Measure for Window Replacements

[CooSer]

My 48 year old house has the original windows. They are double hung with aluminum tracking. I want to start replacing these windows one at a time as I get the time and money. I am nervous to measure for a new window because I am not sure what to measure. Do I need to take the old window and track work out to measure the inside of the frame? Do I just measure a panel? Or is there a better sure fire method to do this? Any help would be much appreciated. Thanks.

[Edwin Pawlowski]

I can't see your windows but most are fairly common double hung sashes riding inside a casing. You remove the stops to take out the sashes. You want to measure the distance between the place the sash slides on, the same dimension as where the stop sits now. Measure the height from the inside of the sill to the top.

To be sure, ask the guy at the window store because his brand may differ slightly. The windows I used to install had a header on top that expanded to take up a gap of up to 1".

[CooSer]

Well I can't really ask the guy at the window store because I am waiting for returns at the hardware store. Once my size comes in I hope to get a good discount.

Are you suggesting that I take the old window out, or just take the molding off that keeps the window (sash?) held in?

[Edwin Pawlowski]

There are many types of windows. I used to sell and install "replacement" windows that sat inside of the existing casing. The sash was removed by taking off the bead around it (inside the casing) and then putting caulk on the stop, sit the new replacement into the casing. Screw it in place, replace the bead. This was most often older homes with painted windows in a brick wall. It took less than 30 minutes a unit, looked like the original from the street, had all the advantages of modern technology, tilt for cleaning, etc.

If you are taking out existing widows with a nailer under the siding, that is a different story. Different fit, different mounting.