cathedral ceiling in my cabin

fred klose

I have a cathedral ceiling framed out of 2x6 on 16 inch centers,2x8 ridge beam span 28 feet from gable to gable.length of rafter is 12 feet from ridge to top plate 3 feet down from ridge is a 2x6 on both sides of the rafter making a collar tie these are every 4 feet roof pitch is 10/12.Floor joists run oposit of roof rafter is this ok.will my walls push out?if so what can I do. This is a cabin I built 3 years ago

fred klose

back wall in cabin with cathedral ceiling

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fred klose

Back of cabin you can see where collar ties are

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mics_54

What are you going to do at the edge of the loft floor? A rail wall would help tie the two sides walls together. Will there be no other interior walls on the upper floor?

The chances of the walls spreading looks pretty good with no other means to keep them vertical.

fred klose

I have a spiral stair case in the right corner with a hall coming to the back gable so I could not run wall all the way across loft also had not planed on interior walls in sleeping loft do to back window veiw

fred klose

first pic shows windows from under loft and spiral is in the left from this view you can see outside band of hall in upper left corner.Which will also have hand rail.

fred klose

Front of cabin was going to be porch but I closed it in note 6x6 run two sec story tying walls in.

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fred klose

New front of my cabin with porch

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Gary in WA

You need an engineered structural ridge OR rafter ties at the top plate 4' on centers. This is very dangerous.
Be safe, Gary

fred klose

I do have simpson rafter u ties at the and of ever rafter is this what you mean and are the collar ties doing nothing.Very dangerous how so do you think there is a real sign of danger would I not see signs of cracks in dry wall finsh and paint?Also I put the ties on the outside with simpson nails.rafter tie model rt 15 usp NO BIRDS MOUTH!

Gary in WA

Hi, again, Simpson H-1's are to connect the rafter to the house in a strong wind (up-lift). Collar ties are to reduce the rafter's span, but they must be placed midway or higher(if needed) to balance the roof in compression. Read this: http://books.google.com/books?id=1fI...20ties&f=false

Rafter ties are to keep the walls from spreading, or ceiling joists at the plate line (end of the rafter).
Sec. 2326.12.6. Rafter ties. Rafters shall be nailed to adjacent ceiling joists to form a continuous tie between exterior walls when such joists are parallel to the rafters. Where not parallel, rafters shall be tied to 1-inch by 4-inch (25 mm by 102 mm) (nominal) minimum-size crossties. Rafter ties shall be spaced not more than 4 feet (1219 mm) on center.
Sec. 2326.12.7. Purlins. Purlins to support roof loads may be installed to reduce the span of the rafters within allowable limits and shall be supported by struts to bearing walls. The maximum span of 2-inch by 4-inch (51 mm by 102 mm) purlins shall be 4 feet (1219 mm). The maximum span of 2-inch by 6-inch (51 mm by 152 mm) purlins shall be 6 feet (1829 mm) but in no case shall the purlin be smaller than the supported rafter. Struts shall not be smaller than 2-inch by 4-inch (51 mm by 102 mm) members. The unbraced length of struts shall not exceed 8 feet (2438 mm) and the minimum slope of the struts shall not be less than 45 degrees from the horizontal.

Be safe, Gary

fred klose

confused, Do I need to add ties at a lower elevation.Pitch is a 10/12 so this is good right for more downward weight.To add rafter ties on top of wall top plate is out of the question. It would only be 4 foot high off loft floor.What to do?thanks

fred klose

Can I do something with loft floor or band to help tie in walls.thanks

fred klose

Or simply add any addition on both sides with shed roofs this would tie the whole structure in right please help good or bad idea. Thanks cant send gbr private message yet

Daniel Holzman

The fundamental issue with the framing is that there is almost nothing to prevent spreading of the outside walls. Normally, there are floor joists spaced approximately 16 inches on center, the joists are attached to the outside walls, AND the joists are nailed to the rafters. When the rafters carry vertical load, such as snow, the rafters tend to spread outward. In your case, it appears that the rafters are several feet above the floor joists, and are not connected to the joists.

If the rafters are attached to the joists, the outward force generated by the rafters is carried by the joists in tension, NOT by the walls. The walls are not structurally capable of carrying spreading loads, they will deflect causing no end of trouble. I inspected a house in New Hampshire that had improper connections between the joists and the walls, and weak connections between the rafters and the joists. The result was outward movement of over three inches at the top of the wall, causing serious structural damage to the house.

When designing a house with no joists to tie the rafters in to, it is necessary to provide an alternative method of carrying the thrust load of the rafters. One possible technique is to install a ridge BEAM (what you have is a non-structural ridge board). The ridge beam is a structural element designed to carry approximately half the vertical load of the roof by supporting the rafters. The other half of the vertical roof load is carried by the walls.

A ridge beam must be designed to carry the vertical roof load, therefore aside from being a major structural element, it requires adequate supports on either end, or possibly a column in the middle as well. Because a ridge beam supports the rafters at the top, preventing movement of the rafters, the rafters do not generate outward thrust when loaded by snow or wind. However, the rafters must be properly connected to the ridge beam, which is an entire chapter in itself.

The collar ties you installed appear to be in the upper quarter of the roof, and may not be adequate to resist lateral loading. You should have the design evaluated by an engineer familiar with the loading in your zone, including wind and snow. Your local building inspector may have some insight as well. My experience with collar ties is that they almost never provide adequate support BY THEMSELVES to resist thrust generated by rafter spreading, they are useful when combined with floor joists to carry horizontal load.