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I have the chance to work on a attic renovation on an older house an I have a few questions.
The house is currently 1 storey with a steeper roof 10/12?. The customers would like me to build them a set of stairs leading up to the attic space. The attic is currently uninsulated (blown in insulation on ceiling joists). I will have to frame a stair opening and build a set of stairs to fit. I am a fourth year apprentice carpenter who has done little work on my own and am a little apprehensive about a few things.
1- I am going to have to beef up the ceiling joists (2×6) as the max. span im dealing with is about 12′. A span this great calls for min. 2×8 floor joists. I don’t want to sister 2×8’s to the existing ceiling joists over this span because then I’ll have to furr all the other ceiling joists to bring them up to the same height. Can I just sister a 2×6 on to the joists (12′ span) and hope that they will be strong enough?
2- The customers want a set of stairs that will not squeak and they want to cover them in prefinished oak flooring. What type of stair do you think I should build?
Thanks for any input.
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Chris,
1. ASSUMING that this is truly a single storey with the rafters sitting directly on the top plates of the exterior walls......you can reduce the span requirements by installing jacks between the ceiling or floor joists and the roof rafters. The span is 12 ft. so you set them about 2 feet from the end, reducing the span to 10 ft. on each side. assuming the total span is 24 ft. with a carrying partition in the middle.
as you can see the variables are many when we don't have all the information in front of us.
2. Maybe Stan will get into this one, but laminating layers is not the best idea if you don't want squeaks.
Gabe
*Gabe, Sorry I should have been a little clearer. The Span in question is above the kitchen area. The ceiling joists will become the "new" floor joists for the attic space. I don't think there is any way to reduce the span as the ceiling joist bear on the exterior wall and an interior load bearing partition.
*Chris,On the side of the room where the joist bear on the exterior wall....the space that is normally lost due to clearance, meaning from 0" to about 3 ft. by building what looks like a knee wall along that exterior side, about 2 to 3 ft. from the edge. The space you loose will be unuseable in any event. If your lucky enough that the joist and the rafters line up, you can nail a 2x4 to the side of each connecting them. Know what I mean?What you're doing is transfering some of the load from the floor to the roof rafter.The other way is to sister 2x6 to the existing and this will give you nearly the equivalent of 4x6 joists. Still not the best but will nearly double your loading capacity.Gabe
*Hooking the floor joists to the rafters may not be a good idea, unless the rafters are oversized. You'd be adding a lot of load to them.
*Chris I would double up the ceiling/joist over the kitchen with 2x6, and as Gabe mention earlier, they will become [an almost] 4x6. That should take care of the span, however, you still might have a little spring in the floor. A couple of sure fire methods would be to either sister the ceiling/joist with LVLs or build a flint beam: [2] 2x6s with flat plate steel in between.Now the stairs. When doing stairs, I like to reinforce the stringers by nailing 2x4 to the inside of each [3]stringer... this will eliminate any flex. But most importantly, use construction adhesive when installing the treads. This is were your squeezes will show up.Hope that helps... good luck!!Mike
*I would use 2x8 at least, and take the time to build up the other joists. you will then have less worry about a springy floor. putting a 2x6 alongside another 2x6 does not give a significantly stiffer floor if at all! If you are just starting on your own, the last thing you want to do is cut corners and do things that may catch you later. doing it well the first time is actually the least expensive way to build. your reputation as a good builder is grown with each job.
*Bill,You're right but you're also wrong.2x8 would be better but doubling the 2x6's will probably do the job just as well. It all depends on the way they are installed.I can build a deck or floor out of 2x6s that would be much stronger than a standard one out of 2x8s.Gabe
*Am I the only one who thought this thread was about Janets' older brother?
*ChrisThought of another approach. You might try ripping 3/4" CDX into 5-1/2" strips and making a 2x6 sandwich for the ceiling/joists over the kitchen. This will definitely be stronger than 2/2x6 sistered together.
*I can't believe that no one else has mentioned this yet:you need to talk to a structural engineer.A bunch of guesses from people on the internet is NOT the way to revise the structure of your house!I think it will be a wise investment (they are in the yellow pages).
*Michael,Sorry, but what is CDX??
*plywood - one 'C' side, one 'D' side, eXterior (waterproof) glue -
*kerr, you are right on!! an engineer is a must to do this right and CYA. gabe , how is a 2x6 of similar grade stronger than a 2x8?I know you can build with smaller lumber and get a strong floor, but it involves " engineering "a floor doesn't it?? curious to hear what you are proposing. chris,cdx is "c" grade one side, "d" grade on the other, using exterior grade adhesive to make board.
*Bill,Not a complicated process but it is a meticulous one.You have to start off by exposing the joist from both sides full, wall to wall.Assuming 2x6 @16" centers.You start off by installing 2x6 blocking at both ends and every 3 ft in between. It's absolutely critical that the blocking is complete end to end and without interuption. The fit has to be very tight.Then you install a 5/8 plywood on the top for your flooring and a 5/8 plywood on the bottom for strenght.You make sure all fit is tight, you glue and screw the entire system.What you have is a waffer.You could drive over it with your car.Gabe
*gabe,I thought that was the type of floor you were going to describe! it is very strong. I have tightened several floors by doing the bottom only . it makes a difference.
*The trick is to not allow the wood to torque or bend at all. The layer of ply on the bottom is were the strength is really needed.Floors typically sponge because each piece of joist acts independently instead of "sharing" the load.Gabe
*Chris,I recently ran into the same problem you are describing. I did what Mike Rose suggested, [sandwich of 3/4" ply glued and screwed] worked great.I also have sistered 2x6s with jacks to the rafters. The jacks do put an increased load on the rafters but if done with the sistering should be fine.Getting an engineers input is good advice.