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Discussion Starter · #1 ·
I'm working on a project to retro-fit insulation between the ceiling and roof of the finished attic level of a 1920s Center Hall Colonial. This third level attic space is your typical narrow ceiling down the center, with slopes to either side, and short knee walls. The flooring in place is a single layer of tongue and groove (3/4") laid directly over 10" joists.

Almost all of the floor boards stop inside the crawl spaces just behind the knee walls - so those crawl spaces weren't accessible for working with insulation without placing 2' x 4' particle board sheets over the joists - which I did. But in the process, about every 4' I encountered a flooring board or two that extended all the way across the joists to the outside wall where the roof meets the top of the side walls.



In this photo you can see two such instances where those long flooring boards continue to the outside wall (this particular section of crawlspace hasn't yet received its 2'x4' particle board deck). What I'd been doing in the spaces I'd already laid particle board was to cut those extra lengths of floor board away so that I could lay those sheets side by side for a flat continuous surface - because those 3/4" boards are taller than the particle board sheets.

But now I'm wondering if those extended boards actually served some structural function in bracing the top of the walls where the roof framing joins it. Those boards were held in place by 4" or 5" nails that I pried up. Given the length of those nails - and how tight the space is where the floor boards meet the wall and roof - it's almost as if they had to be laid before the roof went on. A good bit of space was required to swing a hammer to pound those nails in. Also fascinating about those boards is that there are very few floor joints in all of the attic space due to how long all of the floor boards are. The first two you see in the photo run for 6' inside the crawl space, then another 5' and 9' respectively to the center of the room and past - with no joints.

So the big question: when I removed those floor boards did I defeat some structural purpose they were performing? I should also add that the roof is the original slate tiles. Do I need to add back something structural in the places I removed the flooring?
 

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Discussion Starter · #4 ·
Possibly acting as Collar Ties during construction?
That's kind of the thing that has me concerned about having already taken most of them out. Since the attic floor joists run parallel with the long sides of the house - and thus the roof (as shown in the above photo), I'm not certain what's now serving the function of tying the front and back walls/roof rafter bottoms together along those long lengths, except at the end walls where there are of course perpendicular structural elements. In the photo here, I will note that there are collar ties at the ceiling level of the space:



Perhaps I'm getting too far afield in the "flooring" sub-discussion and should re-post in "building & construction"?
 

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Discussion Starter · #5 ·

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I would think they provided some type of bracing during construction. Besides, your new sheet goods decking will probably provide as much if not more stiffness than the boards. Nice to see the size and quality of the old lumber in those old buildings.
 
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