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rustic 02-27-2009 06:45 AM

old house attic questions
 
My house is about 50-70 yrs old. It's a 1 story with not a very tall attic, barely 6ft under the ridge in most areas.

My overhead joist are made from old 2x4's spaced approximately 2ft centers. I want to put at least R19 insulation. I want to make the insulation cavity deeper. should i stack a 2x6 on top of the 2x4 joists or put a 2x6 or 2x8 on the side of it like sistering?

On the sistering option would it matter if the insulation doesnt sit flat because of the 2x4 being in the way?

I do not want to blow in insulation. thanks

DangerMouse 02-27-2009 07:22 AM

blown-in cellulose certainly makes more sense, however, since you don't want it, perhaps use some osb engineered floor joists instead of 2x? that way, you could lay them on top and just drive a few screws througn the solid wood runners to the 2x4's underneath? you could even rip them down the middle to get twice as much, since you don't need them THAT tall?

just a thought.

DM

Scuba_Dave 02-27-2009 07:27 AM

Are you taking the ceilings down to add the insulation?
Or adding from the attic?

If adding from the attic just add the insulation
Then fill in where the studs are
If you want to walk/move around in the attic then its a good idea to add some wood so you can walk

rustic 02-27-2009 07:57 AM

i want to add wood so which way would you suggest?

DangerMouse 02-27-2009 08:00 AM

in that case, i wouldn't go my way unless you left them whole. split, they would be too weak, i should think.

DM

Scuba_Dave 02-27-2009 08:04 AM

Quote:

Originally Posted by rustic (Post 237568)
i want to add wood so which way would you suggest?

Adding wood in the attic? Or taking the ceilings down & adding from underneath? Do you have 2x4's or a 2x4 truss system - probably joists since they house is over 50 years old. Are the rafters 2x4 also?

What distance do the 2x4's span from outside wall to a supporting inside wall? Is there any insulation up there right now?

Depending upon the setup I would be inclined to add 2x8's 16" OC

rustic 02-27-2009 09:45 AM

Scuba Dave
Adding wood in the attic?(yes) Or taking the ceilings down & adding from underneath?(no) Do you have 2x4's (yes)or a 2x4 truss system(no) - probably joists since they house is over 50 years old. Are the rafters 2x4 also(2x6)?

What distance do the 2x4's span from outside wall to a supporting inside wall?(about 14ft) Is there any insulation up there right now?(only about an inch of really old blown)

Depending upon the setup I would be inclined to add 2x8's 16" OC (How would you go about that? I am not sure if i should run them along side of the old joists.


Dangermouse: I have seen those engineered joists on TV (good idea BTW) but not around here(S. Louisiana) I was thing of making them but i dont think i would have the time. Are they more expensive than a 2x8 of the same height?

thanks guys

DangerMouse 02-27-2009 09:53 AM

i'd think they would be cheaper, but i've never used them before, so i have no idea really.
but a tablesaw would make them easily enough, since what you intend does not require them to be engineered to hold excess weight.

DM

Scuba_Dave 02-27-2009 11:03 AM

Well if you are adding from the attic & not taking down the ceilings I would be inclined not to add any wood. I would simply add insulation across the ceiling
If there is a wall/supports near the middle of the house I would use that to support plywood to work from. Then slide the insulation out over the ceiling

I'm actually doing this at my MIL's house. She has the same setup but without any insulation

I would also go to R30 if you are in a cold region

jogr 02-27-2009 11:21 AM

Why is it that you want to add wood? Those 2x4 ceiling joists at 14 ft span won't hold much weight. If you want to add wood to make a storage area then you should be considering beefing up the 2x4s by sistering something bigger to them instead of stacking on top of them.

rustic 02-27-2009 11:31 AM

jogr,

I dont want to add storage. i want to increase the depth of the cavity that the insulation will lay in.

I dont want to just lay insualtion up there because if i need to get up there and do work i dont want to trample all of the insulation i put up there. I am experiencing this catastophe in a section of the house already.

Scuba_Dave 02-27-2009 11:46 AM

Ok, then you need to add the wood for support
A 2x8 24" OC will not span 14'
A 2x8 16" OC will span 14' - just barely depending upon the wood
I would consider 2x10's if you are going to store anything up there

I would put them 16" on center (OC)
This is going to be a real pain to nail them at the outer edges
A nail gun would make this much easier unless someone has another idea?
Measure from the outside wall towards you access point (attic stairs) & mark every 16". Then I would start installing from the access point & work my way out to minimize walking on the 2x4's
Cut plywood to secure between the 2x8's as a walkway

jogr 02-27-2009 02:48 PM

Quote:

Originally Posted by rustic (Post 237696)
jogr,

I dont want to add storage. i want to increase the depth of the cavity that the insulation will lay in.

I dont want to just lay insualtion up there because if i need to get up there and do work i dont want to trample all of the insulation i put up there. I am experiencing this catastophe in a section of the house already.

I've got a better idea. Forget the wood and blow in about R45 of cellulose and vow to never go up in that attic again. Attics are hot, and those roofing nails like to poke you in the head anytime you go up there. If you get the urge to go in the attic go fishing instead. I guarantee you'll have more fun.:thumbup:

Thurman 02-27-2009 02:57 PM

If you are only wanting to add some storage space in the attic, do you have a hallway that is approximately in the middle of the house? You could lay/secure plywood or OSB on the joist only over the hallway for storage, too much attic storage results in too much stuff being put up there. As far as insulation, I have added to my last two houses by laying batts perpendicular to the run of the joist. This is recommended by the three (3) electrical utilities in our area. By laying it this way they preach that you actually create an air gap between the present insulation and the new insulation that creates more energy efficiency. Thanks, David


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