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#33970 - 09/15/16 09:10 PM Floor Dead and Live Loads for Small TF
EPops Offline
Member

Registered: 09/14/16
Posts: 3
Loc: Buffalo, NY
Hello all, this is my first post here on the forums. I have a timber frame (TF) workshop designed (for working timbers in inclement weather). I have a question on loading for floor systems. And possibly suggestions on sizing/spacing on floor joists.

First, my TF is 16'8" x 24'8" (including size of the 8x8 sill plates). Made of Eastern Hemlock. I am considering 4x6 floor joists.

My question is: what should be considered for dead and live loads on a flooring system? I am a civil engineering grad student, and know about the loading values stated in code books. But for a small workshop TF, I cannot find much reliable info. And I have no experience in analyzing timber structures.

I have seen as high as 12 psf for dead loads and 40 psf for live loads for a flooring system. I highly doubt that my structure will see values as high as those. The live load will consist of:
1.) Maximum of three people (600 lbs)
2.) Maximum of two timbers at a time, with sawhorses (600-700 lbs)
3.) Two or three workbenches - unsure of weight
4.) Wood stove
5.) Tools (mostly hand, very limited power tools - and none larger than circular saws or chain mortiser)
6.) Tool storage

With a very conservative estimate of 2500 lbs total live load, across a 16x24 (384 sq. ft.), I am looking at 6.5 psf live load. With a deflection limit L/360, that would be about .39".

And for the dead load, I assume that only the floor joists and floor boards would actually contribute, since the sill plates are resting on concrete piers. Would the sill plates come into the value of dead load? And would 1" flooring be adequate, or should a sub-floor also be used?

So I have seen in one of Sobon's books, 5x7 joists with max spacing of 2' 6". Assuming he is using the code standards of Dead=12 psf and Live = 40 psf.

Can 4x6 joists be spaced maximum of 2' 9" O.C. while spanning nearly 12', in my case described above? Or does this sound bad? Spacing varies in my design (non-uniform), with min=2' 8" and max=2' 9". I would need dead load to get load combos in LRFD, to get my actual deflection.

The joists are tapered to 4" to avoid shear failure. And the center joist in each bay is dovetailed.

Any suggestion for alternate joist sizing/spacing/span would be appreciated.

Thanks a bunch if you followed me all the way through this post. I, along with my brother (who is also an engineer and worked as a timber framer for a year), are hoping to get more involved with TF and help bring this great style of building back into the mainstream. I appreciate your help and look forward to getting to know people on here.

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#33971 - 09/16/16 07:03 PM Re: Floor Dead and Live Loads for Small TF [Re: EPops]
TIMBEAL Offline
Member

Registered: 12/10/07
Posts: 1873
Loc: Maine
Welcome aboard Epops. I would be concerned with a bouncy floor if things are under sized. One guy chopping or pounding away and the other trying to hold the square in an lousy position, the bouncy floor will only add to the already lousy position. As a student of such matters we know the loads we choose for the direct use of the structure can and does change in a few years. A heavier system will ensure that change in the future will be met. I would not have any issues pushing those 4x6 out to 4x7 or even the 5x7. Also consider the center dove tail to be exchange for a tusk or soffit tenon and tenon it into the face of the center beam, this will keep the top cord of that beam in tack. What size tractor will you park in there? Got some spare engines that also need cover lets put them in the shed.

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#33973 - 09/16/16 11:19 PM Re: Floor Dead and Live Loads for Small TF [Re: EPops]
EPops Offline
Member

Registered: 09/14/16
Posts: 3
Loc: Buffalo, NY
Thanks for your reply, there won't be any tractor or other heavy equipment, just a few guys with a couple timbers. That is why I thought the design loads in code books are too high for this structure.

I was already thinking of decreasing the spacing between the joists, but have been hoping to save money while also keeping it safe. I will try out a few more calculations for deflection with those other members, and look into the other types of joints.

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#33974 - 09/16/16 11:32 PM Re: Floor Dead and Live Loads for Small TF [Re: EPops]
Jay White Cloud Offline
Member

Registered: 11/06/08
Posts: 479
Loc: Vermont
Hi EPops,

I second everything Tim suggested, and probably would take the joists up to 6x8 or place closer. In most frames I've experienced like this they are seldom further apart than 24".

I would add, that PE and Timberwrights alike don't just design a structure (as long lived as timber frames often are) for only one intended purpose. You personally may not need a combined load capacity as high as some would suggest...Nevertheless, what is reflected in Tim's humorous (but very accurate) "tractor" or "engine" storage comment at the end of his post has much weight and wisdom...This frame could have all manner of intent placed on it (as such structures often do in the course of time) and its our job to think of this in our design and building of them.

Just some food for thought...
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http://about.me/tosatomo

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#33975 - 09/17/16 06:36 AM Re: Floor Dead and Live Loads for Small TF [Re: EPops]
TIMBEAL Offline
Member

Registered: 12/10/07
Posts: 1873
Loc: Maine
The tractor and engines were on the lighter side. But I would reinstate the aspect of a springy floor and layout, bouncy work is irritating. I would also suggest the thought of a concrete floor for a work shop setting. I do see the benefits of a wooden floor though. Then flipping again I could not give up my concrete floor for my shop. It makes a great lay out lofting place for those time scribe work comes into play. But now we are venturing in redesigning the building which I don't think is appropriate for this topic.

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#33977 - 09/17/16 12:44 PM Re: Floor Dead and Live Loads for Small TF [Re: TIMBEAL]
Jay White Cloud Offline
Member

Registered: 11/06/08
Posts: 479
Loc: Vermont
I do agree entirely that the floor joist as presented (and for this frame as described) does seem that it could be possibly a bit too springy to me as well. Too much spring is as bad as too hard/stiff a surface to work on...

We will have to disagree on the concrete flooring Tim. I have too many friends and collegues with severe to chronic lower back and leg issues from standing and working on concrete floors...

Beside the environmental impact the entire industry has on the environment, and the less than questionable durability of modern concretes (e.g. our steel and concrete infrastructure is falling apart)...there is clear evidence of the health risks associated with standing and working on concrete. Yes one can lay matting down as many factories now do (and some areas require by law) yet just using wood solves the issue nicely, and fits a timber frame much better (in my view aesthetically.) I have seen great Lofting Floors in wood as well so that isn't really a challenge to not using wood. Even a stone paver system laid in sand is more giving than concrete is, and these too have been employed for lofting when installed neatly and for that intent.

Just a sampling of info about concrete floors...There is a great deal more out there:

Redfern and Chaffin (1995)
"...Flooring did affect workers perception of discomfort and all floor surfaces were rated better than concrete...."

Krumwiede et al., (1998)
"...investigated the effects of floor surfaces on comfort ratings in 3h of prolonged standing with 1h on each type of floor surface. Mat compressibility (ranged from 2.2 to 8.9%) was important in the comfort ratings and all surface types rated better than concrete..."

Originally Posted By: Hazards.org
Flooring
Hard, concrete floors are about the worst possible surface. Materials that provide flexibility such as wood, cork, carpeting, or rubber are gentler on workers’ feet. Concrete or metal floors can be covered with mats...
...Avoid standing on concrete or metal floors. Recommended for standing work are wooden, cork or rubber covered floors. Ensure that the floors are level and non-slippery. Cover concrete or metal floors with mats. Slanted edges on mats help prevent tripping..




Edited by Jay White Cloud (09/17/16 12:48 PM)
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#33978 - 09/17/16 01:33 PM Re: Floor Dead and Live Loads for Small TF [Re: EPops]
TIMBEAL Offline
Member

Registered: 12/10/07
Posts: 1873
Loc: Maine
To clarify, my shop floor is also my milling operation, which sees much heavy use from my small 9 ton excavator to 40 foot logs skidded across it to joinery and truck repair, as well as lofting. I do appreciate a wooden floor, though.

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#33979 - 09/17/16 02:18 PM Re: Floor Dead and Live Loads for Small TF [Re: EPops]
Jay White Cloud Offline
Member

Registered: 11/06/08
Posts: 479
Loc: Vermont
I apologize if my other post sounded like you should undo what is working for you...By all means keep it if it works, and you're happy with it...

Additionally just food for thought Tim, and our other readers...

I have been in a number of operation over the years that have massive floor load requirements and then some, such as storing a tractor collection, Sawyer operations and other Mass Related storage needs. This can be found both on first, second and third floors of old bank style barns and vintage Factory, Mill and Dock Warehouses.

This isn't to negate your shop, but just to suggest that perhaps anyone designing and/or having what you do, could improve the work area (and its comfort/safety) by adding matting...even Wood Matting...to such a system where primary walking/working is done. We have placed wooden floors over entire concrete floors just for this purpose and reason to good effect. Even now we avoid concrete whenever possible by employing vintage approaches to to foundational systems and using gravel for first floor systems. Instead of concrete slabs, a floating wooden floor is installed over sleepers on the gravel.

Just an alternative suggested system to concrete...

Regards,

j
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http://about.me/tosatomo

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#33980 - 09/17/16 06:04 PM Re: Floor Dead and Live Loads for Small TF [Re: EPops]
TIMBEAL Offline
Member

Registered: 12/10/07
Posts: 1873
Loc: Maine
I have thought about doing some of those things. Very worthy of consideration.

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#33981 - 09/17/16 06:51 PM Re: Floor Dead and Live Loads for Small TF [Re: EPops]
Jay White Cloud Offline
Member

Registered: 11/06/08
Posts: 479
Loc: Vermont
I don't think you would regret this augmentation to your current system at all Tim, and with your tool and skill sets, it should be a relatively easy addendum to the concrete floor system you have now...

I haven't had (or seen) a complaint of noteworthiness yet from anyone switching from concrete to wood, nor those that upgraded to their current slab system with wood...

Those of us with the luxury (and/or skill sets) to install wood floors (floating or fixed) thus far have all been rewarded with less Back and leg pain for our efforts. I would also note, that it is a great way to take an old, cracked or uneven concrete slab and more cost effectively improving it without removal of the original materials...I have seen or done this to Basements, Garages, and many other structures with slab floors. Where gravel is in place on contemporary systems, the use of wood over gravel (in my view) is a vast improvement both ergonomically and environmentally, to ever employing concrete.

For radiant heat systems, a simple layer of geocloth over the gravel layer, then sand or stone dust to hold the tube labyrinth is more than enough to facilitate all manner of tile, stone or related Hard Surface flooring material...even wood...Yet, because of the sand/dust embedment material still offers much greater cushioning than a monolithic slab system. It is usually much more cost effective as well (big picture) in the long run, and facilitate repairs/upgrades better than any monolithic system.

Regards,

j


Edited by Jay White Cloud (09/17/16 07:01 PM)
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