01248 353 595 Yes, you can put a sand-cement screed directly onto hardened concrete, as long as the slab is sound, clean, and properly prepared. In most cases, that means roughening the surface, removing laitance, dust and contaminants, and using a suitable bonding slurry or primer so the screed really grabs the concrete.
You’ll also need to check moisture levels and make sure any damp-proofing is in place so you don’t trap moisture under the screed or your final floor finish. Key Considerations when screeding onto concrete:
Surface Preparation: The surface of the hardened concrete must be clean, free from dust, oil, grease and any loose material. Proper preparation helps ensure good adhesion between the screed and the concrete.
Damp Proofing: If there is a risk of moisture coming from the concrete (such as in cases of rising damp), it may be necessary to apply a damp-proof membrane (DPM) before laying the screed.
Bonding Agents: In some cases, using a bonding agent can enhance the bond between the screed and the concrete substrate, especially if the concrete surface is very smooth or polished.
Expansion Joints: Consideration should be given to any existing expansion joints in the concrete. These should be replicated in the screed to prevent cracking.
Curing: Proper curing of the sand cement screed is essential to prevent cracking and ensure strength. Follow recommended curing practices to achieve optimal results.