Boxed cushion clarification

[snowpea]

Hello everyone!

I have been reading the past posts on boxed cushions but I need a few clarifications.  My cushion will fit on top of a hard box that is 72"x22".  So based on past posts I am guessing that I should cut the foam at 73"x 22.5"x3". 

Where the old posts are not clear is the size of the fabric if I cover the foam with a layer of polyester fill (quilt batting).  My questions are:

1.    Despite the polyester fill would I cut the top and bottom piece of material at 73"x22.5" (including a 1/2 inch seem allowance) ?

2.     For a 3" foam, again covered with polyester fill,  what size do I cut the boxing?

3.     Would I need to change the size of the cut pieces if I cover with vinyl versus woven fabric?

4.     On such a large cushion would buttons help to keep the fabric in place and would it affect the cut material size?

Thank you

[MinUph]

I would cut the fabric 1" over size for top and bottom. 3 1/2" boxing if wrapping with Dacron. Buttons will take out the wrinkles in such a log cushion.
  Vinyl same thing. But vinyl will need either a fabric zipper, fabric bottom, or many breathers in the vinyl zipper.

[Darren Henry]

I never make an adjustment for the dacron. My foam and both plates would be cut 73X23 and the border 3 1/2". Sewn you'd have 72X22X2 1/2".

[fragged8]

hi  
i agree with Darren, don't allow for dacron
and add 1/2 all round to the foam only..

when marking out the covering fabric I make mine the exact same size of the
already over size foam,73x23.  once sewn with 1/2" seam allowance it comes back down
to the right size.

  . you shouldn't need to add dacron unless you need a little filling out
or are going for a more puffy looking cushion.

I only use dacron on boat cushions to puff up the top of the cushion
or to hide dips etc in foam faces.

Rich

[snowpea]

Thanks everyone,
By the way, does pipping serve a purpose other than decoration ?

[lruthb]

I was under the impression that the welt was not only decorative but helped give the seam strength.

If I have a cushion 10 x10 with 3"
I buy 4" foam
I cut 11 x 11 cushion
I cut my box at 4
In other words I increase the overall size by one inch from what I want it to end up being.
Like someone already said the dacron is just a bonus to the puff of the cushion as well as keeping the fabric from walking around the foam.

But what do I know!

[gene]

I look at welt cord (piping to some folks) more as an element of style, rather than decoration.

I've heard folks say that welt cord on furniture seat cushions help the cushions to hold up to wear and tear more than without welt cord. I don't know.

If you sew the welt cord to the panel, then sew on the boxing, you will have two stitches.If you sew the panel, welt cord, and boxing with one stitch, then there is only one stitch. Does it make a difference other than the amount of time it takes to do the sewing? I don't know.

I do furniture upholstery and I always cover the foam, at least the top and bottom, with poly batting. If the customer does not want that poofie look, I split the batting so there is still a thin layer of it on the foam. This keeps some fabric from sticking to the foam, when butts are slid onto and off of, for example. Foam can act like an abrasive on some fabrics also. Rather than guess as to which fabrics will stick or wear out in 5 years instead of 10, I use the batting.

I have done a few window seat cushions where the customer wanted straight lines and very flat cushions. These cushions were decorative and not meant to be sat upon, so I did not use batting.

On the issue of the 72" x 22" hard box:

3" foam, 1/2" seam allowance, and a 1/4" welt cord with a 1/2" lip.

I cut the foam 72" x 22".

I cut my panels 72" x 22".

I cut my boxing and zipper 4" width.

I put poly batting on top and bottom of the foam.

My finished cushion cover is 71" x 21". When I put the foam with the batting in the cushion cover, the foam fills the cover very nicely, length, width, and height.

I am 1/2" short all around the hard box. However, the foam helps to stretch the fabric a bit, and the welt cord adds 1/4", and this fills in the 1/2" short fall very well.

If I am using a micro fiber or some other material with very little stretch or no stretch, I will cut the panels 72 1/2" x 22 1/2".

I do a lot of window seat cushions and I never want them to be too wide that they hang over the edge and I do not want them to be so tight that they wrinkle up because they are being quished by the sides of the window casement.

Gene

PS: We have had discussions on this topic before and there are a number of folks who do it a bit different and what I do is what I have found works best for me and it's also what I read someone else was doing so I got what I do from this forum so if you disagree with me please do a SEARCH for the original person who said they do it this way and then tell them that they are wrong. :-) Thank you.

[Darren Henry]

My personal opinion on welt is also that 90 % of the time it is strictly decorative .

That said there is the other 10% where it servers a practical purpose:
> If your working with really thin material t-braid or foam cord helps minimize the "wave " around the cushion.

>In a semi-attached back or one of those marshmellow arms etc that they sell now, a foam or plastic welt will help maintain the shape since there is no foam ,only teddy bear guts or foam chips inside to fill it out.

>It can close gaps ( I didn't say seal) between coaming pads and the hull on boats , conceal a less than perfectly cut piece of frame/cushion board etc...

[sofadoc]

PS: We have had discussions on this topic before and there are a number of folks who do it a bit different and what I do is what I have found works best for me and it's also what I read someone else was doing so I got what I do from this forum so if you disagree with me please do a SEARCH for the original person who said they do it this way and then tell them that they are wrong. :-) Thank you.

Thers's more than one way to skin a cat, or sew a cushion (who the hell skins cats, anyway?)
Some people cut the panels to size, some cut 1/2" bigger, still others a full 1" bigger. You can always compensate with the foam/batting.