What Is Concrete Screeding?

What Is Concrete Screeding?

What Is Concrete Screeding?

Screeding is the process of leveling and smoothing out freshly poured concrete to prepare it for finishing. It involves using a flat tool to remove excess concrete and create a level surface.

After screeding, the concrete is typically floated with a hand or bull float to further smooth and compact it.

Floating brings fine aggregate and cement to the surface of the slab and helps to create a smooth, even finish.

However, screeding is just one step in the process of finishing concrete, and it is not intended to produce a completely smooth, finished surface on its own.

What Is The Purpose Of Screeding Concrete?

The purpose of a levelling screed, made from a mixture of cement and sharp sand, is to create a smooth and level surface for laying a final floor finish such as carpet, linoleum, laminate, vinyl, wood blocks, or tiles.

The screed should not vary in height by more than 5mm over a distance of 3 meters. It is not meant to be a wearing surface and should always be covered with a final floor finish.

When installing underfloor heating, a screed is the preferred medium. To prevent movement issues, it is recommended that screeds do not cover an area larger than 40m² or a distance longer than 8m in any one direction.

Expansion joints or anti-crack mesh can be used to divide larger screed areas or fibers can be added to the screed mixture.

What Tool Is Used For Screeding?

Using a 2×4 piece of lumber to screed concrete may not produce satisfactory results because the board may be slightly warped or have a beveled edge or knots, which can require multiple passes to achieve a level surface.

In addition, a 2×4 cannot accurately determine if a surface is truly level. On the other hand, a screeding level is a tool specifically designed for this task and is completely flat on the edge that touches the concrete.

It also has a level vial that allows the user to see if the surface is level or if additional passes are needed.

A good screeding level is made of durable aluminum alloy, is capped at both ends to prevent concrete from entering, and has smooth, crisp edges to facilitate the screeding process and produce a smooth surface.

Overall, a screeding level is a more effective and efficient tool than a 2×4 for screeding concrete.

How Is Screeding Done?

To screed a floor, you will need to follow these steps:

  • Clean the concrete floor to remove any dirt or grease.
  • If you are using unbonded screed, lay down plastic sheets or another type of membrane to protect the concrete floor. Overlap the sheets by 20-30cm and tape them together to prevent leakage. Use insulation or edging foam around the walls to prevent damage when the screed shrinks during drying.
  • If necessary, reinforce the screed with fibres or screed reinforcement mesh.
  • If you are using bonded screed, roughen the surface of the concrete to increase adhesive potential. Remove any dust or debris and apply a bonding agent to the concrete.
  • Divide the floor into sections using timber battens.
  • Spread out the screed with a trowel, then use a screed board or other straight-edged tool to compact and flatten it. Repeat this process until the whole floor is covered.
  • Allow the screed to dry for at least 24 hours before walking on it or applying any finishes.

Note: The thickness of the screed will depend on the type you are using. Unbonded screed should be around 50mm thick, while bonded screed should be 35-40mm thick.

How Long Does Floor Screed Take To Dry?

A sand and cement screed floor can be walked on after approximately 48 hours, but it must undergo a curing process before it is ready to have anything else installed or laid on it.

During the curing process, the screed is allowed to gradually set over a period of several days, during which it is covered with a thick polythene sheet to prevent it from drying out too quickly and becoming too rigid or cracking.

The curing process typically takes up to 7 days, depending on the temperature and humidity in the room where the screed is being laid.

After the screed has cured, the polythene sheet is removed and the remaining moisture is allowed to dry out over the course of 24-48 hours.

It’s worth noting that the terms “drying” and “curing” are often used interchangeably in the building trade, but they actually refer to different stages in the process of preparing a sand and cement screed floor.

What Is The Difference Between Plastering And Screeding?

Plastering is a process used to protect walls and ceilings from damage and improve their appearance.

It involves applying a thin layer of cement mortar to the surface to smooth and flatten it, and is often done before painting to prepare the surface.

Professional plasterers are recommended for this task to ensure the best quality result. Screeding is a technique used to level and smooth the top layer of a material, such as concrete, so it is even with the surrounding forms or guides.

It is commonly used in landscaping and gardening projects, such as building a patio, and involves using a tool to evenly distribute the material and make it smooth.

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