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mbgoss
04-14-2006, 01:34 PM
I have a question similar to Skeltonj's (http://www.homerepairforum.com/forum/showthread.php?t=3801&highlight=attic) regarding adding rolled insulation to an attic with blown in insulation already in place. The replies to Skeltonj answered a lot of my questions, but I have a few complications.

I have a 1960's home in the Kansas City area that has fiberglass insulation blown into the open rafter attic. The attic joists are 2x6's and the insulation is to the tops of the joists for the most part, but some spotty areas. I'd like to add more insulation and noted that when adding to an attic with full joists the insulation should be laid over the joists perpendicular to them. However, I also wanted to lay down plywood to use the attic space for storage.

So, is there any advantage/disadvantage to using thin, high R-value, unfaced, roll insulation BETWEEN the joists that would compact the existing insulation slightly and then lay plywood over the joists? I know that compaction reduces the efficiency of the insulation but didn't know if the addition of high R-value roll would more than compensate for the loss due to compaction.

On a side note... are there any issues with converting the attic into a storage space since it only has 6 inch joists!?

Thanks!

pushkins
04-15-2006, 07:34 AM
Compaction of any fibre insulation always reduces it's R value.
Adding ply wood to a 6" ceiling joist to use as storage is not highly recommended but under some sircumstances can be done.
You must be aware that whatever you put up there in storage it's weight will have a direct effect on your ceiling.
If you want to store a Christmas tree and decorations then that would be okay however if you want it to store books for example then that wouldn't be okay.
If you still want to turn this space into storage then I'd suggest you buy 3/4" plywood for extra strength. As for the insulation problem under where you want to install the ply wood I'd remove the existing blown in insulation and use it to top up other areas in the attic and replace it with hi density insulation, that way you don't need to worry about compaction.

Make sure any added insulation is UNfaced.

Good Luck

mbgoss
04-19-2006, 11:50 AM
Thanks, pushkins. A couple more questions... I see your point about adding more strength by using 3/4" plywood in the attic, but wouldn't that also add a significant amount of weight? Are there any building codes I should be aware of for storage in an attic with 6" joists other that checking with local codes?

I was also thinking of adding a drop down ladder access to the attic where there was not one before? Any issues other than making sure it is well reinforced?

Thanks for your help!

pushkins
04-19-2006, 07:57 PM
There are many codes governing what you can and cannot do in attic spaces, particularly with 6" ceiling joists. Most of these don't deal with the actual homeowner but more so with the construction and intended use at the time of construction. For example if at the time of construction 3/4" ply was laid up there the building inspector would most probably have major problems with the intended purpose of this and the 6" joists supporting it.

Adding the 3/4" ply or sheathing as a sub floor is your safest thing to do, the ply's weight will be evenly distributed across the ceiling joists and will help distribute the weight of anything you put up there. A sheet of 3/4" ply weights around 50 pounds give or take, make sure you screw the ply wood down to the tops of the ceiling joists.

Once again you CANNOT store undue weight up there, so if your thinking about storing boxes and boxes of books and other heavy items think again, this would not be a safe practice, unless you can be sure you can put these items over a wall, which in most homes is very limited.

Most times attics are used in this fashion is to just simply store some seldom used items like Christmas trees and decorations or the like. The house was not built with 6" joists for much more use than this.

As for adding a drop down ladder if it were me I'd be adding by means of sistering and end nailed 2" x 8"'s to at least either side of the 2" x 6"'s that the ladder will be attaching to and make sure that you screw through the 2" x 6" 'sinto the 2" x 8"'s.
The average male is 190 pound that's a lot of weight in one area for 2x6's to handle.

Hope this helps some more

mbgoss
04-24-2006, 12:23 PM
Thanks. I will keep all that in mind as I proceed. I will mostly be storing EMPTY boxes, seasonal stuff, and large, bulky, plastic (and fairly lightweight) kids toys. I have boxes of books that need storing but already decided to leave those in the basement because, even if the attic could handle them, I had no desire to carry them up there!

Would sistering in other areas of the attic allow me to add enough strengh to store slightly heaver things in that particular spot (I'm thinking of about an 8x8 area)?

pushkins
04-24-2006, 07:38 PM
Yes if you sistered for example 2x8's to the existing 2x6's and could get them to span to a wall below so the the 2x8's could rest on that wall then that would do the trick nicely.
In fact if you could get the 2x8" 's to sister and sit on a wall you could store a great deal more "stuff" up there safely.

You cannot tho just simply sister the 2x8 's to the existing 2x6's and expect to increase the load if both ends are unsupported.

My suggestion in this unsupported sistering was for your pull down ladder and I also suggest that the NEW 2x8" 's span as far as possible.