INGENIEUR
Figure 6 : Mortise and tenon joint at a longhouse ( Source : Hashim et al ., 2020 ).
lichen occurs by way of organic acid as well as hyphal penetration and pressure exerted by thalli ( Salvadori & Municchia , 2016 ).
Fungi and lichens can be removed using physical tools such as vacuum cleaners , scalpels , and spatulas . It should be noted however that without inhibiting fungi and lichen growth , the same problem can easily reoccur after manual removal . Furthermore , concerning lichens , a strong peeling effect can occur from manual removal methods , hence it is not encouraged ( Municchia et al ., 2018 ). The combined use of mechanical tools and laser tools provides satisfactory results , though this method cannot remove the thalli that are buried deep inside the construction material ( Rivas et al ., 2018 ). The use of gamma radiation can induce a chemical reaction in cellulose molecules , which leads to the breakdown of molecule linkage ( Adamo et al ., 2001 ) and a higher frequency can be used to combat wooddestroying insects . However , the effects of using gamma radiation are not long-lasting .
Treatment for biodeterioration can also be done using biocides , which can be considered to be one of the most effective methods to control microorganisms for heritage buildings as the biocides are highly toxic to living micro-organisms . Biocides generally work by suspending the metabolic action of microbes , thus altering the proper functioning of microbial cells , causing cell death . Examples of commonly used oxidising biocides are hydrogen peroxide , bromine , chlorine , and ozone .
Another possible source of damage to heritage buildings in Malaysia is earthquake . Long considered a non-factor in Malaysia , the 5.9 Richter Scale earthquake that occurred in Sabah
in 2015 was an eye opener , with 18 people killed in the earthquake ( Bernama , 2015 ). Since then progress has been made and in recent years the Malaysia National Annex to Eurocode 8 was released , which can be used as a guideline in determining the performance of buildings under seismic motion .
Earthquake damage is perhaps a more pressing matter to heritage buildings made from masonry compared to buildings made from timber , which tend to have good tensile strength . A limited study on heritage longhouses in Sarawak show that the buildings are expected to survive ( Hashim et al ., 2020 ) and any damage would be caused by the furniture and ornaments in the building , which might fall due to the building drift and cause injury . The resistance of the longhouse to earthquake damage was further improved due to the use of motise and tenon joints as shown in Figure 6 . On the other hand , the connections for heritage masonry buildings are mostly provided by mortar , which does not provide much resistance against earthquake damage , a problem that is further compounded by the weathering that the mortar may be been subjected to . Even a small amount of drift may cause a collapse of heritage masonry buildings ; hence the need to retrofit the buildings to ensure safety .
Guidelines for Assessment of Heritage Buildings
Several standards and guidelines are available for the assessment of heritage buildings , although most are related to a specific country . Some
42 VOL 85 JANUARY - MARCH 2021