Large cushion

[Joys Shop]

I've always had a problem with large cushions

with a normal size cushion I add 1/2" around, and 1" in depth
with a 3" cushion, 23 X 23
I cut 4" foam 24 X 24
but
I have to make a cushion that is 48 X 52 X 3

Do I follow the same procedure as for a small cushion?
or
do I cut the foam the same as the finished size of the cushion (and maybe add dacron to top and bottom)?

I hadn't discussed buttons with the customer, but if I have to add them, I believe they would be alright with it

[bobbin]

I add 3/8-1/2" seam allowance to the top and bottom pcs.  I would cut the boxing for 3" foam at 3 1/2- 3 5/8".  I take a 1/2" seam allowance when joining pcs.  For the foam I add a solid 1/2" to the finished perimeter dimensions, and that depends on the density and quality of the foam. 

I find my recipe allows the boxing to pull the top and bottom nicely over the cut edge of the foam.  If you don't like the "look" you can add batting to fluff up the top/bottom or you can give the foam a haircut. 

That sucker ain't gonna be any fat lady's dream to stuff!  Eat your Wheaties.  :)

[MinUph]

Joy,
  On larger cushions I don't keep with the 1" oversize on the foam. I will cut the foam 1/4" larger than the finished size and wrap it with dacron, if it wont lay flat I cut the 1/4 off. Whenever you have a long cushion the foam doesn't lay as well as say a 24" cushion does. It will tend to buckle because there is just to much foam to stretch itself out like the smaller example. If it is real long I will make it the finish size of the cushion so it basicly just finds its own place letting the dacron take up any excess.
  Sometimes it seems like trial and error in this business even after 43 years :)

[Joys Shop]

thanks

If I decide I cut it too small, I can always add back to it

[kodydog]

I'd rather err on the to big side. Personally I think its easier to cut foam down then adding some to it.

[Joys Shop]

but if you use 4" foam when it should have been 3", that can't be cut down
but
if you use 3" when it should have been 4", you can glue a 1" piece to the top

[sofadoc]

but if you use 4" foam when it should have been 3", that can't be cut down

That's true if you don't have any way to slice foam horizontally. You probably should use the "add a layer" method.

Every time this question comes up, it seems that we all have a different method. If I'm making a 3" cushion, I use 3" foam and top it off (or wrap it) with batting. I cut my boxing 3.5".

[Mike]

for marine cushions 2" foam I cut 2.25 " boxing with a 3/8"vallowance if its smoothe vinyl I lglue a 1/4" layer of foam to the vinyl to give it body

[Darren Henry]

I use the same method as 'Doc. My boxing finishes 1/2" less than the foam, and my foam is 1" wider and longer. If there is any stretch at all in the fabric/vinyl I would not cut to the finished dimensions. As Kody pointed out it's easier to trim than add, although I seldom have to do that even on large cushions like these.

[baileyuph]

The general analytics I use are about what all have said (spot on with Bobbin's strategy). 

One point however, Joy I never use 1 inch thicker foam than the prepared cover.  But, I understand that one might use that approach on foam thickness if the density of the foam is very soft.  Most time my foam is not that light weight.

For the variances that come up on longer cushions and bay windows, I stick close to sewing the height of the cover to about 3/8 th's or 1/2 inch less than the foam.  Now, the length of the sides is more subjective mainly due to foam density.  On weaker foams, if it is determined or thought that the corners will not look filled then I might cut the foam overall just a little bigger (sides that is).  Going longer on the foam sides will fill corners better, when the foam is softer and it will not likely bow the cushions like a higher density foam will.

Seems we all are close but reserve rights to variances as the situation dictates.

Good luck,

Doyle