project, you can build with confidence.
How do you use screw piles with a concrete raft?
For this type of structure, you would install the relevant helical piles in the ground at specified intervals. Working either by hand or using a groundworks vehicle.
(In this image the pile caps are incorporated into the steel work as part of a strip foundation, a similar method is used for incorporation into a raft)
What are the benefits of using screw piles with concrete rafts?
The main advantage of using screw piles with a concrete raft is that screw piles allow you to work in smaller spaces and adverse conditions while allowing you to increase the load-bearing capacity of certain soil types. Because screw piles are quick to install and can be laid in any weather, they provide a quick solution in less than straightforward conditions. They can also be cost-effective and are always low-impact.
Are there any disadvantages to using screw piles with a concrete raft?
Concrete raft creation requires a degree of expertise. It is not something that most people can simply do at home. And this can be a disadvantage because the process can be costly. Concrete rafts can also erode if not properly looked after. So in summary, you’ll need an engineer and an experienced groundworks team.
For most DIY projects, screw piles and concrete rafts will not provide a viable solution. Simply because of the expertise involved in creating the raft. But in certain circumstances, this combination can enable structures to be created in places that you may otherwise have dismissed. Making it a useful arrangement to be familiar with.
If you need helical piles for your next building project, get in touch with UK Helix.
Disclaimer –Information in this blog does not in any way constitute building advice or guidance for private or commercial building projects.