Sagging Ridge Line On Roof

When the roof framing is assembled two ceiling rafters are often joined together to create a longer span.

Sagging ridge line on roof.

If the line does not continually follow the bottom of the beam and the bottom of the beam is below the line the beam is sagging. When the framing of the roof is put together quite frequently two of the ceiling rafters will be fixed together as this will create a much longer span. A sagging roof line may original from the ceiling s horizontal rafters. Sagging rafters may be the result of having framed the roof with lumber of dimensions smaller than current building standards such as using 2x4s or 2x6 s or there may be damage to the framing from insects or rot.

When the roof joints and rafters are improperly constructed this can lead to a sagging roof later on. As the roof ridge sagged downwards red line and arrow the centers of the front and rear walls of this little house bulged outwards telegraphing that movement into the outwards lean of the front porch as the front walls of the home also pushed the porch roof outwards blue line and arrow. Sagging roof lines can originate with the horizontal ceiling rafters. Typically they are lapped and then toe nailed together in its center so that the correct length can be achieved.

The base of the triangle forms the ceiling or roof joints while the rafters are the diagonal walls that slant toward the ridge line. There weren t any particular indications of this occurring. Ridge beam or ridge board sagging or damaged roofs may sag because a ridge beam or ridge board is cracked or damaged. The most common cause of sag at the roof ridge is loss of triangulation due to failure of the bottom leg of the triangle which makes the peak of the roof sag and top of the walls spread outward in the area of failure.

Think of your roof as a triangle. When properly designed the loads in a rafter roof design transfer the loads down as well but when the ridge beam is undersized it will sag causing the rafters to exert lateral pressure on the perimeter walls. The first step is to the basement first. And then there is the puzzle of the vaulted ceiling.

So you should start by inspecting the roof from the under side or attic.