Whether you are looking for guidance on your next project or simply a refresher on the best liquid or traditional screed applications, our simple guide can help you understand this surface. If you are entirely new to using screed as a material, visit our introduction to screed blog post to learn more.
What are the Different Types of Floor Screeds?
The variety of screed you use will depend on the type of concrete base, your expectations for the surface, and the standard of your foundations
There are three standard categories of screed available on the market: bonded, unbonded and floating all of which can be applied through both liquid and traditional screed methods.
Bonded: This is directly connected to the concrete subfloor (substrate) with an adhesive. The surface of the concrete must be roughened, and a bonding agent thoroughly applied for application to be successful. This thinner application typically lies between 25-40mm
Unbonded: Laid on a PVC/damp-proof membrane, separating it from the concrete substrate makes this surface an excellent choice in buildings where dampness presents a severe problem. This type of screed is ideal for thicknesses exceeding 50mm.
Floating screed: These unbonded surfaces are often used to reinforce an acoustic or thermal layer. In order to remain effective and long-lasting floating screed requires a minimum thickness of 65mm.
Liquid screed, also known as anhydrite screed, uses a binding agent called calcium sulphate instead of cement. Once water has been added, a reaction occurs, which creates gypsum until the calcium substrate has been depleted. This makes for a highly durable, self-levelling sub-floor, compatible with all floor types. This form of screed offers a low environmental impact and a range of benefits over traditional screeds. They are pumped, free ﬂowing and can be installed in bays of up to 1000m2 before any expansion joints to reduce movement are required. They hold twice the thermal conductivity of traditional screeds, making them ideal for underﬂoor heating applications.
Traditional Floor Screed
Traditional sand cement screed is regularly projects of all sizes, from domestic to large scale industry and commercial applications. Mesh and/or fibres can be added to increase strength and durability and reduce cracks caused by shrinkage.
What are the Advantages and Disadvantages to Liquid Screed?
Liquid screed lends itself to many applications, but its effectiveness depends on location and usage.
Advantages of liquid screed include:
Low labour costs: As liquid screed is poured from a hose, it can be over ten times quicker than laying a traditional screed surface, cutting down on overall labour costs.
Cost reduction: Costs are further reduced due to thin application depths, down to 35mm. Underfloor heating included, depths could be as low as 45mm in total, still remarkably thin by conventional standards.
Self-levelling: Pumped liquid screeds are effectively self-levelling and self-curing, translating into a sleek finish. This is particularly useful for remedying precast concrete beams and block floors with a camber that may cause problems when laying the final floor surface.
Suitable for underfloor heating: The liquid consistency envelopes the pipes eliminating voids and enhancing heat transfer between the pipes and the screed.
Disadvantages of liquid screed include:
Involved prep work: An expert must correctly prepare the initial pouring surface and final product before embarking on the next stage. This can cost you both in labour and in tools as screed cannot be poured without the floor first being sanded, tanked and any insulation covered by polythene. The final product must also be sanded as curing liquid anhydrite screed produces laitance, which could potentially impair the laying of the floor above it.
What are the Advantages and Disadvantages to Traditional Dry Screed?
Advantages of traditional screed include:
Durability: These hardwearing, durable surfaces work perfectly in heavy load applications and can last many years.
Energy efficiency: These floors commonly possess a high thermal mass. This can help improve the building’s thermal retention, improve energy efficiency, and reduce waste energy and cost.
Damp resistance: Once cured, traditional screed is non-absorbent. Lending itself to applications such as basements or industrial buildings.
Low maintenance: Traditional dry screed is easily maintained with a stiff brush and warm soapy water. It can also be polished to give it a more aesthetic appearance if left bare.
Disadvantages of this method include:
There is no adequate patching method available: If a large crack, fissure, or pothole appeared on this surface, it is almost impossible to patch in a way that doesn’t act as a weak point later down the line. This can be very costly as if something severe happens to this screed, as it will have to be entirely replaced.
No flexibility: Unlike liquid screed, once set, traditional screed has minimal to no flexibility, making it prone to cracking when general subsidence or land movement occurs.
What Type of Screeding Works Best for Different Projects?
Screed is as unique as your project and can be adapted to your individual needs, for example, adding resilience by incorporating mesh. The screed you choose can dramatically impact the outcome of your project, so before booking, we recommend you talk to our team, who can help guide you through the decision-making process.
Start a Conversation with Axtell on Your Next Project
Axtell are leading providers of liquid screed services across our area. With over 20 years of knowledge and experience, we are proud to provide the highest quality of products and services at the best prices. We are proud stockists of LKAB Gypsol classic and Gypsol Rapide Screed, both renowned for their respective environmental credentials in their sector.