Chosing joinery for the design?

Hi,

A man that own big beach house with enormous deck wants me to build him a Timber Frame rooftop for his deck. He wants it to be 16' X 18' and that would cover maybe 40% of his deck. His deck is roughly 4 feet above the ground. He have many 5" X 10" X 14' yellow pine he wants to use. One thing that must be considered is high wind because his home is sitting on the sound, and other thing to consider is salt in moist air that could deteriorate his pine lumbers over the year that safety might become an issue??

While I am a bit reserved about designing him a plan because I am no engineer, here is some idea I was thinking of before adding braces.. Not sure if this will work? I am more concerned about the engineering safety for this. I wish I knew how to calculate few formula to determine if this is a good method and what joinery to use for this? The owner seems keen on trying to keep his cost down I am afraid I might can't take his project because I don't want to be liable for it.

See pic here .

I have not get to ridge & purlin, and braces are missing. I was thinking of using 5X10 post with 10 being inside to support the 5" side beam at top. The tie beam supporting King Post, I suggested going with hardwood (oak) so it will not sag over the time that you will expect from pine and owner was willing to go with that. Another uncertain is footing for posts. I was thinking of maybe a pressured treat 8x8 pine or hardwood 8x8 and cut mortise hole on top of it then put rest of body down underground with few rebar crossed, fill it up with cement then put post on top of it with bottom tenon going into mortise hole, steel bolt through it. I haven't done any drawing on it but I can if you want better picture of what I am trying to say.

To my surprise, building inspector said that no permit will be needed (???) so I would consider hiring a designer with more knowledge to help me draw up a plan.. But if you are happy to give me some pointer, that would be great so I can learn in the process for my benefit. Thank in advance for replying and helping.

You would probably be well off on using an engineer, for everyone's peace of mind. The right engineer who knows his timbers will also be able to give you feedback on joinery choices as well. If the customer does not want to pay that is his loss. It sounds like he can probably afford it. It is absolutely not worth putting yourself out on a limb on. If you are uncomfortable, don't be afraid to say no. Good luck with it!

You must protect yourself...!!!...a PE is a must for such a job!

Feel free to contact me to discuss or call Fire Tower PE...I have worked with Ben for over 30 years!

This type of job requires at least a "check in" on your design by someone like Ben!

Good Luck,

j

and You must protect your customer! More often our job is to save them from themselves anyway isn't it?

I can vouch for Fire Tower as well AND strongly recommend an engineer for this type of structure.

I agree with the sentiments above. Its in the best interests of the structure and everyone involved.

Most of my work is open air in Exposure C. I'm on the coast. So I can at least add a few thoughts if to do nothing less than save you engineering hours.


1. Timber Species: There is a goldmine of quality Cypress timbers just southwest of you procured from the Cape Fear River Basin. Would be my choice.

2. Timber X-sections: I know that you had 5X designed because of material at hand. Looks too weak to me, very bendy. Would be hard to have opposing knee braces on center post as well.

3. Wind and Uplift: Think 7/8 stainless all thread with timberlinx at post bottom, post top thru plate thru principal rafter, and apex (level). Timber braces in wall plane, bent plane, plumb ridge plane to king, and possibly bracing in the plane of the roof depending on strength of roof diaphragm.

The connections above are only as strong as the connections below when dealing with kites. The existing deck can probably be examined for a good connection with some ingenuity and additional structure. Keep in mind that a pegged connection will typically not meet requirements for 130mph winds. Not to say you cant use them (for instance at post top), but imagine a threaded rod going through the tenon as well (plumb) with nut and washer above.

Also think of the handrail height and how it might benefit.

Anyway, hope this helps. Pretty close to you if I can be of assistance.