<p>Ceiling boards are highly needed in our daily lives due to the need for temporary ceilings in the construction industry. However, the use of ceiling boards in Uganda is affected by climate fluctuation, with a dominant wet season throughout the year which leads to damages to existing ceiling board materials such as cardboards and plywood. These ceiling boards also have low durability, low fire resistance, hence their limited usage in the construction industry. This study has developed a material for ceiling boards that offers suitable mechanical, physical and thermal properties using rice husks as a filler material and polyethylene terephthalate (PET) plastic residue as an adhesive. The study aimed at investigating the effect of raw and treated rice husks composition in PET plastic residues for the development of composite ceiling boards. The ceiling boards were processed using varying amounts (10–30wt.%) of raw rice husks (RHR) and NaOH treated rice husks (RHT) by melt-blending with PET flakes. Fourier Transform Infrared Spectroscopy (FTIR), density tests, water absorption tests, thermoconductivity and mechanical tests were carried out. The functional groups present in raw and treated rice husks composites are predominantly the same, including O–H, C–H, C=O, and C–O groups characteristic of cellulose, hemicellulose, polyesters and lignin with slight change in intensity and sharpness on FTIR spectra graphs. Treated rice husks-PET ceiling limited board composites (RHT30) are better than raw rice husks-PET ceiling board composites (RHR30) for the ceiling board application due to the less water absorption rate 4.23%, lower density 140&#xa0;kg/m³. The treatment process of the rice husks affected their compatibility and adhesion with PET, resulting in lower mechanical performance.</p>