A Must-Read Guide to Successful Bad-Weather Screeding
When it comes to installing screed in bad weather, failing to prepare means preparing for failure. Though screed can be installed safely in wet or cold weather, adequate precautions should be taken to prevent early screed failure.
Winter is already here, and we can only hope that bitterly cold and snowy weather will not settle in too soon. Regarding flooring projects, the good news is that screed can be laid in almost any weather, as long as the outside temperature remains above 3°C.
Sure, there are some added challenges when installing screed in bad weather. But when extra care is taken, screed laid in winter performs just as well as screed installed in summer. Extra care basically means transporting and storing materials correctly, making sure the building is watertight, allowing the screed to dry completely and testing it. Now, let us discuss all these points in more detail.
Transportation and Storage
Since water can affect the properties of cement, aggregates, admixtures and additives, protecting materials from rain and moisture is extremely important to deliver a high-quality screed.
When carrying out screeding projects in wet weather, consider the following points:
- the sand should be loaded on to lorries at least 12 hours prior to the scheduled delivery time so that the water can drain out;
- during transportation, the sand should be covered securely with waterproof sheets, tarpaulin or canvas;
- cement should be transported in bags and protected from water; if cement comes in contact with water before the mixing process begins, its quality will be adversely affected, which will make it unusable;
- all materials should be stored in dry locations and protected from moisture and rain water; since cement bags are not completely waterproof, it’s best to store all the bags on pallets and cover them with waterproof sheets, tarpaulin or canvas.
Though certain admixtures can be used to reduce the water content in screed and accelerate its drying time, the screed mix will be too fluid if the sand is too wet. Since this will affect certain characteristics of screeds, such as flatness, levelness, strength and durability, alterations to cement-sand-water ratios should be made according to the moisture content of the sand. The snow-ball test can be used to assess the workability and consistency of the screed mix.
When laying screeds, building watertightness is extremely important to prevent screed deterioration. Though water infiltration or leaks may not cause any visible damage right away, they can negatively impact screeds in the long run. For example, water infiltrating through the floor may prevent the screed from bonding to the substrate, while water leaking from the ceiling can leave unsightly marks on the surface and affect the soundness of the screed.
The best way to protect freshly laid screed in wet or cold weather is to cover the surface with polyethylene sheets. The plastic sheeting should not be laid in direct contact with the screed, or localised damage may occur in areas where it touches the screed.
Curing and Drying Times
Since screed bleeding* and settlement takes longer in bad weather, screeds will need more time to cure and dry. Regardless of the formulations used, curing and drying time frames should be extended to allow screeds to dry completely and develop optimal strength. To speed up the setting process, cement, aggregates and admixtures should be acclimatised before mixing. Under no circumstances should screeds be laid when the air temperature falls below 3°C and the floor temperature below 5°C; an air temperature of 20ºC and a relative humidity level not greater than 50% are the ideal curing and drying conditions for screeds.
Since curing and drying times must be extended for screeds laid in cold or wet weather, testing screeds is critically important to ensure they have dried completely and developed the characteristics required. The calcium carbide test, BRE drop hammer test, laser level surveying and surface regularity tool are typically used to determine whether screeds meet or not project specifications.
At BuilderScreed, we specialise in both supplying and installing the right floor screed for a variety of flooring projects. An unparalleled level of knowledge, experience and craftsmanship complemented with exceptional attention to detail has turned BuilderScreed into a one-stop shop for any screeding needs. To find out more about our screeding solutions or to require a free, no-obligation quote, give us a call at 0845-500-4055.
*bleeding occurs in freshly laid screeds, as a result of excess water in the mix being pushed upwards to the surface during screed settlement.