In this blog ForceDry discuss digital hygrometer testing which is fast becoming the construction industry’s first choice for screed testing.

What is a digital hygrometer?

Digital hygrometers are also referred to as hood hygrometers. They are small box like, non-invasive devise which is temporarily fixed and sealed to a screed floor to measure the relative humidity or RH levels within the screed.

What does a digital hygrometer do?

A digital hygrometer is used to test a sub floor or screed to make sure it’s dry enough for the final floor finish to be laid. It uses a thermo hygrometer to test and collect the relative humidity and air temperature to record the floors moisture level as a percentage.

How dry the screed needs to be will depend on the final floor finish. An industry standard is 75% for many floor finishes, for more sensitive finishes such as wood it is often 65% or even lower. Each product type and brand have their own requirements, and it is important to understand this before testing so you understand what the target RH is.

How is digital hygrometer testing carried out?

For projects with underfloor heating installed, all heat must have been switched off 2 days in advance to allow the screed to cool completely. Dehumidifiers are used for 2 days before the test is applied to ensure the humidity in the air is dry before the digital hygrometer is installed.

A specialist tape is used to secure the box like device to the screed and keep it in place so the air trapped inside the box remains sealed from the outside.

Suitable locations are found to install the digital hygrometers where they are safe from being kicked, knocked, or damaged. They are sensitive tests so if they are interfered with this would compromise the accuracy of the test results.

Depending on the screed product and its thickness, the digital hygrometer must be left in place for a short time until the air has reached what is called a moisture equilibrium. After this time, the readings are collected and compared to the target RH levels required for the final floor finish and this determines if the screed is wet or dry.

Your RH levels not at their target?

See our guide on What to do if screed is too wet to lay the floor finish