Building Homes or Extensions/window


Hello Bruce--
I'd like to install a 24" round window in a concrete block wall in a house in Florida with a stucco exterior. The house is two storeys, and the window will be on the first floor. There is a continuous concrete tiebeam between the floors, and the top of the window will be about 4 to 6" below the bottom of the tiebeam. Are there any particular engineering concerns to worry about? Does a lintel need to be installed, or is the window small enough that no additional support is required? Are there any special considerations for installation of a round window, as opposed to square or rectangular? Thanks very much for your help!
PS  I saw that you've answered similar questions in the past, which is why I've requested you specifically.  Thanks!

Hi Jennifer, I don't think you should have any structural concerns over that small of opening under a concrete tie beam.  The only tough part, short of cutting the block out, is getting something inside the remaining block around the opening to attach the window to.  For a project like this I would use a 4 1/2" grinder with a diamond cutting blade in it to cut the masonry out.  You could use a bigger concrete cut saw but this small of a circle is hard to cut properly with a big bladed saw.  First of all you need to establish what your actual  rough opening size for the window should be.  If you have the window this shouldn't be too difficult.  Simply measure the diameter and add two inches to if the window has a 24" diameter then your rough opening should be 26" diameter or 13" radius.  Using a long concrete drill bit drill a hole through the block wall exactly in the center of where the window will go.  This will give you a radius point inside and outside the wall.  Use this point to draw your circle inside and out.  Then take your grinder and cut through the block inside and out.  At this point you can take a hammer and carefully begin to knock out the masonry.  You may need to use the grinder here and there to cut some of the block out as you do this task.  Once the opening is cut out of the masonry you should have some open block cells you need to fill with concrete.  Get a couple bags of concrete mix and mix up some concrete and stuff it into the open cells around the window opening. By keeping the concrete fairly stiff it shouldn't be too hard to fill inside the block cells.  After this concrete is hard you can take some 1x4 pressure treated wood and cut it into pieces 7 1/2" long (the width of your block) Using 2 1/4" tapcons (concrete screws) attach the 1x4 to the inside of the opening to "buck" it out.after that you can install the window.  

There are alternate ways to accomplish the same results but the above would be my method.  The only drawback to using the smaller grinder is if there is a concrete filled cell running vertically through the opening if there is a filled cell in the vicinity of the opening you will need to cut through it to remove it and this may require a bigger concrete saw and you may need to cut a piece of rebar inside the filled cell.  I hope this information helps, feel free to write again regarding this or other matters..sincerely Bruce e

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Bruce E. Johnson


I can answer any construction related question in regards to carpentry, concrete, drywall, masonry, structural elements of any type of building, residential or commercial. Interior or exterior.


Custom Commercial and residential buildings. Churches, theaters, schools and auditoriums. Most recently I am working with the Catholic Church on several design build committees. I have a website related to scheduling and project supervision. Although my expertise is more related to multimillion dollar commercial, educational and theatrical projects my generous credentials in residential and remodelling construction make me a viable source of information regarding all forms of building questions.

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