Douglas Fir span question...

[appster99]

First off, thanks in advance for allowing me to be part of this forum.  Knowledge gained here is invaluable for DIY'ers who take pride in their work.  On to the topic at hand...I have a small project which has been approved by the building inspector - almost.  His beam span chart only deals with dimensional lumber and he asked that I consult an engineer at a building supply lumber yard to ensure my proposal is of sufficient strength.  My problem is that everyone I talk to has the same problem as the inspector - no experience with big beams.  The yard I am buying my beams from is a wholesaler and do not have an engineer on staff.  All the inspector wants is a verbal OK, no stamp. 

The project: 21'x21' structure with a 12/12 pitch roof.  I will use common lumber for the roof system just for the ease of working and to make the inspector comfortable.  There will be a loft area on one end measuring 12' deep and the width of the structure.  I want to use rough sawn 8"x8" No. 1 structural grade Douglas Fir from the ground to the top plate.  The loft floor system will be broken into three joist spans of something less that 7', since the total building is only 21', with the end beams having 6" tall pockets cut 2" deep, and the two interior beams having the same size pocket cut on both sides to receive joists.  The joist will be true 2"x6" Douglas Fir as well.  The 21' span will be supported by four posts.  The longest open spans of the entire project are the aforementioned 12'.  So I guess my question is; should 8"x8" not be more than enough strength for this project?  Any and all help is appreciated.

Brian

[giant splinter]

Brian
All your horizontal lumber has a specific maximum allowable span and the span tables are based on the loading of these members, It would help if we could see the plan or somehow get a better idea of what all the bearing loads and snow load if that applies to your project.
You can look up the maximum allowable spans for any size of lumber right from a span table, however to get the correct answer you need to consider your bearing, static, seismic and dynamic loading.
I think we have a set of span tables on the forum but I was unable to locate them.
I will go searching around to see if I can locate the span tables, others should be able to help you with this as well.

[appster99]

I'll have to check with the inspector to see about snow load, but I am in the foothills of NC right at the base of Pilot Mountain where, unfortunately, significant snow has become rare.  The live load will be minimal since the area is just a sleeping loft.  The only beams the inspector questioned were the two beams that have joist attached on both sides.  I have attached my proposed floor plans for the ground level layout and the loft floor system.  "B" and "C" are the beams in question.   What appears to be a beam at the head of the bed is actually a knee wall that the bed will set against with a small access door for storage.  The blue boxes are my post placement.  Does anything immediately jump out as inherently wrong?  None of the interior posts support any roof load, only the exterior walls which are already framed.  The current roof is 5/12 which I am replacing with the aforementioned 12/12 and framing using dimensional lumber.  I am retrofitting an existing building.

Span table question...Tables give span distance for a solid beam.  According to the tables I have found 8"x8" Douglas fir can easily handle the span I am using.  However, what I would like to know is how much strength is lost when the beam pockets are cut to receive the joist?  There would still be 4" wide by 8" tall of solid material for 6" and the full 8" wide for the bottom 2".  Is my reasoning wrong?  I tend to try to use logic, but some things defy me 

Thanks for the feedback!

Brian

[giant splinter]

Brian
You are using what we call "fuzzy logic", is there any way you could use joist hangers or pressure blocking between the joists?.
If you have an open beam ceiling those may not work, how about headroom for letting the joists rest on the beam? Is the ceiling open framing?. Do you have room for your floor joist to run across the top of the beam. If your floor joists are resting in a pocket on an open beam ceiling what are you attaching the joists to the beam with?.
Would you check your dimension for the floor plan I thought it was 22'0"X22'0" However it looks rectangular.

[Jay C. White Cloud]

Hi appster99,

I tried following along a little. I had a few questions.

Are you going to do this as a timber frame?

Do you have any Sketchup files on this building or some isometric drawings you could post?

Regards,

jay

[appster99]

Thanks for the reply's gentlemen.  I had indeed considered just sitting the joist on top of the beam and blocking at the beam.  I have room to do it.  My only reason for the pockets for the joist was to pick up a few inches of head room, which I don't really need, and to practice my chisel technique.  It was more for the experience than anything.

The room is indeed rectangular on the floor plan.  The laundry area, bathroom, and closet space will be under a 10' lean-to shed roof which will be framed the easy way - conventional lumber.  I have a lot of experience with framing using 2x material, but not timber framing.  The cabin I'm trying to build now was supposed to be a practice project.  I will eventually build a larger timber frame home, but the little cabin will suit my wife and I until we have children...if we ever have children!

Jay, the only files I have are the two attached and one other, which I have attached to this reply.  These are the drawings I took to the building inspector for my permit.  A brief back story, we bought land which used to have double wide trailer on it and a free standing 2 car garage.  When the lady passed away the bank repossessed the home and we bought the land from the estate.  We are trying to turn the two car garage into a cabin by adding on a 10' lean-to for the laundry and bath room.  My wife and I love barns so we wanted to make it look like a barn.  We also love the big beam look of timber framing so I am retrofit the garage with beams on the inside.  Right now the building is walls and a roof on a slab.  The roof is currently a 5/12 pitch so it doesn't allow much room for a loft sleeping area, so I'm changing that to 12/12.  The living area will be under the loft and the kitchen will be along the adjacent and opposite wall.  I wanted to try my hand at building the loft with beams.  There are other posts on the drawing but none of it will actually provide any support to the roof system.  It is mainly for the look.  I plan on building other buildings on my farm from scratch using traditional timber frame techniques and materials, but this project was just to get my feet wet.  All that being said, please destroy my drawings so I can learn.  I would love to know any and everything I did wrong with my drawings.  I genuinely appreciate criticism as a mode of learning.

Brian

[Jay C. White Cloud]

Hey Brian,

Welcome to the FF, sorry I didn't say that before.  You came to a good place, folk here will love to help. You draw pretty good, have you ever tried to use Sketchup?

[appster99]

Thanks for the compliment.  I enjoy drawing and putting to paper what the voices in my head are screaming.  Just Kidding!   I'm not familiar with Sketchup.  Is it one of those free online things or a package for purchase?  I'm always up for learning something new.  I try to learn something significant everyday.  I'll Google it and see what I can find.  I have a feeling once I start playing I'll be up all night trying to master it!

If I can go back to the reason for my original post - What size posts and beams would you recommend given the spans and my design?  Are there simplifications or changes to my design that you see are critical.  I'm trying to meld two styles of building since I have existing conventional framing that I want to look like timber framing.  If I can go smaller than 8"x8" I'm open to that.  I can get virtually any size in Douglas Fir, but I don't want to go larger than needed because I'm building in place and lifting either by hand or with a jack or with forks on a Bobcat.  Since the exterior walls are already in place it is difficult to assemble the entire bent and raise it.  (I hope I'm using the terminology correctly.)  I just love trying to build anything - especially when it involves an honored skill that few people are brave enough to try.  Thanks again for the advice!

Brian

[Jay C. White Cloud]

Hi Brian,

I'm really busy currently, so I'm only half with you on your plan.  I was hoping some other folks will jump in too.  If I hand it a CAD program, (like Sketchup) I could "digest" it a bit faster.  Give me some time and I will get more of your plan in my head. 

You will be surprised if you try Sketchup.  It is a Pro level program with a world following.  There is a Pro version for about $500 but that only adds some blue print option and other Architect level stuff that we would use.  For the average client the free version is more than enough to make drawings and open files for other users, like here on the FF.

My general feeling, from what I have gleaned so far from your verbal description, is the project is doable in an all timber frame format.  Maybe even bent style, if you don't mind having the old roof off for a few hours/days.

Will you be buying the timbers from a local sawyer?

What area are you in?

What species?

Do you have a time line?

Regards,

jay

[appster99]

Jay,

My lumber will come from Boone Lumber in Lenoir, NC.  They are a small wholesale company with Western Red Cedar and Douglas Fir material in many different sizes.  Their website is www.boonelumber.com. Its about 85 miles from where I live, but the prices are 30% less than anything I have found closer to my location.  My cost to drive and pick it up is much less than the price increase and delivery fee for local companies.  The species I have chosen is No. 1 Strutural grade Douglas Fir.  I can get it rough sawn, S4S, or another finish where they send it through a band saw, which is most expensive.  I forget what that finish is called.  The salesman said all beams are partially air dried and have 15-20% moisture content.  My understanding is that as long as all material has close to the same moisture content and everything dries together I'll not have problems with different shrinking rates.  Is that accurate?

My time line is an odd thing to pin down.  I'm in no real hurry to finish, but am anxious and excited to get started.  I guess the best answer is "as soon as is feasible."  I should have my building permit next week.  Once I get the permit the mason will do the foundation for the lean-to addition and I will frame the floor system and decking, then the walls.  I work 60-65 hours a week on average at my paying job, but typcally have two days off - Sunday and Monday.  All my cabin work will be on those off days.  I'm no stranger to 16+ hour days and will work from sun-up until I am too tired to continue, but there is only so much I can get done in only 30 or so hours packed into two days a week.  By the time the addition is framed I'll need to have provided the inspector with "proof" that the proper size beams are to be used.  He is very easy to work with and only wants me to have a verbal approval from an engineer who agrees my beam choice is sufficient.  Hense my joining this forum to learn so I can take something reasonable to an engineer and not get laughed at.  I really do sincerely appreciate all your help thus far and thanks in advance for any other advice you share.  I'm going to check out Sketchup and hopefully that will help me provide better information to you and make it easier for you to help me.

Thanks Again!
Brian

[Jay C. White Cloud]

Morn'n Brian,

I'm sure others will start "wading in" once they see more graphic work to consider.  Something I would strongly suggest is trying to support a local sawyer.  There are many all across the country and will provide you the timbers you need.  I know of Boon Lumber and have nothing against them, but I don't care for wood ship across the country to an area that has all the wood it needs and the folks to mill it.  As a traditional timber wright, green wood is what I work in, not only for our frames but many other projects as well.  The fact they are going to charge more for the wood with a "saw kerf" finish is rather strange?  You normally pay more to get rid of saw marks, but I believe you because these are probably timbers that have already bean sanded or planed.

I'm sure a local fellow in you area probably wont charge more than $0.80 per board foot or lower.  The one challenge you may face, depending on the county your in, is have the lumber graded.  We don't have that requirement up here or in many areas we frame, but, for what ever reason, North Carolina has it in some areas.  I do know there is a Senator, that is apparently a miller, that is trying to change that for the "owner builder."  Ask your the folks you got your building permit from, they may even know of a locale sawyer.

Anyhow, let us know about finding your wood local.  You may post another thread requesting help with that.  One of my students lives in Asheville and owns a tree company (Smart Fellers) and still timber frames on the side.  How far are you from Asheville? I know he has several custom millers he works with for his frames.

Regards,

jay

[appster99]

There is a local guy whom I bought 1x8 poplar from for siding.  His brother does the logging and he has a mill.  I'm pretty sure I can get oak from him but he primarily deals with Poplar since that is what is on his land.  As you alluded, I'm pretty sure the inspector will require the lumber to be graded.  Boone Lumber was by far the least expensive place I found to get graded lumber, but you are right, their wood comes from Canada.  I'm 3 hours from Asheville, but will gladly make that trip if the price is right.  In my business I buy from local farmers for ingredients in my restaurant and support local businesses by referring them as much as possible.  However, sometimes the budget is difference.  If you can pass me the information of your contact I'm more than willing to try and throw him my business.  If not him, maybe he knows someone closer to me.

I downloaded and played with Sketchup for a couple hours last night.  I think this is going to be my new addiction!  Thanks for the insight for that program.  I had never heard of it before, but it gives me a great medium to express my ideas.

Thanks!

Brian

[appster99]

Alrighty then Jay!  Since last week I have been playing on SketchUp and have a decent handle on it - especially since I work 65 hours on the paying job and just did my drawing in my spare time.  I have tweaked the design to eliminate the two beams the inspector questioned.  I know there are still a few things that aren't perfect but I think this is a good start to give you and idea what I'm working with.  The base 22x22 floor is the current slab.  The shed roof addition does not exist at all at this point.  The raised section rising from the floor is 8" block rising 12".  On top of that is a 2x4 wall I will fir out to 6" to meet code for insulation.  All posts will be inside that on the concrete - with a plate for them to sit on of course so they aren't directly on the concrete soaking up moisture.  I have found a local guy, 15 miles away, who can saw 8"x8"x12' Yellow Pine for about $6 per timber.  That's down from about $100 per Douglas Fir for the same dimensions.  Thanks for making me do more research - I cut my lumber bill by 94%!  I drew the joints that sit on the posts as simple lap joints with 2" of the top part of the lap still resting on the beam for support.  I am open to recommendations on how to tie the beams back in.  I'm curious to hear your thoughts.  Don't make too much fun of my drawing, I never even heardof SketchUp before a week ago.

Thanks!

Brian

[Jay C. White Cloud]

 8)

GREAT JOB!!!!!

Now I have something to stick my teeth into.  I am really busy at the moment but have created a Project File on my desktop for you (as I do for each FF member that requests assistance,) and I have reviewed your draft drawing.  I wouldn't laugh at all at it.  I am actually really impressed with how much you have achieved in such a short time.  We will "iron out," the details in short order I am sure.

Till later,

jay