Charring performance of timber structures protected by traditional lime-based plasters

Abstract

There are limited performance data available on the fire resistance of lime-based plasters as a fire protection system for timber structures; no design values are given in the current fire part of Eurocode 5. This complicates the design and assessment of such (historic) building structures, as the contribution of lime plasters in case of fire is not clear. This paper aims to provide relevant data and assessment tools for the fire safety design and evaluation of the protection ability of lime-based plasters in combination with timber structures under standard fire exposure conditions. An overview of experimental studies in small and model-scale to determine the protection effect of various lime plaster systems is presented. The investigation is carried out in view of the design concept given in the European fire design standard with respect to the start time of charring of timber and the charring rate of timber behind the plaster system. Results present new knowledge and fire-related performance data of selected lime-based plasters regarding their protection ability under different heat exposure conditions and scales. References are made to the commonly used gypsum plasterboards and previous studies by the authors for an extended evaluation of test results. Obtained results demonstrate that thicker plaster coats are able to provide similar initial protection compared to the gypsum plasterboards for the start time of charring and the charring rate of protected timber until its fall-off.