Logistically, the designer's drawing makes more sense.

-Entry from a common area vs. through the laundry (do you really want everyone going up to the bonus room to see your laundry room?)

-Stairs run parallel to the ceiling joists vs. running perpendicular to them.

-Plenty of headroom clearance as you go up the stairs. It looks like you have a 10/12 pitch on the garage roof. That means for every foot of run (from outer edge of roof line moving toward the center of the roof line) the roof rises 10". Given a 18" overhang & 6" exterior wall that means the roof across the width of your proposed staircase as drawn on the post only rises to ~20-40" from the lower edge of the exterior roofline. When you're standing on the top step, that's all the vertical space there is--20" floor to ceiling closest to the garage wall-40" floor to ceiling at the outside edge of the staircase. In the designer's version the roofline goes up at approximately the same rate as the stairs so you're good to go there.

-Your bonus room size is maximized. Running the stairs parallel to the rafters allows a 5' knee wall on either side giving you a space 20.5' x 24'. The side walls will be short--only 5' tall but will get taller as you move toward the center of the room. To get to an 8' knee wall to allow adequate headroom at the top of the stairs like you will need in your layout, your room size shrinks to 10.3" x 27.5". Here's a visual for you...

Your Layout

Designer's Layout

Not what you wanted to hear, but I hope it helps!

Is there a reason the designer didn't stack the stair cases? I am not sure why they need to be side-by-side.

Thanks everyone for the responses! This helps me tremendously!!! I see now why I'm not the architect:)

I may ask about stacking the staircase though.

I think the architect didn't stack them because you have only one end to enter from whether going up or down if you do a straight run staircase. However, you could do a 'U' shaped staircase that would allow you to stack them, entry to either staircase from the same side and would shorten the total length of the stair a bit which would mean you could add a little more room to the bathroom at the end of the hall or add a closet.

Since the layout calls for entering the stairs at opposite ends, putting one on top of the other works fine and saves quite a bit of space even compared to a U-shaped stair. It might require more offsets/corners in the foundation wall or modifications to the first floor plan but it would be worth it.

Renovator8--I know the arrow for the basement steps shows them going in the opposite direction from the bonus room steps, but that leaves accessing the basement steps through a bathroom. I wouldn't think this would be the best place to access the basement stairs. It would also explain why the designer didn't stack them and set them side by side instead.

I don't see why they'd need to be accessed from the bathroom. There could be a door from the hallway; or just open from the hallway... Stacking should be considered.

Stacking is when the unused space under an "up" stair (going to the bonus room) is used for a "down" stair (going to the basement). They are similar in design but one is one floor higher than the other so headroom is maintained. Where they can start depends on the ceiling height.

The stair to the basement would be entered from the hall. I believe there was an earlier version showing this arrangement. It is very helpful to others when stairs and doors are shown on the drawing. Incomplete drawings will be interpreted differently by different people and that can derail the design process.

Here is a section cut through two stairways. From the middle floor, one goes up and one goes down. On the plan they occupy the same space but there would be be a diagonal "cut line" in the center of the length of the stair so that only the first half of each stair is shown.

Thanks for all the input.

The drafter came back and stacked the staircases using the top run.

However, my bonus is only 13' which doesn't seem wide enough. It seems like with a 27' wide garage my bonus could be bigger. She has something like a 7' knee wall on either side.

I haven't spoke with her as my husband just picked the blueprints up. She hand draws everything so I'm trying to reproduce in Chief Architect as best I can and would love your expertise on why my bonus is so narrow?

THANKS!

If you look at your front elevation (which is very pretty BTW) you'll see why the bonus room is so much narrower than the garage: with the slope of the roof above the bonus room, there is no headroom for several feet on either side. You can still make that usable space by building storage into the side walls like low drawers or shelves, closets (with low, sloped ceilings), or an alcove for a mini fridge or TV if you don't mind that it's low, or even trundle beds that roll away when not in use.

The link shows some ideas.

Here is a link that might be useful: making the most of attic space

Thanks, chicagoans!

What could make the bonus wider...a different pitch?

Shorter knee walls would also make it wider. My upstairs is "under eaves" of a cape cod style house. My knee walls are 5'. If you have a 12/12 pitch roof (not sure what yours is), making 5' knee walls would take your room 4' wider (to 17').

Go onto Hulu.com and watch an episode or 2 of wasted spaces to see how they regularly make use of "wasted space" behind knee walls of steep pitched roofs.

kberrie,

I'm not an architect so you'd have to ask yours for the best approach to getting more floorspace up there. I believe there are a couple of approaches... and any of these will likely add to the cost and change the look of the house (possibly making the garage/bonus area more dominent than you'd like.)

Here's a very rough mockup. Left to right:
Blue is the approximate shape of the current plan. Dotted line shows the approximate width of the space with adequate headroom (based roughly on the height of the front door.)

Green is if you just changed the pitch of that roof. You'd have to go high and steep to significantly change the width of the usable floorspace, making that roof higher than the main part of the house. Not only might this be odd looking, it might be very cost prohibitive to build a roof that high/steep.

Purple is if you built short vertical walls for the bonus room and kept the center of the roof roughly the same height. Naturally this makes the roof pitch flatter. Don't know if that shallow pitch is recommended/allowed or not.

Grey is if you added short walls and made the center line of the roof a bit higher, but not as high as the green option. Naturally the higher you make the side walls, the more usable floor space you have (and the higher your roof is and/or it will be flatter.)

{{gwi:1424434}}

Hopefully this shows a bit how changing the roof pitch and wall height (from zero to whatever) changes that floor space. Your architect can tell you what, if any of this, is allowed. But I thought I'd put this out here to give a sense of how the floor space gets to the size it is.

I think you'll have to consider the cost and the impact on the look of the house compared to how much you value more space up there.
HTH

The one that is left out above is what I mentioned. Take that blue diagram, and move the right and left walls out to the the sides. Then, you will have some space that is under an angled ceiling (which you have in your current plan, since you have "knee walls"). Instead of 7' knee walls, they would be 5' high, meaning your angled ceiling would come down further out and further down than it would with the current layout.

What that means, is that you would not be able to stand up straight right at the wall (unless you are only 5' tall); But, rarely does one need to stand up straight AT a wall. Usually, you are a foot or 2 away. (I am 6' and haven't hit my head in my master bedroom, which has this sort of configuration).

My pitch is 10/12.

Thanks for all the insight!