House attic flooring question

[Citation]

This isn't a garage question but I figure the people here would be knowledgeable. My current house is a 1935 brick structure. The attic is good sized but when I moved in there wasn't easy access. Recently I had a set of drop stairs installed so part 1 is done. Next I need to create some flooring.

Currently there is about 12" or so of blown insulation. I haven't measured the actual depth but more than the height of the joist. My original plan was to double the joist with 2x6s placed on top of the originals then add flooring on that. However, I discovered there is actually a floor under some of the insulation. So what should I do?

I don't want to reduce the amount of insulation (the house is already horrid in that regard) so I would prefer not to move the insulation away. Also the existing flooring is just particle board (not strand board) I could put the doubling joists on top of the existing flooring but I am worried about trapping humidity between the layers. I can also pull up the existing flooring, add the extra joist then put flooring down.

Any suggestions? Anything I should think about as I do this job?

 

[WQ59B]

If you think the space between the living space ceiling and the particle board is well insulated, you could leave it and run new 2x6s perpendicular to the existing on top, and insulated those bays. I wouldn't think moisture would be an issue, but every house is different. Only thing to consider is you said the particle board is "under some of the insulation"- would it be an issue to have different height new joists? You could rip them to go over the particle board, allowing a level 2x6 surface in case you wanted to plywood over that.

Personally, I don't like not being able to get to the top side of the ceilings for any ductwork, wiring, etc., so I would rip the particle board out.

 

[The Cobbler]

when I added insulation in my house, I built joist trusses for lack of other words.
I cut (forget the measurement now ) approx 14" pcs of 2x4 and fastened them every 16" perpendicular to 14' 2x4s then fastened that assmbly to the tops of the existing ceiling rafters . after the insulation was done I screwed 1/2" ply on top for a walking surface.
this is only for storage , it's a bit spongy because of the 1/2 ply but serves my needs well

 

[NUTTSGT]

What's the reasoning for putting flooring up there ?

 

[Citation]

The HVAC system in the attic uses flex ducts so they would stay on top of any flooring. I would also screw the panels down so they could be pulled back up if needed. The intent is only for storage. To be clear, "flooring" in this case only means something to walk on, put things on. I don't intend to make this living space of any sort.

 

[NUTTSGT]

Depending on what you want to store, it might be much easier to get a storage shed in the back yard.

Better yet, how about a larger shed with a loft area ?

 

[Citation]

Depending on what you want to store, it might be much easier to get a storage shed in the back yard.

Better yet, how about a larger shed with a loft area ?

Not possible with my property. I simply don't have the space for it. I have been thinking about a new garage build but for other reasons I've put that project on long term hold. The attic on the other hand has perhaps 1000 sq ft if you could use all of it (can't/don't intend to, BTW the back yard is about 1000 sq ft - it was not my idea to live on a small lot!). It also has good clearance (appears to be 12ft+ at the peak and plenty of space over 6ft). What I'm looking to store is primarily things like the Christmas decorations, kids toys, some household goods, a table and chairs my wife won't part with etc. Most of what I want to store is bulk rather than weight. I do know where the load walls are so the few heavy items will be placed over those walls.

 

[rsanter]

Perhaps you should insulate the walls and under the roof af the attic to make the space closer to the conditioned space of the house

 

[Miss the Pontiacs]

Perhaps you should insulate the walls and under the roof af the attic to make the space closer to the conditioned space of the house

This makes sense to me.^^^^^^^^^ Also you gave the impression you need all the insulation possible. Your heating flex pipe sit on the cold side of your insulation?? Am I getting this right. Your Hvac should be on the warm side. I would run these in the existing joist runs. Then you could do some perpendicular joist runs and insulate. This would save on heating costs. Allowing you to build a separate shed as NUTTSGT had suggested with the money you saved.

 

[Citation]

Looking on line it looks like most recommend running a second set of joists perpendicular to the ceiling joists. Insulating the underside of the rafters is an idea I'll look into. The issue I have with the current flooring, such as it is, is using it would cut my insulation in half. This is why I'm asking about ways to put a floor down without reducing what is already there. I will look into ways to improve the flex ducts but putting them in the rafters is likely a bigger job than I want.

Again, a back yard shed etc is a nonstarter. We don't want to give up that space (even if it meant no extra storage).

 

[WQ59B]

Insulated flex duct is fine on the 'cold side'- completely common practice. Depending on the size of the ducts, perpendicular new joists may well disallow running them in the bay anyway.

 

[Miss the Pontiacs]

I guess our climate is considerably colder where I am located. Never heard of placing basically heat on the cold side of the insulation. I guess we would have to heat up the cold pipe and then finally heat up the building. My ceiling is made up of first drywall then a vapour barrier and then insulation and lots of it. The fewer protrusions through the vapour barrier the better. Heat is money as the OP alluded too.

 

[jetnow1]

Most of us in cold climates have basements where the heat system is installed. Most warm
weather areas do not dig down for basements so the heat/ac runs thru the attic. If I was
in the original posters situation I would build a raised catwalk down the center which would have foam insulation inside it to keep the insulation levels, then put collar ties
between the rafters with plywood shelves to hold the storage. This keeps the insulation levels and does not have the existing insulation compressed by the stored items.

 

[lakeroadster]

This isn't a garage question but I figure the people here would be knowledgeable. My current house is a 1935 brick structure. The attic is good sized but when I moved in there wasn't easy access. Recently I had a set of drop stairs installed so part 1 is done. Next I need to create some flooring.

Currently there is about 12" or so of blown insulation. I haven't measured the actual depth but more than the height of the joist. My original plan was to double the joist with 2x6s placed on top of the originals then add flooring on that. However, I discovered there is actually a floor under some of the insulation. So what should I do?

I don't want to reduce the amount of insulation (the house is already horrid in that regard) so I would prefer not to move the insulation away. Also the existing flooring is just particle board (not strand board) I could put the doubling joists on top of the existing flooring but I am worried about trapping humidity between the layers. I can also pull up the existing flooring, add the extra joist then put flooring down.

Any suggestions? Anything I should think about as I do this job?

I'm confused? There is 12" of insulation and particle board flooring. How tall are the existing joists

 

[Citation]

I'm confused? There is 12" of insulation and particle board flooring. How tall are the existing joists

To be honest I didn't know the particle board was there until after the stairs were installed. When you look at the attic you only see the blown insulation. It's think enough to cover the joists by several inches.
So here is my guess. The original joists are something like 6 or 8 inch (I haven't measured). They had a floor put on them with insulation between all under the floor. That was perhaps 6 or 8 inches (height of the joists). Later more insulation was added. They didn't pull the old floor, just added on top of it. Installing the steps gave a bit of a cross section view of things.

 

[Falcon67]

I would consider what you already kinda mentioned - run some 2x6 or 8 perpendicular to the existing joists to spread the load, then cover with 7/16" OSB. You can run them 24" OC and not have to worry about the OSB sagging. Depends on how much space you need but 2 or three sheets worth would not be much of an issue. 3 sheets give 16 sq/ft of area.

 

[lakeroadster]

Lets not throw new material, money and labor into a bad plan.

Give us some more information so this can be some what engineered vs proceeding with nearly no information that is needed.

1. Is this a truss supported roof of are we talking rafters and ceiling joists?
   
2. What is the span for the trusses or ceiling joists?
   
3. Are the existing truss lower chords (or ceiling joists) one piece, or spliced?
   
4. What are the size of the truss lower chords (or ceiling joists)? This needs to be known.
   
5. How much weight are you wanting to put in the space (lbs / sqft)? 15, 20, 25, 30, 35, 40?
   
6. What are the existing wall structural components made from? (block, 2 x 4's, 2 x 6's or ?)

Putting the new joists perpendicular to the existing is not a good idea. Any deflection will be added to the existing structure. What you want ideally is to leave the old structure alone, and a structure that will carry the new load.
That means removing the existing insulation and decking, adding the new supports, insulating, and then adding the new decking.

And even that may not work well, depending on the answers to the above questions.

Just trying to help.

 

[Citation]

In the next few days I'll try to get up in the attic to get some pictures, measurements and general assessments.

I'm not planning on heavy loads and I do have the benefit that I can place heavy items on the load bearing walls that are under a portion of the attic. But most of what we want to store is light, bulky items.

 

[Kaizen]

Sorry to say i'd do more research as you said you would. most likely that floor is not fully insulated. Under my blown in I found a lot of wiring so watch out. I'd clear the space with a leaf rake and a good mask.....this stuff is nasty dirty after all this time. I'd also make sure they did not use asbestos insulation (look it up) and then put that floor there to cover it up which technically makes it safe. go to the ceiling and see what you need. you will need to frame what you are doing on 2 foot spacing as that's the most width you can probably get up there in plywood. good time of year to do it before it gets hot as hell up there.

 

[Citation]

Thanks for the heads up on the asbestos. I'm going to have to investigate in more detail but the material I've seen thus far looks like blown fiberglass but I will take some precautions until I'm sure.

 

[James-W]

I tend to think if you do this right and do it to code, it will most likely cost you a whole lot more money than you ever imagined.

 

[Citation]

I'm sure making it a living space floor is expensive. I'm not at all convinced that adding a storage floor needs to be.

 

[lakeroadster]

I tend to think if you do this right and do it to code, it will most likely cost you a whole lot more money than you ever imagined.

I'm sure making it a living space floor is expensive. I'm not at all convinced that adding a storage floor needs to be.

"Code" means designing the space regardless of use, be it for storage or as a living space.

FWIW, here's what's there currently, assuming 1/2" particle board, 5/8" drywall and 12" cellulose

Particle board weight, 1/2" = 2.3 psf
Drywall weight, 5/8" = 2.31 psf
12" cellulose insulation (8.5" = .97 psf) = 1.37

Current load on ceiling joists / lower chords = 6 psf

Since there is already drywall, decking and insulation the labor to tear all this down and start over is going to be pricey.. I think James-W's comment is on the mark.

 

[mike93lx]

Insulated flex duct is fine on the 'cold side'- completely common practice. Depending on the size of the ducts, perpendicular new joists may well disallow running them in the bay anyway.

Common doesn't mean it is smart.

 

[niget2002]

Common doesn't mean it is smart.

Common changes depending on location in the world.

We don't even have basements here.

Regarding the flooring, I think you're putting too much thought into it. It's an attic.

Throw some cross boards up there and stick some plywood/osb on it.

The house I'm in has horrible attic space. We were lucky that it has a very large closet under the stairs where we can hide all the Christmas stuff. I also built a bunch of shelves along the ceiling in the garage for what didn't fit under the stairs.

Regarding the kid's toys and the table... If they're not being used... get rid of them. Let someone else enjoy them. Unless you plan on getting a house one day that you can actually use the table and chairs. I will say an attic with large temperature/humidity swings throughout the year is not the best place to store nice furniture.

 

[Citation]

The kids toys get cycled so we don't expect that to be permanent. The table and chairs are wife's grandmother's. Not my call.

 

[Falcon67]

Common doesn't mean it is smart.

You'll not find anything else in these parts. Flex is it except in some commercial applications. You don't see even high end $500K up builders here using solid ducting. They just use bigger flex ducts to cut the noise. 500K is a good sized house - easily 3000 sq/ft or so.

We've got 4 sheets of OSB over the garage ceiling and plenty of stuff stashed up there. I have about the same in the shop, a good 1000lbs of material up there - bumpers, all the electrical piece/wire storage, misc car parts and "stuff".

 

[Crazyjake8493]

I wouldn't go through the trouble of insulating the rafters and making the attic a conditioned space unless it was intended to be converted into additional living space.

For quick and simple storage, just make a simple frame with 2x6's or something, run them perpendicular to the existing joists, and throw a couple sheets of plywood on it. Easy peasy. Don't overthink it if it'll just be used for decorations.