Screed Calculator

Calculate material & drying time

Screed Calculator – Accurately Calculate Material and Drying Time

Planning a flooring project? Whether you're working on a new build, renovation, or commercial construction, calculating the right amount of screed material is essential for a successful result. Our free screed calculator helps you determine exactly how much material you need and how long the drying process will take, saving you time, money, and unnecessary stress on site.

What Is Screed and Why Does the Calculation Matter?

Screed is a thin layer of cementitious or anhydrite material applied to a subfloor to create a smooth, level surface ready for the final floor covering. It is used in homes, offices, warehouses, schools, and virtually every type of building. Getting the quantities right matters for several reasons:

  • Too little material and you'll have an insufficient layer that cracks or fails
  • Too much material means wasted money and excess weight on the structure
  • Incorrect drying time estimates can lead to premature floor covering installation, causing costly damage

Our calculator removes the guesswork and delivers accurate results in seconds.

How to Use the Screed Calculator

The tool is designed to be intuitive and accessible for both professionals and DIY enthusiasts. Simply enter the following values:

  • Area (m²): The total floor area to be screeded
  • Thickness (mm): The required screed depth, typically between 30 and 80 mm
  • Screed type: Choose from cement screed, anhydrite (calcium sulfate) screed, or dry screed
  • Room conditions: Temperature and humidity for drying time estimation

The calculator instantly provides the material volume in cubic metres, weight in kilograms or tonnes, and an estimated drying time based on your inputs.

Types of Screed Explained

Cement Screed (CT)

Cement screed is the most widely used type, valued for its strength, durability, and versatility. It works indoors and outdoors, and is compatible with underfloor heating systems. A general rule of thumb is that cement screed dries at a rate of approximately 1 day per millimetre of thickness, meaning a 50 mm layer takes around 50 days to fully cure under standard conditions.

Anhydrite Screed (CA)

Also known as calcium sulphate or flow screed, anhydrite screed is pumped onto the floor and self-levels, making it ideal for large areas and underfloor heating installations. It dries faster than cement screed – roughly 1 day per 1.5–2 mm – but must not be used in wet areas such as bathrooms or shower rooms.

Dry Screed

Dry screed panels, typically made from gypsum fibreboard or chipboard, are laid without any wet process. They are immediately walkable and ideal for rapid refurbishments or where structural loading is a concern. No drying time is required, but careful subfloor preparation is essential.

Understanding Drying Time

One of the most critical aspects of any screed project is allowing sufficient drying time before laying the final floor covering. Installing tiles, carpet, hardwood, or vinyl too soon can trap moisture, leading to bubbling, warping, mould growth, and adhesive failure.

Key factors influencing drying time include:

  • Screed type: Anhydrite dries faster than cement screed
  • Layer thickness: Thicker layers take significantly longer to dry
  • Room temperature: Ideal range is 15–22°C
  • Relative humidity: Lower humidity speeds up drying
  • Ventilation: Good airflow removes moisture-laden air

Our screed calculator incorporates these variables to provide a realistic drying time estimate tailored to your specific conditions.

Real-World Calculation Example

Imagine you're screeding a living room of 25 m² with cement screed at a thickness of 60 mm. Here's what the calculator would show:

  • Volume required: 25 × 0.06 = 1.5 m³
  • Material weight (at ~2,000 kg/m³): approximately 3,000 kg (3 tonnes)
  • Estimated drying time: approximately 60 days under normal indoor conditions

These figures give you a solid basis for ordering materials, scheduling trades, and planning the overall project timeline.

Pro Tips for a Successful Screed Installation

  • Always clean and prime the subfloor before pouring
  • Install edge insulation strips around the perimeter to allow for expansion
  • For underfloor heating, pressurise the system before screeding
  • Keep the screed covered and protected from draughts and direct sunlight during curing
  • Use a moisture meter to verify the screed is dry enough before laying floor coverings

Frequently Asked Questions

How much screed do I need per square metre?

It depends on the thickness. At 50 mm depth and a density of approximately 2,000 kg/m³, you'll need around 100 kg per square metre. Our calculator gives you a precise figure based on your actual inputs.

How long does screed take to dry before tiling?

Cement screed typically needs around 1 day per millimetre of thickness. A 50 mm layer would therefore take approximately 50 days. Always conduct a moisture test before tiling to confirm readiness.

Can I walk on screed after 24 hours?

Light foot traffic is usually possible after 24–48 hours, but the screed will not be fully cured or ready for floor coverings for several weeks. Avoid heavy loads during this period.

Is the screed calculator suitable for underfloor heating projects?

Yes. The calculator accounts for the additional thickness required over heating pipes and cables, and adjusts drying time estimates accordingly for heated screed systems.

What is the minimum screed thickness?

The minimum recommended thickness for a bonded screed is around 25 mm, while unbonded screeds should be at least 50 mm thick. Over underfloor heating, a minimum cover of 45 mm above the pipes is generally recommended.

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