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-   -   Furring out existing 2x6 rafters (http://www.diychatroom.com/f19/furring-out-existing-2x6-rafters-133391/)

kirylm 02-11-2012 06:03 PM

Furring out existing 2x6 rafters
 
My house was built in 1941. It's 1.5 story with regular gable roof. We are planning on renovating our 2nd floor. I have few questions about the approach i have chosen.


http://i39.tinypic.com/5khq90.gif

http://www.freeimagehosting.net/lj5i1http://www.freeimagehosting.net/7tb5aExisting rafters are 2x6 and 15' in length, span is 14'' o.c. The floor joists are 2x8 and joined from two pieces in the middle (each joist basically consists of two pieces). They are 12' in length (each, making total length of a bit less then 24'' because they overlap like 5''). I attached the picture. There are 2x4 collars nailed every other rafter.

I am planning on furring out rafters and ridge board with 2x4 douglas firs, creating an air channel (smth like 1'' from sheathing) along the space between rafters by using plywood wrapped in radiant barrier foil (exterior side), then putting unfaced R-30 insulation and plastic sheeting for for vapor barrier.

I will use simpson hardware. 3x7, 16ga plates for rafters, 6x2 12ga angles for reinforcing rafters to the ridge board, 9x1.5 16ga angles for reinforcing rafters to the floor joists.

Then, since i am adding weight to the rafters, i am planning to reinforce floor joists in the place where they connect together in the middle. I am thinking of using some simpsons plates and corners, and/or bolting them together.

I will be putting new subfloor using 4x8 boards, and then nailing hardwood floor. Also plan to add some knee wall cabinets.

Here are the questions:

1). By furring out rafters I will add weight to the roof structure (wood + metal plates & corners + plywood). Does this pose any structural problems? Should I reinforce the floor joists better (extend it with 2x4, etc.) then with just some hardware metal plates and bolts?

2). By removing collar beams I potentially increasing outward thrust, however, i don't think that those are helping much. The floor joists is really holding those rafters together. Therefore I plan to reinforce those joists. Question is: from what i described above , does it sound reasonable?

Thanks

joecaption 02-11-2012 06:17 PM

I'm missing something, is your plan to take out that center supporting wall and the ceiling rafters to make a catheral celing?

kirylm 02-11-2012 06:20 PM

no, no cathedral ceiling, i am keeping the floor. the picture's dimensions is not exactly correct, the height (from the ridge to the floor) is about 10'.

joecaption 02-11-2012 06:22 PM

Looks like an attic not added living space.
How far is it from the tops of those rafters to the center of the ridge beam?

kirylm 02-11-2012 06:23 PM

right, its an attic, but its finished to add living space.

kirylm 02-11-2012 06:27 PM

Quote:

Originally Posted by joecaption (Post 850823)
Looks like an attic not added living space.
How far is it from the tops of those rafters to the center of the ridge beam?

if i understand correctly, you are asking about the height in the middle from where rafters intersect with ridge board to the floor joists? then - its about 10 feet.

Joe Carola 02-11-2012 08:33 PM

Quote:

Originally Posted by joecaption (Post 850815)
I'm missing something, is your plan to take out that center supporting wall and the ceiling rafters to make a catheral celing?

Joe,

You mean ceiling joists....right?

kirylm 02-11-2012 08:35 PM

I am not removing ceiling joists

Nailbags 02-11-2012 09:11 PM

"long the space between rafters by using plywood wrapped in radiant barrier foil (exterior side), then putting unfaced R-30 insulation and plastic sheeting for for vapor barrier"
Why are you placing a vapor barrier in? you don't need it in the attic except were the ceiling is and that is were the Kraft paper needs to be face down towards the living space. doing it from what you described sounds like your going to trap moisture.

kirylm 02-11-2012 09:14 PM

right, the ceiling will be right on the rafters. i will be putting drywall on top of that plastic vapor barrier, so it will be facing living area.

Nailbags 02-11-2012 09:34 PM

Quote:

Originally Posted by kirylm (Post 850945)
right, the ceiling will be right on the rafters. i will be putting drywall on top of that plastic vapor barrier, so it will be facing living area.

Don't just use the Kraft faced batts it is a whole lot better. the Plastic is how can I say like placing your head is plastic bag and expecting to breath fresh air! if you do that you get water vapor on the plastic and in contact with the sheet rock and then you get mold. and damp sheet rock and more problems. I just wish who ever came up with placing plastic sheathing over insulation would be around to to repair the moisture damage it causes.

kirylm 02-11-2012 09:36 PM

Quote:

Don't just use the Kraft faced batts it is a whole lot better. the Plastic is how can I say like placing your head is plastic bag and expecting to breath fresh air!
thanks for the advice

still my other questions are unanswered

Nailbags 02-11-2012 09:42 PM

your floor joists are 2x8 correct? can you read a lumber stamp? if you can can you tell me what kind of lumber it is? is it Doug fir larch? or Doug fir?

kirylm 02-11-2012 09:43 PM

Quote:

Originally Posted by Nailbags (Post 850982)
your floor joists are 2x8 correct? can you read a lumber stamp? if you can can you tell me what kind of lumber it is? is it Doug fir larch? or Doug fir?

hmm.. i doubt that I will get that, but i will definitely try. does it matter that much?

Nailbags 02-11-2012 09:48 PM

yes it does I can give the formula for the tinsel strength of each types of wood and how much they can hold. Doug Fir Larch is the strongest, then Doug fir then Hem Fir then southern white pine then yellow pine the weakest.


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