Abstract: A roof construction having at least one roof slope is disclosed wherein at least four Z-purlins are laid across and secured to a number of rafters on the roof slope in a building and the roof deck is then secured on top of the Z-purlins. Tendencies toward Z-purlin roll over failure are counter balanced when at least two of the Z-purlins on the roof slope are oriented to face downwardly of the roof slope and at least two of the Z-purlins on the roof slope are oriented to face upwardly of the roof slope. The downwardly and upwardly oriented Z-purlins may be arranged in pairs of adjacent Z-purlins, each pair comprising one upwardly and one downwardly facing Z-purlin, or so that Z-purlins of one group face upwardly and Z-purlins of the other group face downwardly. The Z-purlins are stabilized by means of stiffeners secured to the purlins at bearing points and by means of tie straps extending between adjacent purlins.