In older homes that were what we call “stick-built,” finding roofs that sag a bit is not uncommon.
Sometimes this sagging is cosmetic–other times repairs are called for to prevent actual collapse of the roof.
As you can see in the following picture this old horse had quite a sag in half of the roof (from the chimney to the end of the house). The portion that was not sagging was over the vaulted kitchen and living room areas–and was well supported by an adequate beam for the span. The back half of the home, where the bedrooms and bathrooms were, was framed conventionally with a ridge board and rafters. The ridge board was made of two pieces that butted together in the middle. In this type of framing, the ridge board should not be relied upon to carry the load of the roof anyway. Inadequate attachment of the wall-to-wall supports has allowed the ridge to sag. Intermediate supports of the ridge, a proper ridge beam and/or adequate restraint from wall to wall could have prevented this sagging. The sagging you see in the ridge resulted in corresponding bowing out of the walls on both sides of the home.
So for 50 years this roof has been settling–a little more every year just under its own weight, seasonal snow loads and additional layers of roofing materials.
It is not unusual to have unsupported ridge boards. About all the ridge board does is to give the builder a way to assemble the rafters and to space the rafters. It would be “possible” to build the roof without a ridge board–just like we do with trusses which have no ridge boards–but it would be considerably more difficult. Once the roof is sheathed and the framing is complete the ridge board really does not serve much function and is not typically relied upon to support the roof structurally.
This is all especially true of roofs that are fairly steep—like 6/12 and steeper. These roofs will usually have collar ties and/or intermediate knee-wall structures to assist in supporting the roof to resist sagging. As roofs become flatter these intermediate supports become even more critical and in most cases you would probably want to support the ridge board to prevent sagging.
It is not rocket science that this very low pitched roof needed more support–and fortunately will not be that difficult a fix for any experienced framing contractor. The roof was leaking at the time of inspection so making repairs in conjunction with the roof replacement was recommended.
This old horse was not really ready for the glue factory–or even to be put out to pasture after all.
Now if you want to see a horse that IS ready for the glue factory take a look at this next picture.
This shed at a neighbor’s house, near where I live, had looked like this for at least 18 years–leaving me to conclude that a garbage can on top of Grandma’s old Desoto sedan must be what is holding up the roof. The building is now finally gone–it disappeared one day when I wasn’t looking. I have no idea if there was actually a Desoto in it or not.
By Charles Buell, Real Estate Inspections in Seattle
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