# Floor Joists in Attic



## cibula11 (Dec 9, 2006)

I am in the beginning stages of remodeling my unfinished attic for a nursery and small office.  After starting to insulate I realized my floor joists we true 2x6's that spanned 20 feet at their widest point.  The majority of the room, the span is 15 feet.  The room is obviously a bit bouncy.  Should I stop and fix this, or am I okay to continue?  Suggestions.  I have considered sistering the joists but I have heard this is pretty complicated.  Also could add a beam below, but it would not be able to be in the middle of the 20 foot span, and of course the living room below is finished.


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## Daryl in Nanoose (Dec 9, 2006)

So what would be the span if you put that beam in downstairs and what is the spacing of your 2x6 now? A few pics and or drawing would help us out here.


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## glennjanie (Dec 9, 2006)

Welcome Cibula:
I would not recommend using the portion of the attic which spans 20' for anything but storage for Christmas decorations or empty boxes we save to send electronics back in (in case they fail in our lifetime). In portions of the attic where the span is not so long I would consider tying the joists to the rafters and perhaps even some sort of truss configuration from the attic wall line to outer perimeter of the house. Also, I would not drive any nails in the developing space; consider screws as fasteners instead, because the pounding of nails might cause ceiling cracks and nails to pop below. The spongey joists are going to make it hard enough on the celings below. The sistered joists are hardly ever a workable solution because they must rest on the outside walls to be effective; again screws would be in order rather than nails. I would not use the 20' span even if it were sistered with 2" X 12" joists; wood is just not that strong. The span should be broken up with ties to the rafters just to support the ceiling.
I do admire your effort to use space that already exists; some attics seem to be such a waste of enclosed space. I just think this job requires more engineering. Please post back and let us know how it turns out.
Glenn


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## cibula11 (Dec 9, 2006)

The 2x6's are 16 o.c.  If I were to put a beam in below.  There would be one span of about 8 feet and another at 12.  The house was once a one room school house that has been added on to.  So, if I were to sister with 2x12, those joists would go from exterior to exterior (the old exterior, which is now the wall that seperates the new addition to the old).


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## Square Eye (Dec 10, 2006)

My humble opinion.. 

The beam would be more effective and less trouble than sistering 2x12s in. When you start trying to sister in the joists, you will find that you will have to remove a portion of the roof and slide them in from outside. It is physically impossible to get a ceiling joist in the space from inside. You will get one end in a space, then the other end will hit the rafters and joists and will not make the turn to drop into place. Trust me on that LOL
Even at 12' span, the beam would be effective. The 2x6's though would be marginal for a 12' span in a living area.
But, houses built before 1970 often have true 2x6 floor/ceiling joists. It's been done before..
Make sure you provide adequate support under the ends of the beam. You will need at least 3 studs under each end and make sure the studs are sitting on a framing member under the floor. Bridging from the exterior wall to the next joist, or center it over a floor joist.

Anyway.. good luck!
Welcome to the forum!


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## Daryl in Nanoose (Dec 10, 2006)

I agree with with tom 100%. Going with a beam below is going to be a lot less hastle.


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## cibula11 (Dec 10, 2006)

What should I use for the beam.  In the past I have used 2 2x8's together.  Would this be sufficient?  If I could get away with something smaller that would be great.  I just would rather not have a 12" beam breaking up my living room ceiling.  Also, the distance of the beam would have to be around 15' (I haven't measured exactly).   Can I buy lumber that long?  So, to make sure this is what I am hearing from all of you, let me paraphrase.  If I ran a beam from the gable end exterior wall to a wall in the middle of the room, I would give myself enough support?  Thanks for the feedback, it all helps.


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## glennjanie (Dec 10, 2006)

It is possible to strengthen a beam with steel plate sandwiched in between 2 wooden members with a bolt every foot staggered from top to bottom. You can visit a steel supplier and ask for the engineering department to tell you what to use. I'm betting it will take at least a 2 X 10 to bear the load; that is, a 9-1/4" X 3/8" steel plate between two 2 X 10s with the bolts and firm support on each end like Square Eye mentioned. Then, with the shorter spans in the attic, you can tie the 2  X 6s to the rafters above to help bear the load and make it pretty well.
Glenn


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## Square Eye (Dec 10, 2006)

You also might consider a steel I beam.
You can get more span, more load bearing capacity in a shorter, more narrow beam.
Wrap it/box it in, with 1x whatevers and forget it.. 
Be sure you have about 10 people who can help you set it though. 
Steel gets very heavy very quickly!


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## Daryl in Nanoose (Dec 10, 2006)

Alwright Tom, stop reading my mind. 
ibula11 you may want to call a truss company and see if there is a Laminated beam they can make for this of course it would be thicker but maybe not as wide. Just a thought...


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## cibula11 (Dec 11, 2006)

Any ideas on a ballpark estimate of the cost involved in some of these solutions.  I also was given an idea of using some 6x6 timbers that could be exposed.  I guess, I am looking for a simpler solution due to having to complete this project in an already finished room.  My biggest issue now is deciding the best place for this beam.  I have a ceiling fan in the middle of the room, which would be the obvious choice for support.  I think I may just go to one side or the other.  If I were to do a steel I beam, could I still use 2 or 3 studs together for support, or do I need to use something else?


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## glennjanie (Dec 11, 2006)

The 6 X 6 timbers will only give as much support as 3  2 X 6s nailed together; that is not enough support. Moving the support beam in the direction of the 12' span is a good idea. The steel I-beam will be much more expensive than the 3/8" steel plate sandwiched between 2  2 Xs and bolted together which will also give you a place to nail finish materials. Yes, the 3 studs on each end will provide sufficient support; just remember the 2 X 4s need solid support below them also. Just the subfloor is not enough to hold them. Ask the engineer at the steel supplier's how tall the beam should be; its a free service at most suppliers.
Glenn


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## cibula11 (Dec 11, 2006)

Thanks.  The span longest span is 20'.  There is a bathroom wall that makes the majority of the span around 15'.  One end of the beam would go to the exterior, gable end and the other support would rest on a 2x4 bottom plate that currenly supports a wall in the middle of my house.  I think underneath the living room floor is a center beam or cinder block colums that support the span from the basement of the house.  (Its kind of a weird house because it was once a school house that was moved to its current location).


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## cibula11 (Dec 11, 2006)

Or what about lvl? size?  I was looking at 1 3/4" by 9 1/4".  Would that work?  How about I ask this question.  If it was your home that had 2x6 floor joist that span 20', What would you do to support this so that you could finish the attic for a nursery or offce?


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## glennjanie (Dec 11, 2006)

I would do my best to get a beam in the center of the span; cutting it down to a 10' span on each side, I could live with that. Then, I would also install my side walls in a way that would tie the joists to the rafters which would shorten the span even more and stiffen things up considerably. Then, I would try to use the lightest materials available in the attic. For instance, 3/4" tounge and groove underlayment grade plywood glued with PL 400 and screwed every foot, mimimum (extra layers or the osb type underlayment would be much heavier). I would insulate the roof space and the walls of the new attic and cover both with 1/4" luan paneling, glued and nailed. For a finish on the floor, maybe some laminate flooring.
I would still check with the steel supplier on the beam using the 3/8" steel plate sandwiched between 2  2 Xs with lots of bolts and support it on each end with the 3  2 X 4s which would be bearing on outside walls or piers to support the floor under the end posts. I would make the access to the attic by a spiral staircase, there is a steel one that would add very litttle weight made by The Iron Shop and advertised in The Mother Earth News.
I am still open to questions or other suggestions.
Glenn


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## cibula11 (Dec 12, 2006)

I looked in my living room and I think there is a way where I can put the beam directly in the middle, which is good.  There is already a staircase going upstairs so that's not an issue.  Previously I bought sheetrock for this space, with the assumption that it was up to code since it was assessed as having a finished attic.  Would putting sheetrock on the walls and ceiling be a problem?  My issue is that I have a lot of it and I bought it about 6 mos. ago.  I have 5/8" for the ceiling and 1/2" for the knee walls.  Since this space was used for a room previously it already has knee walls (some of the studs used are tied to the rafters).  I was thinking we would probably carpet the room.  There is already a subfloor laid, but I'm not sure of the thickness.  I know its not very thick, but it doesn't weigh much either.


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## glennjanie (Dec 12, 2006)

In my opinion the sheetrock will be too heavy for this application. I understand your feelings about already owning it though, I like to use what I already own too.
Glenn


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## cibula11 (Jan 3, 2007)

I was thinking of using tongue and groove carsiding for a ceiling.  Would this still be too heavy?


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## glennjanie (Jan 4, 2007)

The wood siding would be consideably lighter than 5/8" sheet-rock. The knee walls need something that will give lateral stability--something glued and screwed to the studs, thus causing the load to be distributed over more joists. I'm anxious to see pictures of your project.
Glenn


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## cibula11 (Jan 5, 2007)

I'm anxious to see it turn out as well .  I will try and post some before and after pics.  This weekend I am finishing the insulation and hopefully will get started on some other aspects of it.  I am waiting for help with installing the beam and trying to find the best price of carsiding.  I think my premliminary estimates are upwards of 250 for the entire ceiling.


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## MOLSON (Jan 8, 2007)

A couple things.

1.  Is there blocking in between the floor joists?  if not, add some.  it will help stiffen up the floor quite a bit.

2.  What do you currently have for a floor?  You may want to think about using T&G Plywood sub flooring and then carpet over that.  It will add a bit of weight but it should stiffen things up a lot.  Make sure you lay the plywood so the length runs with the floor joists.

As for the 2x6&#8217;s if the actual dimensions are 2" by 6" then they will be almost as strong as a current day 2x8.
Also, there might be 1 or 2 floor joists that are cracked at a knot which is causing bouncing in a large section.  Half of my living room used to bounce a bit when we moved in.  Turned out I had 2 floor joists that had cracked on some knots and it affected the floor covering about 6 joists.  I cut some 3/4" plywood into strips and screwed one to each side of the cracked floor joists and my floor is stiff as can be.

Molson


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## cibula11 (Jan 8, 2007)

There isn't blocking...I would assume.  I will take up the old subfloor and add some though.  The subfloor now is true subfloor, but it is older.  I'm guessing it has to be at least a 1/2 " to 5/8" thick.  It is in 4x8 sheets.  Any suggestions  then for a beam?


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## MOLSON (Jan 8, 2007)

many places that sell beams, either LVL or I Beams usually have charts and guides that will tell you exactly how big a beam needs to be.  

You may also want to give a call to your local building permit dept.  Yes, you will probably have to buy a building permit then, and have it inspected but for something like this, that's a good thing.  Just think about what might happen if you put the beam in the wrong place or don't support it properly and the second floor collapses after you move in all the furniture.  Or in the future when your then 3 year old is using the bed as a trampoline.  Guess what... People could get hurt and your home owners Insurance might not and probably won't give you any cash to rebuild.


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## cibula11 (Jan 8, 2007)

The big issue i have with the building inspector, is that the area (attic) was already assessed and coded as finished.  The previous owner used the space as a bedroom and supposedly there was a ton of crap in the space...so I'm assuming a fair amount of weight. I have jumped up and down and it is springy, but no cracks or anything below....just some deflection.  I already put a beam in one area of another room (same issue just a shorter span for the beam), and it totally solved the problem.  I know a beam will do the trick in this space as well, but I don't want to put a huge 12" beam in the area if I can get around it.


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## Square Eye (Jan 8, 2007)

Steel is the only way to get by with a beam closer to the ceiling. No wood product, engineered or otherwise is going to span that far without deflection unless you go to 12" or thereabout.


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## Daryl in Nanoose (Jan 10, 2007)

I am still with Tom on this one, Steel I beam all the way. One note the 2x's used to support the beam have also got to be supported under the floor to concrete footing.


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## cibula11 (Jan 11, 2007)

I think I'm going with 2 lvl's.  It will be much cheaper this way and not near as heavy.  My one end of the beam will be supported by the foundation wall.  As for the other end....I checked in the basement and the position of the support will about about 3 ft. away from the main beam that supports the majority of my house.  Will this be close enough to give support?

You mentioned using supports with wood.  Is there a different method with using steel?


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## cibula11 (Jan 11, 2007)

It would also sit on a floor joist.  (My floor has several layers of hardwood, so it is needless to say very sturdy).


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