A ridge that droops in the middle forming that unintentional western design feature likely is due to undersized rafters and or missing or inadequate internal bracing rafter or collar ties.
Roof bowing in the middle.
One of the most common causes of roof issues are problems related to the rafters or trusses.
Curling shingles also referred to as fishmouthing is when asphalt shingles have curled on the ends and appear to be bent or twisted.
They have issues for a wide variety of reason including damage from wind storms overloading from ice and snow leaks etc.
Read on to find out what you can do.
There are different reasons and types of curling.
Therefore giving them a good look is critical when addressing sagging bowed or wavy roofs.
Repairing a roof rafter in this condition is not a hard project but it can be difficult if there is not easy access.
If your rafters are still sagging a bit and it is causing your roof to dish out a little in the center of the roof sides add a 2x4 that goes all the way across the rafters in the center of the length of the rafters.
That s why most of the ridge sagging occurs in the center of the roof page top photo.
Use your string line to determine how much the roof need to go up.
What causes a sagging roof line.
If you notice that there is a visible dip in your roof chances are you have a problem with one or several rafters and you may soon be facing more issues like water leaks bowed out walls or your roof caving in on you.
It might be something.
It is more common than you might think for a concrete block foundation wall to bow inward and repairing the problem is a tall order even for an accomplished do it yourself homeowner.
Installing new rafters directly alongside the weak or damaged ones is often enough to correct this problem.
In a stick frame non truss sloped roof these issues usually cause the roof ridge to sag in the middle giving it a swayback look but can also cause one side of the roof to sag.
If you can see a dip curve or swag on the peak when standing in the street your roof has a problem.
This often occurs in the middle of the shingle tab.