This test method involves drilling a hole into the concrete and apply a liner to the inside of the hole. A sensor is then placed into the hole which measures Relative Humidity (RH) and temperature.
The liner used must have a solid sidewall that is open at the top and bottom only. Slots, holes or any other penetrations in the sidewall of the liner are not permitted. Two or more deformable circumferential fins located around the exterior circumference near the bottom of the liner shall be provided to create a positive seal against the concrete. The liner shall be of sufficient length to extend from the bottom of the hole to the surface of the concrete.
Depth and Testing locations
On site the moisture points are numbered and marked on the concrete slab using spray paint / writing on tape and listed on the plans provided. Depth of concrete for each point is recorded on our worksheet matching the number written on the concrete floor. Depth is calculated based upon slab thickness – 40% if the slab is in the ground or 20% if the slab is suspended (drying top and bottom), which is written on our worksheet. A 20mm hole is drilled to the nominated depth and the hole and surrounding area is vacuumed. The hole liner is cut to the depth of the hole where outside fins of the liner is at the bottom, apply silicon to the liner and then insert this in the hole. Then place sensor probe into the liner where the top of the sensor is within 15.875mm of the bottom of the hole. Apply stopper at the top of the liner and update worksheet for each hole.
Allow a minimum of 24 hours to achieve moisture equilibrium of the slab within the hole before testing can proceed. All information is progressively recorded on our worksheets as the testing is performed. When taking Relative Humidity (RH) readings, testing signage is erected to protect equipment, remove cap, connect the sensor probe to the moisture meter and allow time for the meter readings to settle, record RH and temperature, wait 5 minutes and record the RH and temperature again. The RH reading must not drift by more than 1% relative humidity over this time period. If so, continue to re-test every 5 minutes until this standard is obtained. At completion, remove the sensor from the hole and place cap back into the hole. Photo of the results can be taken if requested by the client.
Complete clients report as per appropriate Standard. Concrete subfloor is considered sufficiently dry when measurements taken do not exceed 75% RH.
Photo of the results can be taken if requested by the client as well as pH testing if specified.
Taking readings for new slabs is normally done as late as possible in order to allow the slab to dry. Consequently, a lot of building activity is occurring when holes are drilled and testing conducted. Hence, protecting the hole, which has a sensor in the liner with a slightly protruding cap at the top, over the minimum 24 hours required is recommended so as to prevent any damage occurring.
Filling in drilled hole
Remove hole liner and if this is not possible, cut as much off the top as possible (e.g. use a Stanley knife). Fill the hole with a cementitious / levelling patching compound to produce a surface finish in accordance with Practice F710 (paragraph 4.5 under General Guidelines). Use a patching compound rated by its manufacturer as suitable for the depth of the patch required.