Remodeling Attic Space

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averagejoemn

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Greetings!, my wife and I are about to start our first major home IMPROVEMENT project (all the other projects have been REPAIR).

For background; we have a 1929 story and a half Tudor home in Minneapolis. The half story is almost completely finished except for a 11'x10' space off of the master bedroom that was never finished. The current floor in there is 2x10" boards running the wide way, the insulation below it is vermiculite so I covered the floor with rosin paper to keep dust down.

Our plan is to finish this space and use it as a walk in closet. I have paid for a permit to begin construction. I have a decent amount of tools for the project and have intermediate wood working skills. The complexity of this project is around a couple issues, mainly ventilation and how one side of this space is shaped.

My plan in this order:
I plan on nailing down some 3/4" plywood over the floor we plan on using (not then entire floor)

Construct a knee wall:
Nail down a 2x4 bottom plate for the knee walls on each side.
Nail a 2x4 to the existing rafters to allow for a 4ft knee wall
Miter cut the support 2x4s to join the bottom plate with the knee wall top

Measure where the ceiling height should be and cut 2x4s to connect the rafters (should these be mitered to fit between the rafters? or just nail them to the sides? doesn't matter?).

Join the knee wall to the new ceiling 2x4s.

Have contractor install a few outlets and overhead light.

Insulate, moisture barrier and drywall.

Have contractor mud and tape.

Install overhead light fixture.

Install floating bamboo flooring.

Build in some storage TBD.

Does my general plan sound correct? Does the order look good?
What size nails do I need to use for framing and also securing the plywood to the floor?
Is 3/4'" plywood the correct subfloor? Should I go thinner?

Here are some photos and plans of the house:
atticspacephotoKneeWall.jpg


atticphotofacingback.jpg


atticphotooppside.jpg


peakphoto.jpg
 
There should be vents that allow air to enter at the soffets and escape at or near the peak of the roof. As you only have 2x4 rafters, this will not allow air flow and insulation so I would make them deeper in the area from you neel wall to the ceiling. 2x8s would allow 6" insulation and air flow above that. The outside wall with the window I would also make that into a 2x6 wall for more insultion. The insultion around the older structure should be held inplace with strips of wood or something, not plastic.
 
Thanks nealt, any thoughts on nail size to use? Frame on top of the plywood or not?
 
Three inch nails for all the framing and I would put the floor down first, if that was the question. And I would build the pony walls out of 2x6 for more insulation.
 
Neil's points are correct. I always build my knee walls on the flat floor, then stand them up and secure to the rafters. I guess you could build it in place and secure to the sides of the new 2x8 rafters. But you want to make sure you snap a straight line so your walls don't wave in and out.

If your sub floor is sound you might get by with 1/2" plywood. This is just a closet so there is very limited dead weight on it.

Dave
 
And don't waste the scuttle-space behind the knee walls, either. A few small access doors in each will allow storage for small, seldom-used items. Or even a place to stuff the kids when they get mouthy--with enough insulation, you shouldn't even hear them screaming from downstairs.
 
And don't waste the scuttle-space behind the knee walls, either. A few small access doors in each will allow storage for small, seldom-used items. Or even a place to stuff the kids when they get mouthy--with enough insulation, you shouldn't even hear them screaming from downstairs.
Definitely, except that kids may be frequently used items. Don't go there. :eek:
 
Building a nee wall straight and level with a straight transition line to the slope is tricky to say the least. I build the wall on the floor and stand it up and set it on a straight already on the floor. I build it to fit under the lowest rafter. I hold the top in place by adding 2x4 blocks from beside a studs to the rafters behind locking it in place level and straight. The top plate is the required firestop. Add the another 2x4 to the rafter directly above the wall with a level in hand, this should be straight. The side of the 2x4 can be cut on the angle to make it easier for inexperienced drywallers.
There should be 2x4 blocks on the flat between the rafters for the ceiling drywall to be screwed to, so it dosn't sag.
 
Thanks for all the feedback, we have everything framed out and electrical rough in is complete. Tomorrow morning we have the electrical inspection followed by the framing inspection.

We did not add firing strips to the existing rafters for the additional thickness. I spoke with a contractor and he said to put 1.5" rigid insulation between the rafters and then 2" rigid insulation on top of that followed by a moisture barrier and 5/8" drywall. Behind the 1.5" insulation will be a void of 1" to allow airflow from the soffit in the floor out through the vents on the roof. Any thoughts on that? I'm assuming if that's incorrect the inspector will tell me.
 
Just passed our electrical and framing, onto insulating. I'll try to put up some new photos.
 
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