Using Handheld Moisture Meters on Limestone: Factors Affecting Performance and Guidelines for Best Practice: Fid-Bau Portal

Using Handheld Moisture Meters on Limestone: Factors Affecting Performance and Guidelines for Best Practice

Eklund, Julie A. / Zhang, Hong / Viles, Heather A. / Curteis, Tobit

Hand-held moisture meters are frequently used by conservators and conservation architects for the non-destructive investigation of dampness problems in stone and mixed building structures, despite such meters being primarily developed and calibrated for wood. Following extensive use of hand-held moisture meters on historic stone monuments under field conditions, we tested one resistance and two capacitance meters on Portland limestone in a laboratory setting. We found that each meter provided different readings on three types of limestone at the same moisture content. Readings from different meters were neither comparable nor predictable, as their relationship varied by substrate. Meter readings are therefore only of value when used relative to each other for any given surface/meter pairing, either by surveying several points over the same surface or monitoring the same points. Additionally, several factors were investigated for their contribution to variance in meter readings, and guidelines for best practice are presented. Despite the complexities observed when using moisture meters on stone, each moisture meter was found to produce reliable readings that could be related to absolute moisture contents for individual stone types. Thus, when used with care, hand-held moisture meters can provide good indications of the moisture contents of limestone.