Sewing question on kids clothes, not quilting
 

My grandson has a problem that every brand and size of pants his mom buys him is like they are not long enough in the back and his butt crack shows. He has a chunky but but it seems like he is just long in that area and none come up far enough.
Does anyone that sews or have kids with this problem have any ideas on alterations or ways to fix this?

Just wondering his age and the size pants? Toddler pants have extra room for a diaper which in most cases is enough to avoid the problem. But if he is out of diapers that isn't the issue and maybe look for different brands or cuts of pants. For example avoid low rise. Let us know how it turns out.

I think a huge problem is pants are made low rise nowadays which makes it hard to find pants that cover the butt generously

It is possible to alter the crotch seam. If you took in the seam from the center front to the center back, it would lengthen the crotch. If the front crotch length is ok, and it was just the back that was the issue, don't take in much of the front seam, just take in the back and blend into the front.

Buy the pants LONG, because this alteration will shorten the leg length a bit. It will also cause you to loose a bit of the hip width.

To shorten a too-long crotch, you would alter the crotch from leg inseam to leg inseam... but that alteration will narrow the legs of the pants somewhat... and lengthen the legs.

If the butt area is a bit baggy you could alter the depth of the crotch seam, as in this diagram, but that will make the legs shorter and tighten the pants across the backside and the front, so I would try with inexpensive garments first.
[ATTACH=CONFIG]582579[/ATTACH]

How old is your grandson?

If you look at him from the side, is his natural waistline parallel to the floor - or does it slope down in front?

This calls for an alterstion not found in many alteration books.

Backsides come as "flat, average, and rounded" - lok at the alterations for "full derriere" to get some more fabric in the area.

You might need to change brands to find a style that fits him better.

Boys sizes come in "husky" which should give him more fabric in that area but could cause too much fabric in other areas. But, better to take in than let out as they don't make them with any extra seam allowance. On men's sizes, he would have to try big/tall sizes.

Oh i have a two yr old Great Grandson who may end up with this problem. He is soooo heavy to pick up now.

It's important to know his age and the type of pants you are talking about in order to answer the question. Are we talking jeans of pull on types?

if you are sewing him pants, you can lenghten the pants across the bum area above the crotch curve to lenghten the area. If they pull down because are tight across the bum, add fabric to the entire middle seam , curving into the point where the leg actually starts.

If you are altering them (and with jeans I would just buy a more generous cut) buy larger and then take it at the side seams if too big.