How to Lay a Concrete Slab: A careful approach is required for concrete Slab Laying. Your slab needs to be well-leveled and stable, so thorough preparation is crucial. You are required to get all the essential materials and tools for your slab before you begin the processes including:




Slab Laying


  • A mallet
  • A ball of string
  • Earth rammer
  • Wheelbarrow
  • Damp-proof membrane
  • Leveling tools which a rake and compactor included
  • Drill, timber, screws and nails
  • Tarpaulin and steel mesh
  • Four wooden pegs broom

You will require some items for your safety too, including;

  • Eye safety against dust, concrete dust and cement
  • Rubber boots
  • For your hands, rubber gloves

Long trousers and sleeves for your skin.
You are required to start the procedure of concrete slab laying with these tools and materials by following the guide:

Measure and Mark

You need to mark the slab area and measure the lengths between two opposite corners. Make sure all the angles are equal, and be careful about that. An ideal concrete slab is not too big or too small; it is medium-sized. Most certainly maintain your slab’s base the same size as that of the footprint of your building.

Dig Out the Marked Area

If you want a small slab, ferret out the decided area up to 175mm, and for a larger one, do the process of digging up to 225mm. Remove the pegs and string lines. Always make sure that there is a consistent length of your slab.

Lay-Out MOT Stone

You are required to layout MOT stone using a shovel. This is the stone that is utilized to observe industry or transport department regulations. You need to lay the crushed MOT stone in the dugout area. It plays an essential role in forming a long-lasting, sturdy and rigid base where you have to apply the layer of concrete.

Therefore it is necessary to ensure if you are working on a shed slab that the base is 4 inches deep. Let the base be extra deep of about 6 inches, if you are going to base a cabin or summerhouse.

Fit in Timber Rails

Measure it, cut carefully and smoothly fit timber rails on the base. You should be keen on the framework while doing this. Remember that the framework is catered for two purposes which include;

  • Levelling up the concrete
  • Generating a steady edge for your slab of concrete.

When fitting in timber rails, therefore, ensure the provision of enough space for concrete filling, and you do it carefully. The concrete will come out well if the framework is levelled up well.

Spread MOT Stone or Gravel

It is time to spread out MOT stone or gravel once you have filled up the rails. Utilize a manual or powered rammer to ensure you fill the stone in it firmly. This will assist in stopping any uneven or cracks in the concrete slab late on. You can also utilize powered Wacker plates, specifically petrol-driven choice, to spread the gravel.

It utilizes exceptional vibrations and is more powerful to strengthen the concrete slab’s base. You can always hire one if you cannot purchase since many companies are there to offer petrol-driven Wackerplates for hire.

Cover the Layer of Stone

You need to cover the gravel layer by using sand. You must utilize a generous amount and use a damp proof polythene membrane to cover the area. This is very much important as it assists to stop moisture from arising or escaping through the mix of concrete into your building’s floor bearers. Remember, sand will always fill gaps that can possibly cause your slab to sink. It also supplies extra safety so that the stone utilized will not harm the membrane.

Mix Concrete

You need to know the right concrete mix ratio and follow that as you can now mix the concrete for the concrete slab. You can utilize a cement mixer if you want to make a bigger slab, as a cement mixer offers an even mixture in the end. You also might have accurate quantities for concrete slab laying as it will also enable you to have the correct quantities. If the ratio is not right, the first mixture batch will be hard; this is the point to note.

Your slab of concrete will not come out as wished as a result. Therefore, you need to have a ratio of 1 bag of cement: 1 bag MOT gravel: 4 bags sand and water. For 1 kilogram of cement, you need to use half a litre of water. It is also essential that you mix a plasticizer with your mixture. The amount of water is significantly reduced by the mortar plasticizer that will be utilized for a smoother mixture of concrete.

It also makes sure that the mixture, as you work, does not shrink. When the mixture is dry, it becomes more resistant and stays flexible to the harmful effects of frost. You can use 150ml of plasticizer in 25 kgs of water mixed cement for the best consequences. Add this to your sand and cement. You should be careful and do not add more water if you realize that the sand is wet while making a concrete mixture.

It assists in making sure that the blend is just smooth enough to give the right stability but not sloppy for your slab. The proper and quality concrete slab should be stiff and hard enough to maintain a pile on shovel scoop.

Concrete Slab Laying

You can now begin concret slab laying with a good mixture. You are required to:

  • Spread the concrete evenly around timber rails. Utilizing a straight timber, start levelling following a sawing motion.
  • Once you have smoothed it over carefully, brush across the surface. Utilizing a stiff broom, lightly brush through or across the base. It assists in generating a textured and non-slip surface.
  • You can now use a polythene membrane or tarpaulin to cover the base and let it stay for at least 24 hours during the cold season. You can just use a sack to cove it, keeping it damp if the temperature is high. It stops possible cracks in the concrete slab and keeps it in good condition.
  • Let it preserve for about three days. This perseverance period permits the concrete slab to stiffen and achieve its solid strength. Once the concrete slab is wholly preserved, remove the timber rails.
  • The space remaining around the edges of your concrete fill that space. Remember, when removing timber rails while building concrete slabs, spaces are left unfilled. Therefore, to drain and fill in excess moisture from your base, utilize pea gravel.

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