Collar ties

[tbear]

My brother and I are building a 16x24 shack and he believes we need to use collar ties. I'd prefer to have nothing like that between the evaporater and the cupola. My concern is condensate forming on the collar ties and dripping back into the pan. I understand the need for the collar ties but is there a way to avoid them under the cupola? Thanks, Ted

[claystroup]

You should be fine if you leave the collar ties off under your cupola. You could put a double collar tie on your 2 rafters that fall at the ends of the cupola opening for added strength.

[tcross]

you could use a structural ridge beam and not need any collar ties! you'd have to beef up the rafters framing out your cupola and beef up your ridge beam. I'm not sure how you're framing it up, but something like 3 2x12's or 10's rafters framing up your cupola and the same for your ridge beams.

[VTnewguy]

If you frame out your space for the cupola you will have a section with out the collar ties.

[phil-t]

Collar ties hold the walls from spreading, under load from the roof/rafters. Build your top wall plate to support that (outward) load from the rafters. Unless the cupola is the entire length of the 24 ft. building, the sizing of that plate should not be too bad. When I built mine I used two 2X10s on ege and two more, flat ways, to form a "box" for the plate. No problems.

[wmick]

Structural ridge beam needs to be supported vertically on posts, etc.. (at ends if a continuous single beam).... (or intermittently if too long... or broken up by things such as cupola cut-out)... dont think that will be your solution for a 24' long building.???

How long is your cupola going to be?? If not too long you could frame the sides (where it ties into the rafters) strong enough to resist the lateral spreading... and collar tie the rest of the building.

Heres a pretty good link that explains the need and some design tips.
http://inspectapedia.com/structure/Roof_Framing_Specifications_Canada.php

[Zucker Lager]

Planning my own cupola and I"m thinking the same about beefing it up to handle the stresses without crossing the opening so I'm thinking of using a double rafter on each end of the cupola opening then using two fitch plates for the sides (headers) made from angle iron and wood to take both the vertical and horizontal loading and tie the short rafters into the fitch plates. Bolt both ends of each fitch plates into the double rafters on each end. Would be nice to have that open area with no clutter like Ted wants. thanks Jay

[maple flats]

I have trusses the whole length at 24" on center, except the space is 32" on center at the stack then a narrow one to get back on the 2' spacing. As such I have trusses in the middle of my cupola, between those trusses are my 2 steam stacks which terminate in the cupola. I don't seem to get any steam building up on those trusses nor do I get drips falling on my hoods. The only heat in the sugarhouse other than in the RO room, is the arch.

[Shaun]

Possibly you can tie the top plates of walls together with a 3/8 cable if you are worried about wood getting stained ETC.

[Spanielslovesappin]

There are many ways to skin this cat but you must do something to tie the walls together to keep them from spreading. Condensate dripping off the collar ties will be no worse than it dripping off all the rest of the structure above the evaporator thus the use of hoods. That said you can likely skip the ties in way of the cupola if you substantially build up the rafter/tie sets at each end of the cupola. Wire is always an option to hold the walls together if you are looking for a more open feel.

[tbear]

Thank you all for your responces! Ted