Dangerous roof structure and practical solutions regarding rectification.
Faults with roof and danger. Potentially dangerous roof. These roof trusses are sagging considerably with separation of gang-nail plates (securings to joints between the web member and the top chord of the truss). QBIS
This very serious problem was unknown to the home owner/seller and required immediate attention!
Possible cause of roof truss plate separation.
Roofs move up and down in differing weather conditions. In particular, concrete tiles from water saturation that adds to the roof weight then dries out. With movement of the roof trusses this can cause the metal gang nail plates to separate over time.
Top chord of roof truss sagging.
Sagging chord also separation of gang nails to both sides of the roof truss.
Sagging chords are usually caused by lower grade of timber used when constructing the trusses, sometimes with knots in the timber that weakens it. Improper positioning of webbing can also cause sagging.
Sagging roof truss chord.
Different perspective showing almost full length of the truss. Indicating degree and severity of sagging to top chord also separation of gang-nails that secure the truss joints.
Some potential roof structure danger, causes:
- Insufficient securing of the gang-nails when the truss was manufactured.
- Differing weather conditions can also cause movement of the roof structure over the years.
- Not properly kiln dried timber used in the roof trusses.
This problem is less likely to occur with metal roof sheeting than concrete tiles due to much lesser weight.
How to rectify a potentially dangerous roof.
- Replace the roof tiles with metal roof sheeting.
- Have the roof structure secured for tying down.
- Reinforce the gang-nail plates.
Although some securing would be still required this would take a huge load off the roof structure and alleviate the necessity for restructuring the roof.
Worth knowing about roof trusses:
- Roof trusses are designed to allow for movement in normal weather conditions.
- Bottom chords are not usually designed to take loads unless specifically designed to do so, such as a cantilever.
- Extreme weather conditions can cause problems with roof structures when separation occurs, this would be dependent upon the degree.
Periodic inspections of roof structures and trusses.
- It is important to have your roof exterior and interior periodically checked by a professional.
- Securings of roof structures supporting metal sheeting are also important to have checked for tying down.
Early signs of problems can be identified and be rectified before they become serious and costly.
Beware of roof restoration companies that advise on roof structures:
Roof restoration companies are not qualified to check and advise on a roof construction condition and its required rectification. A competant experienced structural engineer must be consulted, otherwise your insurer may not cover you if a claim is made.