Old Roof Support System Inspect Purlin

Dale nelson president of roof hugger left with red mcconnohie the product s inventor.

Old roof support system inspect purlin.

The support system for the roof is comprised of ridgepole and rafters or purlins. The use of purlins as opposed to closely spaced rafters is common in pre engineered metal building systems and both the ancient post and beam and newer pole building timber frame construction. For heavier material such as gage steel the metal roof purlins spacing length could go up to 4 feet. Photo above is from a jwk inspections framing pre drwall inspection in the san antonio south teaxas area showing the actual roof framing componenents.

A higher pitched roof would be better for extra living space than a lower pitched roof. They are lapped 48 over the supports. New panels being installed over roof huggers on an old roof above. A great deal depends on the pitch of the roof.

The c purlins are not welded. Purlins are not required or needed unless rafters are overspanned and then the purlins serve as support to prevent roof sag deflection due to the overspanned and or undersized rafters. This is where a high pitched roof is necessary. Many single ply membrane roofs rely on the existing metal roof to function as a structural deck for support and attachment of the roof system including board insulation as well as for support of live snow and wind.

Ply roof systems are also lightweight and utilized for retrofits over existing metal roofs figure 2. The typical spacing standards for residential and commercial buildings are about 1 to 2 foot. Collar ties rafter ties tension beams structural ridge beams. Conventional roof framing and roof trusses.

The other is just used to support the trusses. Purlins support the loads from the roof deck or sheathing and are supported by the principal rafters and or the building walls steel beams etc. We won t go into attic inspection too deeply since this series of articles from mastering roof inspections is primarily about roofing defect recognition but you should have an understanding of the two main basic roof structure systems. Some of these can support the roof and prevent ridge sagging and wall spreading.

Between the lapped c purlins is a 16ga. Once again a 2 by 4 inch piece of lumber is placed between the trusses and parallel to the ceiling joists. The plate is sandwiched between the c purlins and is attached to the top flange of the support girder. The roof purlins are 9 deep 16 ga.