How to prepare for a concrete garage  base

1. Preparing the garage base

To prevent your garage floor concrete slab from cracking, it’s important to have a solid and level base. Additionally, if the ground level is to be built up, then proper compaction must be ensured to avoid uneven settlement.

Make sure you remove all plant matter, rocks and debris and compact the area before adding the hardcore sub base and compacting again. You should have a solid compacted hardcore base on the soil, on which the reinforcement can be placed. The depths of hardcore will vary depending on ground conditions so we would recommend checking with your architect or builder.

Then lay a Damp Proof Membrane (DPM) – ensuring the edges are turned up to form a tray and any joints are overlapped and taped.

Create a timber frame to contain the concrete. Use a spirit level to check the frame sits level on top of the hardcore and make any necessary adjustments. Place wooden pegs inside the frame at regular intervals to hold it in place. Sit pegs below the top level of the frame to make it easy to level off the concrete.

Overall the base should be 175mm bigger than the building on all sides.

2. Measuring the thickness of the garage floor slab

The thickness of the garage floor slab depends on factors such as:

  • Types of loads placed on the slab
  • Climatic condition
  • Mix of the concrete
  • Span of the concrete

Standard thickness of the garage floor slabs used worldwide is 150mm. Depending upon the load placed on the slab, the thickness should be adjusted. Typical examples are:

  1. Light Loads – For one to two light cars, the concrete should be at least 100mm thick
  2. Medium Loads – If the garage is used for average-sized vehicles and/or medium to heavy trucks, the concrete needs to be 150mm thick
  3. Heavy Loads – If your garage floor is going to see constant traffic from heavy vehicles, it is recommended the concrete is 150mm to 200mm thick. The floor must also be treated and sealed properly to avoid heavy loads, like large trucks, cracking the concrete

3. Reinforcement

The reinforcement steel should be used just to hold the slab in position and avoid cracks. The slab will be supported by the ground underneath.

4. Placing of Concrete

Before placing the concrete make sure you have all the necessary tools and labour available to help. Having enough labour is often over looked and you can run the risk of the concrete going off before you have had chance to level it off and finish with a trowel.

Typical basic tools required:

  • Shovel
  • Rake
  • Timber tamp (i.e. length of 4×2” timber)
  • Hand trowels
  • Spirit level or laser level

When placing the concrete work in 1-2m strips across the width of the slab, levelling with a tamp and finishing with trowels as you go. A shovel and rake will be needed to help move the concrete around.  A vibrating poker can be used to help level and compact the concrete.

The edges of the base should be chamfered to allow any water to drain off.

For bases that are difficult to access, such as at the bottom of your garden and for large concrete pours where the use of wheel barrows will be very time consuming, we would recommend using one of our concrete pumps, which will pump the concrete directly from the concrete lorry to the pour area saving you on time, labour and hard work! Call us for a quote

5. Curing of Garage Floor Slab

Use slab curing methods, such as a water cure. Concrete is flooded; ponded, or a mist sprayer is used, to ensure proper curing of the garage floor slab and to help prevent shrinkage cracks

It is important to allow sufficient curing time before applying any finishes to your garage floor as moisture on the slab may cause the finishes to lift or debond.

6. Finishing for Garage Floor

You can finish the garage floor using:

  • Garage Floor Epoxy
  • Garage Floor Paint
  • Garage Floor Mats
  • Garage Floor Tiles
  • Polished Concrete Flooring.

How much concrete is needed for a base?

Estimating concrete quantities can be a difficult, frustrating and often expensive task. You can use our concrete calculator to calculate how much you think you will need and we will arrive on-site and mix the exact requirements for the job.

Help and Advice

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