Sometimes even with deep pocket flannel sheets, it is not enough to cover a thick mattress exactly just right. A mattress with added foam can become as thick as 20 inches or more and most deep pocket flannel sheets can only cover up to 14 to 18 inches of mattress. If ever that happens to you, it would be wasteful to throw away good deep pocket flannel sheets just because they wouldn’t fit. Additionally, since these are desperate times, it would uneconomical to buy another new one when the old one still looks like new. With these few alterations that I have tried, you too can make your deep pocket flannel sheets fit your new bed however thick it may be.
Most would think that altering the four corners of the sheet would be enough but sadly, doing so would only produce poor results. If you want the corners to fit snuggly, it would be best to do some simple alterations on the entire sheet. First thing you should do is measure how much extra fabric you would need to add to your old sheet. To get a better measurement use this formula that I learned from Good Housekeeping, (mattress width + (2 x mattress depth)) – sheet width. When you’ve figured that out, buy a strip of matching fabric and color that is about the size you need from your measurement with 1 to 2 inches of allowance. Fold the extra sheet lengthwise and cut along the folded line then pin the fabric onto place and sew them on. Then to extend your border, cut the garter off your sheet and lay it on the mattress so you can determine how much extra cloth you’d need. Save the garter because you can use it to do some estimation on how long your new garter would be. When you get your fabric, it doesn’t need to match your sheet because it will be tucked under the mattress. On all four sides, pin and stitch the additional fabric and trim corners into curves for better fit. Around the border, stitch a ½ inch pocket seam and thread in the garter then close the seam.
When you’re done, you will now have much bigger deep pocket flannel sheets that not only fits perfectly on your mattress but is customized to your needs. You can do this for all your other bed sheets while doing this, to save you from several trips.