how do you find square footage for drywall from square footage of floor area?

Question

need to know is it different from 8ft. to 10ft. wall height

Answer 1

You don't find the answer that way. Builders may use it for approximation, but they know what extras to allow for.

Floor area does not take into account the spaces for windows and doors, the height of the walls nor the fitting of the material
For the D-I-Yer fitting can be a serious variable.

Measure the room and write down all the numbers.

Height is VERY important.

Drywall can be installed horizontally, according to the centres of your studs, or it can be installed vertically, in the same manner.

Bear in mind that you WILL have scrap/leftover material.

Houses built today are done quickly and there are almost no truly careful builders. You are virtually guaranteed to find you have walls that are not plumb and corners that are not square.

Trimming is inevitable.

Drywall comes in standard 4 foot widths. 8 and 12 foot lengths are common, but 10 and even16 foot lengths may be available, depending on the suppliers where you are.

If you were to have a nine-foot wall height then you would have to deal with either adding and extra section above 8 feet or you would have to use a longer piece and trim it to fit. This would be faster and would produce a better result as it would mean one less seam for you to fill in and the one-foot section would remain more flexible than desired and would encourage pop-outs at a later date. Pop-outs are screw or nail heads that back off and appear on the surface due to, humidity, flexing of the material or both.

The left-over drywall parts could be used elsewhere, such as behind cupboards or over windows, or they would be scrap.

Answer 2

Shannon,
With drywall, you are trying to enclose either 4 or 5 sides of a box (walls = 4 sides, ceiling = 5th). If it's a rectangle then the square footage is the length of each side times the height and add the 4 together. Then length times width for the ceiling and add. You also need to leave some allowance for cutting waste.

A professional drywall installer may be able to give you a gross estimate based on square footage of the floor area.

My estimate would be this: Assume sq footage = 900, then the room is 30 ft by 30 ft. Assume 8 ft cieling. Exterior walls = 30*8*4=960 sqft. Cieling = 900 sqft. So, at the minimum it is double the sqft. But now look at it, that's a 30 by 30 room with no interior walls, no closets, no bathrooms etc. If we divided the room into 4, 15 x 15 rooms then we add 1, 30 ft wall lengthwise and 1, 30 ft wall across with sheetrock on both sides. That's another 960 sqft.

So, that's 2820 sq ft. I would estimate 10% waste, which brings us to 3100 sq ft for a 900 sq ft floor area. The ratio is:
3100/900 = 3.44 times the floor area.

If I was buying sheetrock to do my basement (or a whole house), I would take the floor area and multiply by 3.5 That should leave about a 10% waste factor.

This is just my educated guess.