A durable composite sheet is provided, with a method of manufacturing the composite sheet. The method includes using a crack-resistant reinforcement panel between a gel coat and a reinforcement panel, which may be of lauan or of other materials. At least one outer coat of material is applied onto a mold surface. A barrier layer may be formed on the outer coat, preferably by spraying. At least one coat of a resin material, containing a curable resin and optionally a filler, and a fibrous reinforcement material are applied over the outer coat (over the barrier layer if present) to form a reinforcement layer. The reinforcement panel is applied to the crack-resistant reinforcement layer, and is bonded thereto.