The use of timber as a structural material in multi-storey buildings is often limited due to its combustible nature. The fire performance of the wooden members can be determined through the standard fire tests or, more often, using the calculation procedures recommended by the design codes. The fire resistance of a timber beam can be calculated based on the residual section without taking into account the charred area and the zero strength layer. However, the zero strength layer (d0) it is assumed to be a key parameter of the fire design of timber members. Recent studies show that the utilisation of d0 may be non-conservative in some applications and the simplified design approach method may not properly describe the complex behaviour of the timber members exposed to fire. The paper presents an experimental research on a loaded glulam beam (GL24H) exposed to the standard fire on three faces. Heat transfer and mechanical behaviour of the beam is estimated by simplified reduced cross-section method according to Eurocode 1995-1-2. The experimental charring rates are compared with theoretical and notional values.