How To: Prepare a Concrete Base For Your Garage

How to prepare a concrete garage base.How to prepare a concrete garage base

There is a saying in the garage industry ‘a concrete garage is only as good as the base it sits on’. It’s an old adage but it’s certainly true. Preparing a concrete garage base correctly is vital to the stability of any sectional concrete building. It may not be the most glamorous side of concrete garages but it is still important. So this week we will be looking at the do’s and dont’s of laying the perfect concrete base.

It’s all about the weight!

Concrete garages are heavy beasts. In fact the average single pent garage weighs in excess of two tonnes. If it’s an apex garage it will probably weigh over three, and that’s before you start with double garages or extra high buildings! For that reason alone we need to have a strong stable base to build our garages on. And for this reason we cannot build on tarmac, block paving or slabs. It has to be concrete.

So what constitutes a good garage base?

Lets look at the factors that will make up a good concrete base for garage:

  • The base itself should be 4″ thick in the main and 8″ thick around the outer edges
  • Underneath the concrete there should be a minimum 4″ of compacted hardcore
  • The edges of the base should be troweled off or chamferred to allow any water to drain off
  • Overall the base should be 3″ bigger than the building on all sides
  • Without wanting to state the obvious it should also be flat, square and level throughout

The picture below shows a cross section of how a good concrete garage base should be constructed (click on image to expand).

Other things to consider.

It’s amazing how seemingly little things have the potential to cause all manor of problems for the humble concrete garage. For example, if the base is too big and far exceeds the size of the building there is the potential for water to collect on the base. If enough water collects on the base it may try and squeeze itself into the building! This is why we recommend garage bases are 3″ bigger that the building on all sides. Chamferring the edge of the base also helps any water drain away from the building, not towards it!

It’s not just the base itself that is important but also the preparation. Laying a damp proof membrane underneath the concrete will prevent damp from rising up through the base causing problems with the building. It is also good practice, especially on larger bases to add reinforcing mesh to give the base extra strength and help prevent any cracking in the future.

The position of the building is also of importance. If the land slopes down towards the garage then a gulley will need to be added to take any water away rather than it flowing into the building. Likewise if there is a wall or bank around the building appropriate drainage will also have to be added.

In some situations where the concrete garage base is quite high in comparison to the surrounding ground level it might be necessary to add a ramp to the front of the base to allow easy access to the building. In this instance it is important to ensure the end of the ramp is not higher than the base itself. This will cause water to run back towards the garage where it could seep under the door.

Laying a good base for a concrete garage is mainly common sense, but following these simple rules will help to ensure the perfect concrete garage base. Our sales team are available here to answer any questions about concrete bases. We also have Lidget Compton Building Specialists all over the UK who can provide a concrete base laying service.