How to measure windows for new construction?

pastrami

Hey guys, first post, so hopefully, this is the right place to ask this. I’m planning on replacing my old windows with some new dual pane windows. I understand there are two types, retrofit and new construction? I’m going to go the new construction route, but I’m confused as to what to measure and what numbers to use for ordering. I’ve read a number of places regarding rough opening, and how much to add, etc but I’m confused, hopefully someone can shed some light into this.

The windows I have are the Aluminum casement windows.
Do I measure from the inside or the outside? A coworker suggested that I measure from the outside.
If I measure from the outside, do I take the measurement from one end of the frame to the other end of the frame?

Are those the numbers that I will use to order the windows or do I have to add an extra 1.5in to it? I’m not home but I can take some pictures if that’ll help. And would I require to get the nail fins for the windows, my coworker said I didn’t.

Thanks in adv!

AtlanticWBConst.

Honestly, the most accurate way to measure for new construction windows and have an exact fit, with no issues and minimal additional work, is to remove the interior vertical casing on one side of each window (that is a different size from others).

By doing this, you will be able to see exactly how much space is between the exisiting window jamb and the rough framing. This will give you a 'gauge' as to where the framing is on the opposite window jamb, without having to remove it.

You will also be able to see the bottom rough framing and the upper rough framing (Header).

The distance of the rough framing edges - is the measurement you will use when odering your windows. If it is close to a fractional measurement, always go with the 'smaller' measurement.

Thus you will have your height and width rough openings.

When done, just re-install the casing....

(I prefer to get these exact. Not that it is the end of the world if you are off, it means that you have created ALOT more work for your installation process. The last thing you ever want to do is have to rip out headers and change the framing layouts....because that means you will be doing alot of drywall work, along with alot of siding and exterior trim work as well...)

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