In order to improve the specimens' flame-retardant qualities, ethyl orthosilicate was impregnated into them using a combination of the delignification process and the in situ growing approach. Lignification has been demonstrated to increase the cellular gap of the specimen and to maximize the impregnation of ethyl orthosilicate. Moreover, the in situ growth method results in the combination of specimens containing silica manufactured from ethyl orthosilicate, thereby forming a composite material with enhanced flame-retardant properties. The examination of the changes in the properties of the specimens before and after modification was conducted using FTIR spectroscopy, XRD, XPS, SEM, and other experimental techniques. The modified specimens exhibited higher properties in comparison to the untreated specimens. Furthermore, the modified specimens exhibited enhanced mechanical properties, characterized by an augmented compressive strength of 34.9 MPa and a strength-to-weight ratio of 158 MPa·cm·g