Timber Framers Guild Forums General General Forum Questions king post truss

JR:

Yes, I agree that the T&G looks best running opposite the common framing members. This was a case of the homeowner finishing the frame himself, and me assuming that he would do it the way I would :rolleyes: (hasn't happened since, of course ).

There were no structural issues, as the roof is made of SIPs. The paneling is only 1x6. CB.

Hi TB and everyone:

I will try and clarify if I can, sometimes what was done by the "old experts" is not easy to describe, but I know of examples standing today built in 1865 that is remarkably straight and true.

picture if you can your ring of upper plate timbers whether they are sitting on stone walls or vertical posts --no problem--now the bottom chord of each the trusses mortised into the opposing plates and pinned, or if you wish dovetailed and wedged. The top of each chord is flush with the top of the plate at the point of fastening

At a predetermined distance in from the plate the sloping truss timbers gracefully rise towards the peak from each end terminating , well mated and fastened at their tops, the bottoms are set into the top of the chord in a shallow seating and pinned securely.

In my example a 1" wrought iron rod drops down from the peak extending through the bottom chord to hold it perfectly straight.

Being that the truss is framed in a predetermined total distance from the extreme outer edge of the plate it allows enough room for the thickness of a squared timber to be placed on top of the sloping truss timbers (and listen carefully now) -these timbers are running the length of the building one on each side of the trusses and securely fastened there.

From underneath the sloping truss timbers and right where the aforementioned square timbers set an angled web supporting brace is gracefully set in place mortised and tenanted and pinned, (these braces are at a right angle to the bottom of the sloping truss timber).

Now all the rafters are set in mortises at their feet while their gently tapered lengths are supported about 1\2 the distance , to the peak, and lie above the trusses, what a sight!

this may not work for you and your plans, but variations of the above I am sure will work.

NH

nh: Still a bit confusing but I will re-read your reply until I get it. They used rods in the old days of tinber framing? I never heard of the use of steel(iron) on timber frames other than in more contemporary homes. You dont happen to have a photo of this truss/rafter system you talk about? thanks tb

TB,
You wanna see iron rods a bunch.
Many old railroad stations and maintenance buildings with timber trusses used iron rods a lot.
The old market in Charleston, SC, has very shallow roof pitch timbers and lotsa iron rods even thought some are only a couple of feet long.
Somebody may have pics.
Look around.

Hi TB:

this roof system that I am talking about dates to 1865, 2 years before confederation here in Ontario.

The rods are not steel they are wrought iron which looks similar but was formed using technology that was available in those days

unfortunately i dont't have any pics suitable for transmission on the internet, but have good ones on slides

NH

I believe the guild erected a hammerbeam truss structure in Sechelt BC. The span is 28 ft and if memory serves correctly it was the max it could be without additional structural support. i.e. buttresses. 10x14 doug fir posts also helped. Beautiful frame when finished. There were steel rods with turnbuckles added to cover any eventualities. The one on the first truss was my favorite!!

I have not seen the Sechelt building but if the rods connect hammerbeam to hammerbeam, the result is a queen post truss. I have seen that scenerio in industrial buildings from circa 1900 in West Virginia.

We put iron rods in there (I forget whether it was the architect or the engineer who required them).

They were a good idea, certainly, for the raising. We rigged them up to be adjustable ove a shortish distance, which proved to be a big help during assembly.

I think this can be done in an aesthetically pleasing way, and I am not embarassed to use them. Those rods are not a sign of failure, but rather a recognition that the hammer beam that they reinforce is being used outside of its natural habitat; the heavily buttressed masonry wall.

After all this talk about hammerbeams and iron rods my initial question still remains unanswered. I still am unsure whether it is even possible to construct a frame without a ridge beam but use the king post on one of the bents? Does the king post need a ridgebeam? thanks tb

No, a ridge is not structurally necessary to a King Post Truss.

Their presence in most frames is simply to provide nailbase, and simplify enclosure.

Though, this is not to say, a redundant lateral connection high in the frame is not a desirable thing.