Analysis of typical defects in the waterproofing of inverted roofs of residential buildings identified during work acceptance

Abstract

The analysis of typical defects in the waterproofing of inverted roofs of residential buildings reveals persistent patterns of violation of the integrity of the waterproofing membrane, which determine a decrease in the operational reliability of structures under conditions of constant membrane contact with water and horizontal moisture migration between the layers of the roofing system. In systems with thermal insulation positioned above the waterproofing, which ensures protection of the membrane from ultraviolet radiation, mechanical damage, and temperature fluctuations but precludes subsequent visual inspection, the quality of acceptance of concealed works assumes critical importance, since overlooked violations lead to the need for costly dismantling of overlying layers and reduce the inter-repair period from 25-30 to 3-7 years. The distribution of 1247 recorded violations across 87 facilities demonstrates a concentration of defects in zones of junctions to vertical structures (33,44%), nodes of drainage funnels (16,28%), expansion joints (13,47%), and utility penetrations, where the average area of damage reaches maximum values, as well as on the roof plane. The structure of defectiveness is differentiated by material type: for bitumen-polymer welded membranes, blisters and air bubbles predominate (24,1%), caused by moisture in the substrate; for PVC, TPO, and EPDM membranes – defects of seams and joints (from 31,4 to 42,1%), insufficient overlap, and mechanical damage during installation of insulation, drainage, and ballast. An expert criticality scale ranks the risks, assigning the highest scores to the absence of funnel sealing (4.84), punctures (4.61) and unwelded seams, while the share of unremedied high-criticality defects reaches 9-40%. A strong inverse correlation was revealed between air temperature and defect density, which increases 2,7 times during the winter period due to loss of material elasticity and technological constraints. The obtained data substantiate the inconsistency of current regulations with the specifics of inverted solutions and the advisability of implementing risk-oriented control, continuous instrumental testing, intermediate monitoring after installation of each layer, and updating of the regulatory framework. This approach allows a significant increase in the durability of coverings and minimization of economic losses from premature repairs in residential construction.