Fire gaps between buildings and household out-buildings on neighboring private plots are regulated in accordance with the technical normative acts (TNA) [1] and can make from 6 to 15 m depending on build-ing levels of resistance to fire. Fire gaps don't often follow these standards because of a number of factors. One of the security techniques of inflammable struc-tures is a gel application on the construction surface which is under thermal radiation because of the near vicinity of the radiation source. By means of a mathematical apparatus it is shown that using a layer of gel liquid 1 cm thick on a surface of inflammable structures and at direct impact of the thermal flow with 10 kilowatt/m2 density on a wood sample, sample ignition happens in 280-290 seconds after the beginning of influence. In the presence of a 0,5 cm layer of gel liquid ignition occurs in 140-150 seconds after the beginning of influence of the thermal radiation. Thus, the temperature value in a layer boundary with wood depends on the thickness of composition layer. When using a composition layer on the protected constructions made of wood we may avoid any spreading of the fire in nearby structures that will lead to minimization of material losses and considerable decrease of human casualties.