A blog written by ForceDry

Understand your screed drying times

Most screed brands on the market give you their products natural drying times so you can plan your programme time. Many modern screeds boast being able to take foot traffic very quickly after just a few days or even hours. This is often confused as being the date the screed is completely dry and ready for a floor finish to be laid which it is not.

The majority of quick-dry, anhydrite screeds advise they can dry as quickly as 1mm per day for the first 40mm then 0.5mm per day thereafter. Poured to an industry average depth of 50mm would mean the total natural drying time would take just 60 days.

Compared to traditional sand and cement this would allow you to move forward with your project much more quickly.

Read the small print

Natural drying times are calculated using many factors, the two most common are the depth the screed is poured and the environment the screed needs in order to dry.

Many modern, quick dry anhydrite calcium sulphate screeds are designed to be poured at very shallow depths. Less depth means less product and much quicker drying times which has revolutionised programme times.

Regardless of the brand or type of screed, what most have in common is the second factor, the environment the screed needs to experience in order to dry naturally. It may vary slightly but most need a consistent 20°c temperature and 65% relative humidity or RH as it’s known, 24 hours a day for the entire 60 days.

Be realistic

The UK does not experience this kind of temperature and RH often. During the hottest year on record in 2018 no consecutive 60 days delivered 20°c and 65% RH so it’s not realistic to only allow the minimum drying times. During Autumn, Winter and Spring these conditions are far from realistic so you should consider ways you can help create this environment and help your screed dry as quickly and safely as possible.

There are some basic elements you can introduce which can create and maintain the perfect environment not just for you screed but for all the other wet trades too!

1 – Heat

For projects with traditional radiators you should consider turning on your heating system to provide a consistent background heat and keep the building and environment warm.

If your project has underfloor heating you have the opportunity to run a full force dry programme and dry your screed even more quickly. This is a very specific and controlled programme so take advise from your manufacturer or contact ForceDry to discuss.

If your project does not have a working boiler or heating system, consider hiring specialist temporary boilers so your project can keep pushing forward.

2 – Dehumidification

When water evaporates from the screed the air becomes saturated so it’s unable to carry any more. This saturation impedes the drying process, slows progress and impacts drying times.

Dehumidifiers are essential to extract and manage the moisture in the air above the screed. The dry air then recirculates over the screed and encourages it to give up even more moisture and helps it to dry quicker.

The exact number of dehumidifiers you need will depend on its capacity and the cubic volume or M³ of the dwelling. The bigger the capacity of the dehumidifier the fewer you will need.

Dehumidifiers should be placed centrally within a room so they can see and service the biggest volume of air. Never place them facing a wall, behind an open door or tucked in a corner. If they can’t see the air, the can’t manage it. You should also consider moving them around regularly, so all areas of the dwelling benefit.

3 – Air Flow

It’s important to ensure dehumidification is being managed evenly throughout the dwelling. This is so you can avoid pockets of still, saturated air from building up and impeding the drying process in some areas. Screed should dry consistently throughout the property.

To do this you need excellent air flow to move the heavy, moist air around the dwelling towards the dehumidifiers so they can work their magic!

Consider the layout of your dwelling, if there are lots of smaller rooms, or areas far from where your dehumidifier can reach you should place fans there. Keep internal doors open so the air flows nicely around the property.

Fans should be positioned facing into the main body of a room or hallway so the air flows as far and as wide as possible. You should move your dehumidifiers and fans regularly to make sure the whole property benefits evenly.