I have a walk out basement with two small windows near the ceiling. these windows are about 2 feet wide and maybe 1 foot tall. I’d like to take out this window and put in a more standard size, to get more light into the basement, say 2 wide (no wider than the original window in there) and 3 feet tall. The wall is concrete block. Does anyone know if I can simply take the old window out, cut the block the size I want and install the new window? My concern is about some kind of header above the existing window. I would like to think that the header will accommodate the window below it, regardless of how tall the window is. Is this correct?

As long as you do not disturb the supporting portion of the wall under the existing header you should be able to increase the height of the window without a problem. Just be careful when you are cutting the blocks that you do not break out the sides and leave the header unsupported.

For $50 I rented a circular saw built for the purpose of cutting concrete or brick and it took me maybe twenty effortless minutes to slice a wider doorway opening through our front brick wall. While it doesn’t apply to your situation, it cost me another $100 to have a welder extend the supporting steel lintel (header). I’ve seen brick/concrete-cutting done several other ways, but all involved more work and/or money, and none resulted in the fine finish the saw gave me.

My follow up question is this… It appears that the floor joists are sitting on a 2xsomething, and the 2xsomething is immediately above the window. Is this 2xsomething considered my header? there is no additional 2xanything above the window. And this 2xsomething continues maybe 4 or 5 feet beyond the window on the right side, maybe only 6 inches on the left side.