I wish to build timberframe roof trusses to span 22 feet, of which the center 14 feet needs to have as much overhead clearance as practical and cost effective.

Were can I get examples of designs of such a truss? Are there trade off's between roof pitch vs added center clearance?

Is there a source where I can beg/borrow/buy a design for a reasonable price?

BTW, I'd like to use Eastern White Pine. The roof will need to support upstate New York snow loads.

Joel

where is the 2nd floor in relation to the truss?
could the bottom chord be part of the floor?

Mark...

Thank you for your reply.

Actually there need not be a second floor...except for perhaps minimal storage.

The frame will be for my boathouse. Usually, to limit neighbor complaints, height is kept to a minmum. Is is common to use low pitch hip roofs...which personally is not my favorite style.

So...to keep the ridge height reasonably low, I'm thinking about having the wall height lower than it would be for a hip roof, and gain needed "bridge clearance" for the boat by using a raised bottom cord truss. That way, the roof pitch would be steeper without the overall ridge height be nescessarily being any higher.

The trusses/bents would be perpendicular to the boat's centerline. The space under the truss/bents would be 4 foot wide dock, 14 foot wide slip, and another 4 foor wide dock...total span of 22 feet.

Joel

how high are the sidewalls going to be?
I've had a photo of a truss on my pc's desktop for a while that may work....It's from the hamlet heavy timber website:
http://www.heavytimberwork.com/gallery_res_mont.html
If the link doesn't take you right to the truss, then look at the photos of the pye residence...
Check out the photo in the top left corner of that gallery? This truss has curved members, but straight pieces would work also....
You could also consider a hammerbeam, but I think your docks would be crowded as the braces need to start low on the posts.

How many bents are you planning to use?

If you find a design you like, you could copy it and then take it to your favorite engineer for analysis and a stamp if neccessary

Looking through the many timberframe sites on the internet will provide quite a few ideas..

Hi Mark...

The outside walls will be in the range of 8 to 10 feet high, which is plenty of headroom for everything except the center 14 feet (the actual boat slip). I'd like to use about a 12-12 pitch and get a few feet of additional head room by raising the bottom cord.

A hammer beam would work fine if the raised cord can be 14 feet out of a total of 22 foot span.

The boathouse will be 22 feet wide by 44 feet long. I'm thinking of using 5 bents spaced 11 feet apart.

Joel

In drawing a sketch of a hammerbeam into the dimensions you provide, I think the 14 foot center section is too much. However, I'm not an engineer....
It sounds as though you would like the center 14 ft. section to be around 12 feet high?
This is not easy(neither hamlet's frame nor a scissor truss wants to go that high)... could there be posts at the inner edges of the docks?
If this is possible, it would simplify joinery, lighten the timber sizes and raise the 14' center beam to 13 feet(you would, however, need and additional 10 peices of timber for the posts...) you could always stick frame the sidewalls to make up for it???

Mark...

I was concerned that the 14 foot center might be too much for a hammer beam. Anyway around this?

Adding posts to reduce the span would make washing the boat a real pain. I'd like to avoid interior posts.

Joel

Perhaps there is someone with more experience who could make a suggestion??

would braces be ok in the upper corners of the 14 foot clear space? And what is the minimum hieght needed for the boat?

Mark...

Thank you for your continued assistance.

There is no magic number for the height...depends on what boat one owns at the time. I'd guess the cord should be raised a bare minimum of 2 feet...the more the better!

Braces in the upper corners might be a problem. On the plus side: I'd guess the biggest boat likely to be used in a 14 foot slip would have a beam of 12 feet or so. Also, it would not be uncommon for the upper part of a boat to be narrower than it's beam. On the minus side: Boats move, pitch and roll with wind/currents/wakes...

Nothing good oould come from a boat making contact with a timber frame! YEEKS!

Joel

Joel,

Like Mark I am not an engineer but I remember being told that if the bottom chord is kept within the bottom third of the truss it is considered the same structurally as if it is at the truss base. Going on this assumption and based on a 22' inside total span with 12:12 pitch you could move the bottom chord up a max of 3'8". With a 10' sidewall height this would give you a nominal center height of 13'8". The width at this point would be a nominal 14'7". A King Post truss design or rafter/collar tie application would be practical. Please verify the 1/3 rule with a qualified engineer before taking my word as gospel. I could be very wrong.

Thank you for your post.

If you're right, that added 3' + would be great!

I'm going to research this a bit.

Thank you!

Joel