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EngineerJet

Looking to add flooring to attic for storage. Any structural engineers/architects here?

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That being said I think AVB has this covered. 

I got my own problems . Just got done using roundup on the mulch beds to kill the emerging weeds and when done my wife’s asks me if I noticed her tulips starting coming out.....   they looked like weeds to me and I just remained silent. 

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1 hour ago, Ray Ray said:

I still say 1/4 inch will do.

@Ray Ray:

 You Sir, are now just being a provocatuer, (a.k.a. a wise ass.....) ;)

AVB-AMG

1 hour ago, remixer said:

That being said I think AVB has this covered. 

I got my own problems . Just got done using roundup on the mulch beds to kill the emerging weeds and when done my wife’s asks me if I noticed her tulips starting coming out.....   they looked like weeds to me and I just remained silent. 

Damn......  If I did that, I would not bother coming inside for dinner....  and just sleep in the car....

P.S. - Thanks.....

AVB-AMG

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41 minutes ago, AVB-AMG said:

@Ray Ray:

 You Sir, are now just being a provocatuer, (a.k.a. a wise ass.....) ;)

Speaking from experience.  I have climbed into enough attics, crawl spaces, closets, basements, ventilation shafts, voids or wherever else I needed to get a wire through I can safely say 1/4 plywood will suffice.  

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30 minutes ago, Handyman said:

Sounds like you, only on politics. 

I've seen what you fancy pants engineer type eggheads can accomplish:

Image result for tacoma narrows gif

 

Galloping Gertie! The Tacoma Narrows. A  textbook example of divergent oscillations.

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10 hours ago, Ray Ray said:

Speaking from experience.  I have climbed into enough attics, crawl spaces, closets, basements, ventilation shafts, voids or wherever else I needed to get a wire through I can safely say 1/4 plywood will suffice.  

I was wondering why you spent so much time in those places....  Happy you covered it with wiring :)

10 hours ago, Handyman said:

Sounds like you, only on politics. 

I've seen what you fancy pants engineer type eggheads can accomplish:

Image result for tacoma narrows gif

 

oh it happens from time to time..  there is a building in NYC (Citicorp) that was in danger of toppling over if wind conditions were just right. Repairs were done in the middle of the night to stiffen the joints. No one had a clue until may years later. Funny thing was the issue was found by an engineering student.

It was a major issue and NYC was in decon one weeks before a hurricane was going to hit NYC

link to the story

http://www.slate.com/blogs/the_eye/2014/04/17/the_citicorp_tower_design_flaw_that_could_have_wiped_out_the_skyscraper.html

9 hours ago, Zeke said:

Galloping Gertie! The Tacoma Narrows. A  textbook example of divergent oscillations.

It does make for great footage

9 hours ago, Handyman said:

That thing is rocking more than AVB and the missus after a bottle of port on a Friday night.

I was tired just watching it.

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14 hours ago, AVB-AMG said:

That is a very sensible option.  If the O.P. is going to go to the trouble of augmenting the existing 2x6 wood joists in the attic, I agree that instead of using 2x4 members, to use 2x6 lumber, and then stagger them in section by two inches (2") which would add both stiffness and load bearing capacity to the joists.  When I have done this in the past I recommend using  3/8" x 2 1/2" stainless steel hex head screws staggered at 16 O.C. to gain the desired stiffness and bearing properties. 

This is my current attic plan for the 2x4 riser. The brown lines are the joists, the black line is a wall that runs through the house and the blue lines are the proposed riser. Its not to scale and the number of joists are not exact, just a rough sketch. You had mentioned staggering them in section by two inches. How so?

House Sketch.png

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@EngineerJet:

Ok, if I understand you correctly, what you have sketched above is a plan layout of the existing 2x6 attic joists, rendered in brown colored lines, that span perpendicularly from the exterior/perimeter house bearing walls to the load bearing interior wall.  In an earlier post, you mentioned that the total horizontal length from the two perimeter walls is 20 ft. 6in.  If that is the case then the actual clear span of the existing 2x6 attic joists from each perimeter wall to the central load bearing interior wall is 10 ft. 3 in.  That is at the maximum recommended span for that size wood joist to serve their original purpose. 

Again, if I understand you correctly, your proposed 2x4 risers, rendered in blue colored lines, are just placed on top of the existing 2x6 attic joists, running perpendicular to them.  By doing that, you are not increasing the stiffness or load bearing capacity of the existing attic joists.  All that does is add additional weight (load) on the existing 2x6’s.  Then you would lay your plywood floor sheathing on top of the 2x4 risers.  I would not recommend that you do this layout, as you propose….

Let me explain in more basic terms to try to avoid confusion.  To ensure that you can safely create an attic space for storage purposes, one sensible option would be what @Malsua had originally suggested and I further elaborated on.  That is to augment the existing 2x6 wood attic joists by fastening, (sistering), another 2x6 wood joist to each existing joists, running in the same direction.  When you do this you would offset them in the vertical cross-section by two inches (2”), as illustrated in my basic sketch attached here as a pdf file.  You would need to connect the two attic joists with a secure fastener that would be strong enough to ensure that the two “ganged” 2x6’s are now working in tandem structurally to create a stronger load bearing horizontal member (joist).  That is accomplished by using 3/8" x 2 1/2" stainless steel hex head screws that are installed in a staggered configuration at 16 on center (O.C.) to gain the desired stiffness and bearing properties that will allow you, as well as any future owner of your house, to store whatever you want within reason, up in your attic space.   This approach also will allow for the option to install added insulation between the augmented wood attic joists to achieve a much higher (better) insulating R-Value.

I hope this clarifies what I am suggesting you consider doing.  But as I had recommended earlier, the best route to take is to have either a licensed Architect or a Structural Engineer to come to your home to see for themselves and to verify exactly what your existing conditions are and to then perform the necessary calculations to determine what your various options are.  That would not be too expensive and worth the gained peace of mind that whatever you ultimately decide to do will be adequate, as well as safe for your needs.

AVB-AMG

Section Sketch of two 2x6 joists sistered together.pdf

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4 hours ago, remixer said:

oh it happens from time to time..  there is a building in NYC (Citicorp) that was in danger of toppling over if wind conditions were just right. Repairs were done in the middle of the night to stiffen the joints. No one had a clue until may years later. Funny thing was the issue was found by an engineering student.

It was a major issue and NYC was in decon one weeks before a hurricane was going to hit NYC

link to the story

http://www.slate.com/blogs/the_eye/2014/04/17/the_citicorp_tower_design_flaw_that_could_have_wiped_out_the_skyscraper.html

@remixer:

I was studying architecture in Manhattan back in the mid-1970's, as part of my junior year "abroad" and remember watching the erection of the structural steel trusses for the Citicorp Center building on East 53rd St and Lexington Ave., since my apartment was just two blocks to the north.  It was really fascinating to see such a large building with the columns at its base, offset from the four corners.  The issue was that the steel members, ("V" trusses), were connected using bolts, instead of being welded, as a cost-savings decision.  The link you provided for the story about the structural deficiency for CitiCorp Center was just a cursory overview of what happened, leaving out some important details.  For those of you who may be interested, (you?), here is a link to a more thorough explanation of the problem and the executed solution.

AVB-AMG

 http://www.engineersjournal.ie/2015/12/08/citicorp-centre-tower-failure-averted/

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20 minutes ago, AVB-AMG said:

@EngineerJet:

Ok, if I understand you correctly, what you have sketched above is a plan layout of the existing 2x6 attic joists, rendered in brown colored lines, that span perpendicularly from the exterior/perimeter house bearing walls to the load bearing interior wall.  In an earlier post, you mentioned that the total horizontal length from the two perimeter walls is 20 ft. 6in.  If that is the case then the actual clear span of the existing 2x6 attic joists from each perimeter wall to the central load bearing interior wall is 10 ft. 3 in.  That is a reasonable span for that size wood joists to serve their original purpose. 

Again, if I understand you correctly, your proposed 2x4 risers, rendered in blue colored lines, are just placed on top of the existing 2x6 attic joists, running perpendicular to them.  By doing that, you are not increasing the stiffness or load bearing capacity of the existing attic joists.  All that does is add additional weight (load) on the existing 2x6’s.  Then you would lay your plywood floor sheathing on top of the 2x4 risers.  I would not recommend you do this layout, as you propose….

Let me explain in more basic terms to try to avoid confusion.  To ensure that you can safely create an attic space for storage purposes, one sensible option would be what @Malsua had originally suggested and I further elaborated on.  That is to augment the existing 2x6 wood attic joists by fastening, (sister), another 2x6 wood joist to each existing joists, running in the same direction.  When you do this you would offset them in the vertical cross-section by two inches (2”), as illustrated in my basic sketch attached here as a pdf file.  You would need to connect the two attic joists with a secure fastener that would be strong enough to ensure that the two “ganged” 2x6’s are now working in tandem structurally to create a stronger load bearing horizontal member (joist).  That is accomplished by using 3/8" x 2 1/2" stainless steel hex head screws that are installed in a staggered configuration at 16 on center (O.C.) to gain the desired stiffness and bearing properties that will allow you, as well as any future owner of your house, to store whatever you want within reason, up in your attic space. 

I hope this clarifies what I am suggesting you consider doing.  But as I had recommended earlier, the best route to take is to have either a licensed Architect or a Structural Engineer to come to your home to see for themselves and to verify exactly what your existing conditions are and to then perform the necessary calculations to determine what your various options are.  That would not be too expensive and worth the gained peace of mind that whatever you ultimately decide to do will be adequate, as well as safe for your needs.

AVB-AMG

Section Sketch of two 2x6 joists sistered together.pdf 84.39 kB · 2 downloads

Appreciate the suggestion. Would the sistering joist need to run the entire span of the existing 20.6 feet? Or am I using smaller sections to sister on the existing joist? If I'm using smaller sections, how long should each section be and where along the existing joist should they be placed?? One section in the middle? two sections at every third? Itll be a huge hassle if i have to get another 20' member into the attic, lol.

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10 minutes ago, EngineerJet said:

Appreciate the suggestion. Would the sistering joist need to run the entire span of the existing 20.6 feet? Or am I using smaller sections to sister on the existing joist? If I'm using smaller sections, how long should each section be? One section in the middle? two sections at every third? Itll be a huge hassle if i have to get another 20' member into the attic, lol.

From what you have said earlier, the interior wood wall is a load bearing wall so the new, additional 2x6 wood joists would only have to be 10 ft. 3 in. in length and rest at either end on the vertical bearing walls by at least 2" for sufficient load transferring support.  But you would need to sister the new joists on both sides of the interior bearing wall, to each perimeter wall.   I assume that each of the existing attic joists are that length (10 ft. 3 in.).... Or are they all 20 ft. 6 in long?

AVB-AMG

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22 minutes ago, remixer said:

Dam. That’s about 400per hour engineer work :)

btw can’t open it 

Hmmmm..   Would a friendly FFL possibly give me any sort of $$ credit at their retail store...???
BTW, the attachment to my post is a PDF file.  You will need to have Adobe ACROBAT installed on your computer in order to be able to open and view PDF files.  (BTW, Adobe ACROBAT is offered free by Adobe and can be downloaded from their website).

AVB-AMG

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12 hours ago, EngineerJet said:

all the joists run the full plan of 20.5'

Ok, so are you sure that the interior wall that runs parallel to the two perimeter walls is also load bearing?
Also, are there any perpendicular wood blocking 2x6's installed to stiffen those long-span 2x6 attic joists, to prevent any bending or twisting?  That is a very long span for a 2x6 joist and probably was only intended to serve the purpose that I explained in my original post in this thread.

AVB-AMG

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19 minutes ago, AVB-AMG said:

@remixer:

I was studying architecture in Manhattan back in the mid-1970's, as part of my junior year "abroad" and remember watching the erection of the structural steel trusses for the Citicorp Center building on East 53rd St and Lexington Ave., since my apartment was just two blocks to the north.  It was really fascinating to see such a large building with the columns at its base, offset from the four corners.  The issue was that the steel members, ("V" trusses), were connected using bolts, instead of being welded, as a cost-savings decision.  The link you provided for the story about the structural deficiency for CitiCorp Center was just a cursory overview of what happened, leaving out some important details.  For those of you who may be interested, (you?), here is a link to a more thorough explanation of the problem and the executed solution.

AVB-AMG

 http://www.engineersjournal.ie/2015/12/08/citicorp-centre-tower-failure-averted/

Yes I know the details of that building. 

My family has been in the structural steel fabrication and election biz since the 60’s 

10 minutes ago, AVB-AMG said:

The attachment to my post is a PDF file.  You will need to have Adobe ACROBAT installed on your computer in order to be able to open and view PDF files.  (BTW, Adobe ACROBAT is offered free by Adobe and can be downloaded from their website).

AVB-AMG

Using phone said unavailable 

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Just now, remixer said:

Yes I know the details of that building. 

My family has been in the structural steel fabrication and election biz since the 60’s 

@remixer:

That is a tough business for U.S. fabricators, especially over the past 15 years, with the competition of low-cost foreign (Chinese) structural steel flooding the market.  Also, having to deal with competition from the concrete industry, since poured-in-place concrete is primarily used for the vast majority of new high-rise residential buildings being constructed in the NYC metropolitan region.

AVB-AMG

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3 minutes ago, AVB-AMG said:

@remixer:

That is a tough business for U.S. fabricators, especially over the past 15 years, with the competition of low-cost foreign (Chinese) structural steel flooding the market.  Also, having to deal with competition from the concrete industry, since poured-in-place concrete is primarily used for the vast majority of new high-rise residential buildings being constructed in the NYC metropolitan region.

AVB-AMG

We did alot of work for private builders. Mta (subway reconstruction and station) along with working with the school construction authority.  We got out of fabrication and erection business about 10 years ago when my dad retired and now only manufacture products for the steel industry. Ie manufacture corrugated structural steel deck. Steel Risers and threads. Base plates etc etc  

another issue was fabricated steel coming in from Canada.

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3 hours ago, AVB-AMG said:

Ok, so are you sure that the interior wall that runs parallel to the two perimeter walls is also load bearing?
Also, are there any perpendicular wood blocking 2x6's installed to stiffen those long-span 2x6 attic joists, to prevent any bending or twisting?

AVB-AMG

Yes the interior wall is load bearing. So with a single 20.5 joist, do I need about 10.25 on each side? Do I need the full 10.25 or can I get away with shorter? (Such as 8.25 or whatever is acceptable) I ask for reasons of getting the wood up there. Manuevering up there would be easier around stairs.

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1 hour ago, EngineerJet said:

Yes the interior wall is load bearing. So with a single 20.5 joist, do I need about 10.25 on each side? Do I need the full 10.25 or can I get away with shorter? (Such as 8.25 or whatever is acceptable) I ask for reasons of getting the wood up there. Manuevering up there would be easier around stairs.

@EngineerJet:

Good to hear that the central interior wall is load bearing.  
Yes, you do need to use the full 10 ft. 3 in. long wood 2x6, attached to the existing 2x6 attic joist, in order to achieve the desired additional stiffness and load bearing capacity.  The new 2x6 needs to also sit on both the existing perimeter wall and interior load bearing wall by at least 2 inches.  I understand the possible added difficulties involved in carrying, maneuvering and setting into place the slightly longer wood members, but that is always part of the challenge of this sort of renovation construction work.  Sometimes, one easier way to access the attic interior is by "treading" the new materials through an attic vent opening in the gable end of the roof.  In that case, you temporarily remove the actual vent and hoisting up the wood members and slide them into your attic.  Just one idea....   Good luck!

AVB-AMG

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3 minutes ago, Ray Ray said:

You are really overthinking this.  

Really.....???   From the guy who recommends using 1/4 inch thick plywood as the new attic floor sheathing.....?  :unsure:

I know that you, or anyone here, can do whatever they want in their home by just trusting their gut and throwing the dice in a "trail & error" approach.  But it is not all that difficult to do the math calculations and figure out what is needed, add a standard safety factor, just to be sure and ultimately, do it right the first time.  I am just making my suggestions based on my knowledge and experience as an Architect.  It is up to the O.P. to decide what he wants to do and how to do it.  As he said earlier, the bedroom that he and his wife sleeps in is directly underneath this potentially new attic storage area.  I think that they both would really like to sleep well and not worry as to whether or not he (they), made the best choice in resolving this issue....

AVB-AMG

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4 hours ago, remixer said:

We did alot of work for private builders. Mta (subway reconstruction and station) along with working with the school construction authority.  We got out of fabrication and erection business about 10 years ago when my dad retired and now only manufacture products for the steel industry. Ie manufacture corrugated structural steel deck. Steel Risers and threads. Base plates etc etc  

another issue was fabricated steel coming in from Canada.

@remixer:

While most of our clients are private real estate developers or institutions, I can empathize with you and your father, having also worked on a number of publicly funded projects for the NYC School Construction Authority (SCA).  The challenge on those projects was that the client (SCA) would establish the project contractual "rules" but would also reserve the right and authority to change them mid-project....  very frustrating.   Also, the SCA would decide whether or not they wanted something to be designed and built, going way beyond what the NYC Building Code mandated, which added to the bottom line construction costs.  Plus, the new schools we did were contracted to General Contractors using the lump sum bid process.  Therefore, it was paramount that the estimators did not forget anything in the bids.  Otherwise, the Change Order process was a real battle and the GC's profit, already paper thin, was at risk.

Growing up, my family spent a number of years outside of Philadelphia, in Chester County.  When I was in high school in the early 1970's, one of my best friend's father worked as an executive at Lukens Steel Company in Coatesville, PA, one of the oldest steel mills in the U.S.  He eventually took the job of President of Phoenix Steel, a specialty steel fabricator.  I remember taking a tour of one of their foundries in Ohio which was fascinating.  Around the same time, we also toured the Bethlehem Steel Corp. plant in Bethlehem, PA, (when it was still in operation), to see how steel was made and then formed into structural steel members, which was a truly amazing experience to watch.

AVB-AMG

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6 hours ago, AVB-AMG said:

From what you have said earlier, the interior wood wall is a load bearing wall so the new, additional 2x6 wood joists would only have to be 10 ft. 3 in. in length and rest at either end on the vertical bearing walls by at least 2" for sufficient load transferring support. 

 

6 hours ago, AVB-AMG said:

That is to augment the existing 2x6 wood attic joists by fastening, (sistering), another 2x6 wood joist to each existing joists, running in the same direction.  When you do this you would offset them in the vertical cross-section by two inches (2”), as illustrated in my basic sketch attached here as a pdf file. 

I see a couple of potential issues here. You're telling him to sister another 2x6, 2" up on the existing joist (by screwing it to the old joist) and to run it full length. Depending on his roof line, he might not have the clearance, as the top of the new joist can hit the underside of the roof sheathing on the exterior wall. Second, all the weight of these new joists are going to be carried by that 2" of existing joist resting on the load bearing walls, instead of increasing it by having BOTH joists rest on the load bearing walls.

If he's going through this un-necessary exercise, he should rest the new joist on the existing exterior wall and center load bearing wall, just like the existing joist, NOT raise it 2 inches. This way, the weight of the attic floor is being supported by BOTH old joist and new joist, resting on the load bearing walls. Then, he can screw the new to the old to increase structural integrity, if he wishes.

To raise the new joist 2 inches, and have to put in tons of screws to fasten it to the existing joist is overkill and a waste of time and effort.

 

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5 hours ago, Sniper said:

I see a couple of potential issues here. You're telling him to sister another 2x6, 2" up on the existing joist (by screwing it to the old joist) and to run it full length. Depending on his roof line, he might not have the clearance, as the top of the new joist can hit the underside of the roof sheathing on the exterior wall. Second, all the weight of these new joists are going to be carried by that 2" of existing joist resting on the load bearing walls, instead of increasing it by having BOTH joists rest on the load bearing walls.

If he's going through this un-necessary exercise, he should rest the new joist on the existing exterior wall and center load bearing wall, just like the existing joist, NOT raise it 2 inches. This way, the weight of the attic floor is being supported by BOTH old joist and new joist, resting on the load bearing walls. Then, he can screw the new to the old to increase structural integrity, if he wishes.

To raise the new joist 2 inches, and have to put in tons of screws to fasten it to the existing joist is overkill and a waste of time and effort.

@Sniper:

While what you are saying seems to make sense, to a lay person, it is not really necessary from a structural perspective, but is sometimes done by some Carpenters in some cases for stability and does not hurt.  I implied that approach in my earlier post, but realize now that I was not clear.  The obvious solution is to insert a small piece of wood under the raised portion of the staggered new wood joist to serve as a so-called "bearing plate" for the new sistered wood joist sitting 2" horizontally on each of the bearing walls, but it is not necessary.  Importantly, it is not necessary for the structural load transfer since the bearing portion of the original 2x6 is still sufficient to accommodate the added load of the attached new 2x6 and, more importantly, the live load of whatever will be stored in the new attic space.      Adding wood blocking between the new "double joists" at the bearing points might be one way to provide additional rigidity, but again, not really necessary.  Also, if the end of the new 2' raised wood joist needs to be chamfered cut at an angle at the top end to clear any sloped roof sheathing then that may be done without compromising the structural integrity of the sistered joist.  If you were knowledgeable about the the structural integrity of wood construction you would understand that what you suggested, while does not hurt, is not necessary to accomplish the structural solution.  But unfortunately, you do not.....  

Your opinion that this is an "unnecessary exercise" and that this approach is "overkill and a waste of time and effort" is your opinion, which you are certainly entitled to have and seem intent on expressing.  But to continue to post your inaccurate and uneducated statements is not helpful to the O.P.  Why you insist on continuing to do that in this thread is most unfortunate and just comes across as belligerent and disagreeable based on your animosity towards me.  You do not have to like me and clearly do not, but don't use your personal hostility towards me to cause you to just act in a childish annoying and irritating manner.  Maybe your real intention of your continued posts in this thread, with your persistent and tiresome naive assumptions of structural engineering, that are either misunderstood or just plain wrong, are also just to provoke a needless silly debate.  Once again, I suggest that you stick to topics that you are more informed, educated and experienced with and not continue to do your "fly-by" ignorant assertions and incorrect statements.  

AVB-AMG

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