![]() ![]() Ridge sag is called “deflection” by construction professionals and is easy to spot from the ground when in an advanced stage, but minor deflection is best caught by sighting down the ridge of the roof. The house shown below is an example of this problem: ceiling joists were removed to create a higher ceiling and add a shed dormer window, without additional reinforcement.Ī tie in the upper two-thirds of the rise is called a collar tie which, although it adds some rigidity, is too small to create a strong enough triangle to resist spread. If the ceiling rafters are removed to “open up the ceiling” in a renovation, ridge sag will occur unless some other form of triangulation is added-such as rafter ties added within the bottom third of the vertical height (rise) of the roof. ![]() The ridge board provides a stable nailing surface and adds some lateral stability, whereas a ridge beam is a structural support member that eliminates the need for a connection between the end walls to avoid spread. ![]() Although not shown in the diagram below, they are often actually two pieces of lumber joined together over an interior wall or beam.Ī ridge board or ridge beam at the peak of the roof is also an important component. Most houses that have a roof framed with rafters use ceiling joists that connect across the house between the bottoms of each pair of rafters to form the necessary triangulation. 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. But a rectangle can be deformed into a parallelogram by any load that causes rotation at the connections, and shapes with more than four sides can similarly be deformed at their connecting points. The unique property of a triangle is that it cannot be deformed as long as all three sides remain intact and connected. He won't be fast, but itl be right and he won't have to break your bank.Sloped roofs with a ridge depend on the inherent strength of a triangle to create a sturdy roof. This house can definitely be fixed structurally for material wise around $20,000-$40,000. All carpentry (framing, trim, cabinets, windows, siding, doors, fireplace mantles, bookshelves, closets, etc), flooring (wood, laminate, tile, vinyl, etc.), Showers, install fixtures and appliances, paint, etc. I do outsource electrical, roofing, and plumbing. it cost $86,000 and change to completely update, renew, and make handicap accessible. The home was at least 100 years old, and when I started taking out sheetrock, I saw that according to the framing, was originally a 10×15 cabin that had been added onto at least four times to a single-story home of 18,000 sq.ft. The most expensive one I did was for a husband and wife who were both eye doctors, and had handicapped children. I'm basically convinced that most contractors are simply liars, because I have at least six times in the last ten years completely remodeled an old (60- 100+ years) home for far cheaper than a market-value new home of equal side. I remodel old homes that nobody else wants to touch all the time. Why does everyone act like everything is so complicated. It is possible to keep the dormer feature, but not as it's currently framed. The repair sequence will likely involve removing the dormer entirely, jacking the ridge, moving walls back into plumb, then reframing new structure to carry the load paths down to the foundation. The amount of sag here is pretty serious, I'd be concerned that eventually there will be a partial collapse of the roof. What will it take to fix? Quite a bit, starting with an engineer. Without the pairs of rafters to tie into the rafter ties at the bottom there's nothing to prevent sagging of the main roof. As others have surmised, it's almost certain that the dormer was added, and in the process the rafters were cut out at that location in order to finish the space. Here's some more detailed info on the way roof structures are framed, and why:Ĭollar ties are used in the upper third of the rafters to protect against wind-based uplift wanting to split the roof at the ridge, and rafter ties are used in the bottom third (typically at the very bottom) to prevent sagging and spreading from roof loads.
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