Ridge Beam Structural issue? 5

[amorphous12]

Hello,

Apologies if this is the wrong forum, but I thought someone here might be able to provide an opinion. Looking at a home and underneath the ridge beam I've noticed a slightly jagged horizontal crack a little longer than the width of the ridge beam (photo attached - listing photo was photo shopped so I'm unable to show the actual crack). It is probably less than a quarter inch thick. The inspector mentioned this was probably just settling since this is where 50% of the load is supported, but I'm wondering if anyone thinks this is a larger concern?

 

[Ron]

Many inspectors attribute most cracking they see to "settlement". Not so. Settlement cracks present in certain ways...this is not one of them. This is likely a shrinkage crack resulting from differential drying shrinkage of the construction materials. You have drywall abutting wood in different directions and planes.

Fill the crack with latex sealant (commonly known as painter's caulk) and paint over it. Done.

 

[oldestguy]

Ron may be correct. However, if this roof gets a lot of sun, the roof may expand and contract daily, with the rafters pushing up. The wall studs are likely in the shade and don't expand lengthwise. Maybe a combination of both wall shrinkage and the effect of sun on roof.

Us Yankees also know the effect of temperatures when the sun goes down on a cold winter night and we hear the loud cracks of the roof as it shrinks.

 

[msquared48]

If this is a newer home (a year or two), I would agree with the comments above..

However, if this is an older home, and the crack was just noticed, something else could be going on here.

I would ask:
1. How old is the home?
2. Where are you located?
3. On what is the column that supports the ridge beam bearing?
4. When was the crack first noticed?

May be nothing. Just wondering...

Mike McCann, PE, SE (WA)

 

[amorphous12]

Hello msquared48


I would ask:
1. How old is the home? The house is 16 years old (2002)
2. Where are you located? (North East. We have four seasons, heavy snow fall in the winter)
3. On what is the column that supports the ridge beam bearing? (not sure I understand this question)
4. When was the crack first noticed? (buying the home so I don't know how long it has been there, it seems as though it has been photo-shopped out on the listing or happened after the picture was taken) I've attached another picture for reference.

 

[dhengr]

I think that the vegetation growing on the wall below the beam has consumed all the moisture and has caused some subsidence in the wall.

 

[oldestguy]

mssquared has opened a can of worms. I'll add my worms. That so called beam up there does nothing structurally and does not need to sit on a column. For all practical purposes it only serves to provide a place for rafters to lay against in a line when building, for all for rafters to not necessarily be aligned across from each other. I did the same thing when I added an addition to my log house. Matter of fact my "ridge beam" was not long enough for the addition,so I spliced in another with a simple lap joint. It does not carry any load. All the load is carried by the bottom ends of the rafters. Any uneven wind load goes thru that beam across to the leeward roof side. Uneven suction loads are carried across via the nailing at the ridge area ends of rafters, via that "ridge beam" , It could be just a 2 x 12 doing the same thing.

 

[oldestguy]

OG again: My undergrad and grad days were spent in Lincoln Hall At Cornell. I can assure you there were no columns supporting those many ridges.

 

[amorphous12]

OG, appreciate your opinion. According to the diagram attached, it is stating that 50% of the load is supported by the ridge beam/post? That seems to disagree with your statement re:rafters and load?

 

[msquared48]

Ok. Since you do not know the age of the crack, just patch as Ron suggested and monitor

If the crack opens up again, contact a local structural engineer.

The beam probably rests on a column that rests on a header over the window below.

Mike McCann, PE, SE (WA)

 

[CANPRO]

oldestguy, that could be the case if you had collar ties. You need a structural ridge beam, or some form of lateral restraint at the connection to the wall. There doesn't appear to be any collar ties, ridge beam likely structural.

 

[oldestguy]

I have no problem with the diagram showing support via a ridge beam. HOWEVER, for the case in question and the references I made the roof slope is a rough 60 degrees above the horizontal. At Cornell the "attic" wall is an equilateral triangle with the 60 degree above horizontal for the roof slope. So I ask at what slope of the roof does one have to have to avoid that ridge beam? Suppose the slope is 75 degrees or more above horizontal. You guys would still use a ridge beam? That old Lincoln Hall at Cornell now is well over 100 years old and still in use. I'd like to hear what my German immigrant Prof Winter would remark if he were here, Wow.

So don't put low,slope roofs into this case with a steep roof.

S o far no comment from me on the eave loads from the rafters. Yes, the outward thrust down there must be carried.!!

 

[civeng80]

A window is directly below the ridge beam and and the lintel supporting the stut may be deflecting a bit more than allowable, thus abit more settlement in the ridge beam.

 

[oldestguy]

amorphous: Time to sit back and have some fun. Fill in the crack, paint over it and put your attention to more important things. One would be getting that supply of goodies ready for the trick or treaters. They pose more of a problem for you than the roof.

 

[XR250]

I'll add my worms. That so called beam up there does nothing structurally and does not need to sit on a column.

OSG:

No offense, but you are incorrect. If there are no rafter ties/ ceiling joists at the appropriate height, the rafters need a vertical support at the ridge to mitigate their thrust at the wall - unless the wall is designed to resist the thrust (unlikely).

 

[IceNine]

I agree with oldestguy...if the roof is steep enough and has sheathing, it will act as a diaphragm with the thrust being resisted by the end walls, like a folded plate.

 

[XR250]

I agree with oldestguy...if the roof is steep enough and has sheathing, it will act as a diaphragm with the thrust being resisted by the end walls, like a folded plate.

Yes, you could make that work on a small roof if you were diligent about the details. I have seen builders try that 20 years ago and now I get to have fun designing retrofitted ridge beams to fix the flared out walls.

 

[msquared48]

We discussed similar problems in another thread about two or three years ago I believe. Can't find it right now.

Oldest guy does have a point here. This situation involves the deflection interaction of a Ridge beam and two plates os different slopes, and the connections of those same plates to the exterior walls.

But for now, just patch and moniter.

Mike McCann, PE, SE (WA)

 

[oldestguy]

XR250 The way my log house roof and many of the neighbors handle the horizontal thrust of the rafters(and likely Cornell's Lincoln Hall) is the floor at the eave level gets the tension. Stagger the flooring, tie the joists at the center,etc. and there is no bulge of the wall. In addition the diaphragm effect of the sheathing plywood also provides a significant bending resistance in the plane of the roof. It is a system all providing a combined effect of all units. Not taught in beginning structures courses. Matter of fact of the many structures courses I took it was not mentioned. A very indeterminate situation also, but it works.

Edit: Then add to it the bending resistance of the floor in the plane of the floor (joists across, boards parallel to the eaves and wood flooring on top in the direction of the joists.

 

[XR250]

Like I said, it CAN be made to work. I have seen enough of these "not work" in practice that I would never design one without a structural ridge unless there was a super compelling reason to do so. I am working on one right now where the walls are splayed 2" and the new homeowner is suing the building inspections department for letting the construction pass.