Frame design for hip and valley roof needed

canopy · January 08, 2010, 07:27:27 PM

I wish to build a single story rectangular building with a long eave overhang plus a hip and valley roof. This will be a primer before building a house using the same design on a bigger scale. I have read a number of timber framing books and searched the net, but have not found a frame design that covers frames suitable for hip and valley. Can anyone help provide info on an optimal frame design? Even very basic practicalities such as where to position the posts is appreciated. A little about the structure:

Outer building dimensions not including eaves: 3.5m x 2.5m

Eave overhang on every side: 1m

Roof pitch: 17 degrees or greater

Roof weight: 70kg/sqm (clay tile)

Location: Thailand (warm-hot year round)

shinnlinger · January 08, 2010, 09:09:00 PM

Hi,

I ran over a 3 foot overhang with my timberframe, and in a place where snow is not an issue like Thailand I can see going bigger, especially if you were to brace it back or post it. You could obviously use a conventional frame and use the posts as the porch posts and hang a wall where you want to enclose a living space. Straw-bale timber frames also achieve good overhang by using wrap around porches.

I am going to go out on a limb and guess that "back in the day" when timberframe houses were the norm, utility and function was key. If you were going to build a house, you would maximize it with a second floor and conventional gables are easier to build (IMO). Also, when I think timber frame climate, I think cold, and there a second floor is a warm sleeping bonus, vs the sweat-box it would be in Thailand. And since timber frames tend to mimic earlier styles that is why there aren't many hip roof frames around.

That doesn't mean they can't be done though. What kind of lengths and dimensions of lumber are readily available in Thailand??? I would think you would need some long timbers for the hips...

Dave

witterbound · January 09, 2010, 09:20:52 AM

Most timber frame homes around here don't run the rafters outside of the walls. In other words, the frame is enclosed under the roof and inside the walls. Folks just don't want to expose their timber frame rafter tails to the weather, nor do they want to worry about shrinking timbers and gaps to insulate. In my frame we added brackets to the walls (and also tied them into the roof) to carry the 3 ft eaves. The compound joinery of the hips will complicate your first frame by tenfold. If you know how to layout hips on a stick framed roof that's a good start. Learn to use google sketchup (its free) and you can draw the hips in 3D, which also helps a lot. Start drawing your frame, and it will develop over time.

canopy · January 16, 2010, 03:30:03 AM

Good comments. And witterbound, I especially appreciate your tip about google sketchup. Thank you, it is such a great tool!

My hope was someone has made a hip & valley frame and I could see it and use it as a basis for my needs. Before I give up and use a traditional bent frame with no hip and valley, I thought I would share a sketch showing the problem I have which is a very complex joint at the ends of the ridge beam.

Don't worry about the red tank, it's just a place marker to have appropriate clearance for a passive solar water heater. By the way, the reason for the long eave overhang is I wish to use a leichtlehm (straw-clay) wall system and keep it protected from rain as much as possible.

Jim_Rogers · January 16, 2010, 06:18:43 AM

Drop the ridge beam down and run the afters up and over it.

And then extend the ridge out past the post to have enough to set the end rafter and two hip rafters onto it as well.
This will eliminate any thrust at the plate.

As shown leave a gap between them, so that when the ridge beam shrinks the rafter will then touch. If you make them touch now and the ridge beam shrinks the rafter won't be correctly supported.
Just some ideas.

moonhill · January 16, 2010, 06:28:50 AM

And/or they don't touch at all, even after shrinkage.

Tim

canopy · February 10, 2010, 08:59:01 AM

Dropping the ridge beam does seem like a good idea as it allows for some extra joint space. While I can figure angles, choosing proper joinery is still a question mark. At this point I think it is best to seek an expert. What I need is someone to polish out the frame layout, size the wood, and define the joinery. I am willing to pay for such help. Any ideas where to turn to at this point?