Converting Sleep sofa to sofa using plywood as seat foundation

[Boyblue]

I would like to convert some sleep sofas into regular sofas by removing the bed mechanism and framing inside the perimeter with 2 x 3. I'm thinking 1 x 3 doesn't have enough girth and those are the only options available to me. Should I use one or two members front to back? The plan is to deck with 1/4" or 3/8" plywood, covered with batting and then lining. My upholstery guy says the thicker the plywood or the more firm the foundation, the quicker the cushions will wear out. Is 1/4" plywood sturdy enough? The opening is 36" x 68"

 

[Dj2]

1/4" plywood is not sufficient for a sofa base.
Use 1/2" plywood over 2x3 - 16" on center.

 

[Sponsor]

 

[Boyblue]

1/4" plywood is not sufficient for a sofa base.
Use 1/2" plywood over 2x3 - 16" on center.

I'm sure you're right about the 1/4" but I stopped by another upholsterer this morning (he owes me some work so he didn't mind sharing his trade secret) and he is suggesting I use 3/8" and frame the perimeter with 1 x 3" - no cross members necessary. I realize that furniture construction is different but I can't imagine not putting in one or probably two cross members.

His thing is the plywood and 1 x 3 will be anchored by the many staples used to attach the 1 x 3 to the inside of the sofa. I like the idea of cross members not necessarily for support but to prevent spreading but if the plywood is nailed off properly spreading should not be an issue.

 

[Dj2]

Upholsterers are more interested in their bottom line, which means skimping on lumber.

1/4" is too thin.
3/8" is too thin, unless you have lots of cross lumber.
If I'm not mistaken, 1x3 is more expensive than 2x3.
That's why I think that skimping is foolish, when you are building your own sofa.

 

[Boyblue]

I'm turning a regular sofa into a sleep sofa. The upholsterer I spoke with suggested a plywood thickness that would have some give because he explained the the cushions would ware out quickly otherwise. He suggested 1/4" but I'm afraid that's too thin, so "I'm thinking 3/8" would be a good compromise.