In an objective to evaluate the surface burning characteristics of massive timber assemblies such as CLT and SCL, flame spread tests on massive timber assemblies have been conducted in accordance with ULC S102 test method. This study evaluated the flame spread of fully exposed massive timber specimens (i.e. untreated/uncoated) as well as the effect on flame spread by using intumescent coating with CLT. Test results provide low flame spread ratings when compared to those of common combustible interior finish materials provided in Appendix D-3 of NBCC. Specifically, the obtained flame spread ratings of 3-ply CLT assemblies of 105 mm in thickness are 35 and 25 for a fully exposed CLT (untreated) and for a CLT panel protected by intumescent coating respectively. Fully exposed SCL of 89 mm in thickness provided ratings of 35 and 75 for parallel strand lumber (PSL) and laminated strand lumber (LSL) respectively.