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RE: Use of Collar Ties in Light Frame Wood Construction

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While I would agree, collar ties are still being used in conventional
construction. In this case, the collar ties would not be the primary lateral
restraint system of the rafters - this is already accomplished (albeit not
too well considering the drop in the damaged ridge board) by the ceiling
joists which are used as rafter ties. I really have nothing else to brace
the high roof ridge to unless I design one beam at the ceiling to act as a
ridge beam - and this will require new foundations.

Dennis

> -----Original Message-----
> From: chuckuc [mailto:chuckuc(--nospam--at)pacbell.net]
> Sent: Tuesday, June 05, 2001 1:09 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Use of Collar Ties in Light Frame Wood Construction
>
>
> I seem to recall an intersting discussion in a recent JLC to the
> effect that
> collar ties were a bad idea.
> Chuck Utzman
>
> Structuralist wrote:
>
> > I have a client with a home in escrow. There is a cracked ridge
> board in the
> > garage and it appears that the ridge has dropped a few inches.
> The framing
> > is rafter tied by the 2x6 ceiling joists to the 2x8 roof
> rafters, the ridge
> > board is a 2x12 DF. The crack in the ridge board is parallel to
> grain which
> > runs diagonally through this section of the board - an obvious defect in
> > material not found during original construction.
> >
> > I intended to jack up the roof and install 1x6 collar ties at 1/3 the
> > distance down from the peak of the roof. The attic is
> accessible to install
> > the collar ties and all other existing framing looks pretty good.
> >
> > The 2000 IBC lists the use of 3-10d nails to secure the 1x to
> the rafters.
> > However, this 2000 IBC is not used in California and collar tie
> nailing is
> > not indicated on the 97 UBC Nailing Table. The only reference
> to collar ties
> > I could find was in Appendix Chapter 23 - Prescriptive Masonry
> Construction
> > in High-Wind Areas where Section 2112.10.2 states: "Gabled and
> sloped roof
> > members not supported by the ridge shall be tied by ceiling joists or
> > equivalent lateral ties located as close to where the roof
> member bears on
> > the wall as is practically possible, at not more than 48 inches
> on center.
> > Collar ties shall not be used for these lateral ties."
> >
> > Now I am at a loss. In my opinion (as this was a common form of
> construction
> > for many years) collar ties are ideal to resolve this situation but this
> > condition requires them to act as lateral support. The existing
> ceiling ties
> > obviously help, but are not restraining all of the outward thrust of the
> > rafter tails since the ridge board cracked. Installing a Ridge
> beam seems an
> > inappropriate solution here as it would redistribute the roof load and
> > require the possible addition of two foundations at each end - requiring
> > that we cut through one slab and underpin the exposed slab edge.
> >
> > Any suggestions or information that would help me justify the
> use of collar
> > ties?
> >
> > If I still use collar ties (assuming the building department
> accepts the fix
> > as I suspect they will) I intended to install a 1x6 on each
> side and face
> > nail each end to the rafters with (3) 10d nails - spacing the
> collar ties
> > every other bay or 48" on center.
> >
> > Regards,
> > Dennis S. Wish, PE
> > Structural Engineering Consultant
> > mailto:structures(--nospam--at)engineer.com
> > (208) 361-5447 E-Fax
> >
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