Attic Flooring Questions
 

I’m in the process of planning out completion of the attic floor in my 1895 house. Right now it has joists with several areas of plywood or fiberboard nailed in place for access to some areas. Nothing is consistent. The rest of the floors in the house have the original wooden planks, with decorative wooden flooring on them, usually oak and birch.

I am wondering what is considered the proper base material and thickness, keeping in mind that a another layer of wood flooring will eventually be placed on it. As this is the third floor, am I wrong to be keeping in mind the weight of the various thicknesses of flooring as well?

Thanks!

What size are your joists, and how long is the span?

Dionysia, don't forget to ask what the joist spacing is too, before performing your calculations!

Attic Joists
1.75" x 5.5" actual
length varies; many are hidden by insulation. 6, 7 + feet

Spacing is 14" (side to side, not center to center)

Attic max Width
362.5 inches
30' +

Attic max Length
402"
33.5'

Another factor is that it might be pretty tough to get anything larger than 4' x 4' sheet of plywood into into the stairwell because of a sharp turn into the stairwell before going up the stairs. Gotta love these old Victorian houses and their quirky design!

Thanks,

vince

[blushes] I am impressed that you think I could do the calculations, Bridgeman! As you know, we are dealing with similar issues on our infamous moneypit...

Dionysia, I've heard they sell face make-up that should easily cover the blushing. So go ahead, and calculate away!

But to answer the OP's attic flooring question, if the joists are only 2 x 6s, they obviously have some support from load-bearing interior walls in the living space below. I'd suggest using 3/4" T&G for a uniform subfloor, glued and screwed, followed by a finished floor of choice. By far, the heaviest loading the attic is likely to see will be from interior walls, furniture, storage items and people. Total flooring/support deadload is usually computed at around 10 PSF (3/4" plywood weighs just 3 PSF), while other applied loads are usually figured at 40 or even 50 PSF, total. Heavier design loads (80 PSF) are usually used for exclusive storage areas.

Thank you. Mr Bridge.

The attic does indeed have an I-shaped load bearing interior wall underneath it that extends to the outer walls. The flooring in the other two floors is also 3/4" T&G. I've also thought it was be good to screw it down, less plaster dislodging impact shock than nails and better holding power. Any preferences on glue type or brand?

Thanks,

vince

You can buy adhesive made exclusively for subflooring, in the large (30 oz. tubes) at commercial construction supply places. If it weren't so cold outside, and late in the early AM, I'd walk out to the shop to tell you what I've been using. It's probably a tad better than Liquid Nails, which is available in all the big box stores, in 11 oz. tubes.

The spans may be to long for that width of joist.
Very likly to crack the plaster below.
http://www.awc.org/calculators/span/calc/timbercalcstyle.asp?species=Eastern+White+Pine&siz e=2x6&grade=No.+2&member=Floor+Joists&deflectionli mit=L%2F360&spacing=16&wet=No&incised=No&liveload= 40&snowload=-1&deadload=10&submit=Calculate+Maximum+Horizontal+ Span

Thanks, Joe. That is very interesting, want to see how it computes for the distances from the load bearing walls. I wonder if there are ways to reinforce the joists or other ways to stiffen the floor.