span / sag question for a window seat

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Forum topic by jimmy J posted 02-19-2014 08:23 PM 1014 views 0 times favorited 10 replies Add to Favorites Watch
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jimmy J

229 posts in 2378 days

02-19-2014 08:23 PM

I’m planning a window seat for my son’s room with two rows of two drawers underneath. the total height is only 21” including toe kick, so the spacing below, between and above the inset drawers is fairly small – 0.75”. the design calls for no separate piece above the strecher – the 0.75” upper stretcher would extend from the front face back to the wall, acting as a top. a cushion goes on top of this piece.

the span of each drawer is 32” wide and 20” deep. The Sagulator suggest a 1/8 deflection. my concern is the sag when someone sits on the top, and having the top/stretcher bend down and hit the inset drawer front, which would have a margin around it of about 1/8 also. My first thought was to put a support piece under the stretcher, but that would reduce the effective height of the drawer.

Any creative suggestions on how to reduce this sag?

10 replies so far

View AandCstyle's profile


3052 posts in 2256 days

#1 posted 02-20-2014 02:04 AM

I am not certain that I totally understand what you are describing, but that never stopped me before. :D How about mounting a piece of 1/8”x 1/2” angle iron to support the back. There will be no sag with that in place. HTH

-- Art

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18271 posts in 3675 days

#2 posted 02-20-2014 02:28 AM

Do not forget to kid proof it. If he doesn’t jump on it, his friends will ;-)

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View RogerInColorado's profile


321 posts in 1954 days

#3 posted 02-20-2014 02:49 AM

I’d probably run thicker stock through the sagulator if I was concerned about deflection. Nothing wrong with 5/4 or 6/4 or even 8/4 seat thickness.

View bondogaposis's profile


4727 posts in 2350 days

#4 posted 02-20-2014 03:17 AM

I’m having a hard time visualizing this. A picture would help immensely. What is the total span? An 1/8” deflection is way too much. Beef up the the seat to at least 6/4 stock. Kids are going to be jumping on this.

-- Bondo Gaposis

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294 posts in 1660 days

#5 posted 02-20-2014 03:23 AM

kids teach us lessons we dont need to learn

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jimmy J

229 posts in 2378 days

#6 posted 02-25-2014 11:56 PM

Thanks everyone. angle iron suggestions is what i intend to do. since my top will be made of 3/4 and 1/2 ply glued up, i was able to find some 3/4 angle iron that slots right in to the lower layer. will let you know how it goes.

View firefighterontheside's profile (online now)


18187 posts in 1856 days

#7 posted 02-26-2014 02:44 AM

Is this going to be built in? I would think the best way to get strength would be to have a rail and stile face frame that would give strength across the span of the drawers.

-- Bill M. "People change, walnut doesn't" by Gene.

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jimmy J

229 posts in 2378 days

#8 posted 03-02-2014 03:48 PM

Bill, yes, it is going to be a built in/have a face frame. that does not seem to make much of a difference in the Sagulator analysis. The back edge of the builtin against the wall will also be pinned, which will help reduce the sag. sag will be zero in the back due to this, but not sure how much it will help at the front face.

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11626 posts in 2379 days

#9 posted 03-02-2014 05:03 PM

I can get see it’s going to be at least a 64” span, presumably with a frame front and back, and one between the drawers (if not, there should be) which will reduce your span by half. Other than that there isn’t enough information for anyone to answer except to guess.

-- Rick M,

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jimmy J

229 posts in 2378 days

#10 posted 03-17-2014 08:07 PM

FYI – this is the result. The top of the seat is upside down here, and the face frame will be applied to the left side of this. Its only 1.25” thick, but the deflection is almost zero.

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