Ken -

I had to click the 'filmstrip' image and then save. I also had to manually change the name of the file after I downloaded - there were underscores before the file name and after the '.mov' which had to be removed.

Very very cool Quicktime VR photo.


That is a ton of work to create that roof!
And it looks like there are some spreading problems - I see steel rod and some extra bracing in that photo.

Hi Mike,

You can be forgiven for thinking that there is a forest of wood in that roof but as I recall when I calculated the volume of timber there was only about 750 cu ft used to cut the whole roof which has an internal span of 20 feet, external span of 26 ft and length of about 56 feet. This roof has double wall plates with a corniced flying plate and ashlars. The timbers are so dense that it's almost impossible to see the rafter peaks.

The main reason for the movement in the roof is probably down to the insertion of a 3 flue chimney which cut through the wall plates on one side and hence also through some of the scissor couples. In due course the chimney was removed and the roof yielded. This roof is in a castle and it has a number of other roofs intersecting and leaning upon it which also add to the deformation and yet at the same time provide a little more longitudinal stability. The roof was originally plastered over the 7 internal cants and presumeably this must have started to fall off centuries ago due to the various deformations. The original barrel valuted ceiling was then torn down and a new suspended ceiling inserted at tie beam height. This removed more than half of the longitudinal stiffening for the roof since the external tile battens are set at 4" spacing whereas internal lath is probably set at about 2" spacing. The metal tie rods are interesting in that since each of the scissor couples are independant i.e. no purlins then the metal ties will tend to provide only localised point load type pulling on the rafters and then rely on the external tile lath to transfer this restraint to the rest of the roof.

Inspite of all this abuse the roof still survives as a very early example of the kind of roof under discussion.

Regards

Ken Hume

Hi Mike,

Re file download :-

I should have referenced the following link :-

http://cid-a449afe501ee8113.skydrive.live.com/self.aspx/Movies/Bishops%20Camera%20Roof.mov

Regards

Ken Hume

Hi Guys,
Been on vacation the last week, but just wanted to pop in and let you know I'm still here. I'm enjoying the conversation and learning as I go.
I'm going to have to put this garage on the back burner for a while (which will give me more time to consider how to frame it anyway) since the fuel delivery guy somehow set fire to my diesel and gas tanks today and burned down their shed. Thank the Lord the tanks did not explode and no one was hurt. Now I have to rebuild that also.
I am also trying to learn a bit more about the Google Sketchup.
However, I will go ahead and cut my beams and get them ready. I think the consensus was that 8x8's would probably work, with maybe the 24footers being 8x10's.
Later
Ben

you could easily replace the 24' plates with sliced 12 and 14' members if you are trying to use timbers you already have available. however, i have never seen a spliced ridge so that would still leave you with 4 24'. im jumping in late in the discussion but ive read most of the thread and i would have to agree that the kp is necessary to carry a 24' span. also some were talking about removing the ridge beam but the only cases that i deem ridge beams unnecessary have principle rafters at the roof level. removing the ridge beam would also leave the tops of the trusses suspended in mid air and put rotational stress on the main ties.