Timber Framers Guild

Is my rabbit hutch structurally sound?

Posted By: AJGibson

Is my rabbit hutch structurally sound? - 10/29/15 06:50 AM

So, this is my first timber-frame project: a rabbit hutch for my mother:

(Some sides cut away to give a view of the joinery)

A single long cage will rest on steel rebars fitted into the holes in the lower beams; the "2nd floor" is for storage (feed, hay, blankets for winter, etc.)

Most of the mortises and tenons have already been cut, but a few (such as the knee braces (right term?)) have not, so there's SOME room for change, but not much.

I should have put this all into SketchUp and asked for advice here from the start. But better later than never, I guess.

Anyways -- is this sound? Are my tenons long enough? Will it collapse in a heap and kill my mother's poor rabbits?

The posts, and main beams, are 4x4s, the span is 10' by about 3', it's around 9' tall. The tenons are all 1 1/2", with a 3/4" shoulder/housing. The "joists" on the "2nd floor" advance 1 3/16" into the beams and have a depth of 3/4"; the "floor planks" are 1 1/2" thick and are simply laid on-top with interlocking edges.

Where should I place pegs? How big should they be?

(I'm unsure of all the terminology...bear with me...)

It's been a steep learning curve (the rafters were a *&#!^), and I've been mostly teaching myself, but the process has been extremely enjoyable. Hopefully this thing can actually work, too. I've been bitten by the timber-frame bug and there's no going back; please help this newb find his way down the path smile
Posted By: AJGibson

Re: Is my rabbit hutch structurally sound? - 10/29/15 08:00 AM

Googling around, I'm finding rules of thumb that say a tenon's length should be 5x its thickness, and the thickness should be 1/3 the width of the piece it's going into. But for joining two 4x4s (3 1/2" x 3 1/2"), the thickness is 1 3/16", and 5 times that is...well, *a lot*: basically 6 inches. That's straight through the 4x4, that doesn't make sense. But my tenons are really short. Is this going to be a problem? How is this supposed to work?
Posted By: Jay White Cloud

Re: Is my rabbit hutch structurally sound? - 10/29/15 01:12 PM

Hi AJ,

I have been following along on both your post, and I'm glad you have headed Timber Wrestlers guidance of tackling something less challenging as your first timber frame project besides a roof structure which can be very daunting for anyone.

As this is a "timber frame forum" I won't bore our readers with "animal enclosure designs" but there are many issues with the hutch that are well beyond timber framing challenges. So on that note, I would offer that you can freely email me anytime to discuss the needs of Leporids and other small rodent species enclosure requirements/systems.

My last suggestion is that learning timber framing from just books, conversations (and worse...what is just on the internet) may be frustrating for some students...If not just a bad idea in general. Timber framers, as a generic group of folks, love to talk and look at publications (including forums) about this wonderful craft. Unfortunately most of our kind are also kinesthetic (aka hands on) learners and fail miserably at actually internalizing what is need to be known from verbal (written or speech) information alone. As such, I would strongly recommending finding a local Timberwright and introducing yourself, while also joining the TFG and attending the programs/conferences it has to offer...This is going to be the best way perhaps to get all your questions efficiently and thoroughly answered...


Posted By: Jim Rogers

Re: Is my rabbit hutch structurally sound? - 10/29/15 01:58 PM

Tenon lengths can vary depending on the needs of the frame. Normally some standard rules are that the tenon thickness is 1/4 the timber width.
For example an 8" timber has a 2" thick tenon and it is usually offset from the reference face the same distance. Making it a 2" offset.
So, for a 6x6 it would be 1 1/2" tenon and its mortise and offset 1 1/2" as well.
Now for peg sizes it is usually 1/2 the tenon thickness. So for a two inch tenon you'd use a 1" peg. And for a 1 1/2" tenon a 3/4" peg.
I make my brace tenons 3" long, usually.

Good luck with your project.

Jim Rogers
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