The main objective of this study is to investigate the effects of rice husk addition on the porosity and thermal conductivity properties of fired clay bricks. Therefore, brick raw material and rice husk obtained from Corum, Turkey were used. Rice husk was substituted by volume (5%, 10% and 15%) to brick raw material in two forms as ground rice husk and coarse rice husk. The prepared mixtures were compacted in laboratory type extrusion under a pressure of 0.6 MPa for the perforated rectangular shaped (40 mm x 70 mm x 50 mm). Dried brick samples were fired at the rate of 2.5 degrees C/min until final temperature for 1 h. The observations during the tests show that bricks with the 5% and 10% addition of rice husk to brick clay exhibit a compressive strength of 7-10 MPa which is smaller than the reference clay bricks and nevertheless, satisfies the requirements in TS EN 772-1 and disaster regulation for a building material to be used in the indoor structural applications. Reference samples give the highest thermal conductivity at all firing temperatures. It has been determined that samples added coarse rice husk have lower thermal conductivity than samples added ground rice husk. (C) 2012 Elsevier Ltd. All rights reserved.