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replace marble in the windows board base

:smileysad: I need to installing some windows marble or stone base and I need what is the best way to do it with out  Brock


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Posted 2011-09-10T03:49:58+0000  by sara1128 sara1128

Hello sara1128,


Thanks for your question and welcome to the community!


When you are getting a new window sill put in, most of the time wood is the typical choice. In your instance, you would like a marble or stone to use as a base.


Luckily, the marble or stone sill base can be installed just like any other style of  sill to make the window look great.


In your question, I'm not sure if you were referring to getting a new marble window sill to be put, so in this post, I will go over removal as well as replacement of your window sill, also known as a stool. Keep in mind that things like availability and space of the area may influence what kind and style of sill/stool would work for you.


A window sill is typically made of two parts, the sill itself and usually a bottom part called the apron. In the diagram below, you can see both parts working under the window...

window sill.JPG


If your needing to get the existing window sill removed altogether, first see how and where the sill and apron is attached, as well as the two vertical casing trims. The first thing to see is to get access to remove the apron just below the sill/stool. You can score/scratch the area where the apron/sill meet by a utility knife, breaking the caulk/paint line. With a small pry bar, you should be able to take off the apron while carefully doing so to ensure minimal damage to the wall. At this point, you can take out any finished nails (if there is any) and can reuse them for the new apron! 


Now you should be able to see the vertical pieces of trim, or casing on both sides of the window. Cut any areas that maybe covered up with paint/caulk lines where they meet other areas of the window/wall. This is ensure that when you pry it out, it will have done little damage to the area too. Make sure to pull any finishing nails outside the casing or jamb out completely. 


Depending on how the window was built or manufactured, you should now have access to removing the stool, or sill of the window. You should be able to pry up the sill with the same small pry bar, IF it is nailed down. If it is actual marble or stone, you would need a chisel and hammer if adhesive was used. If this is the case, then the marble will not be reusable. Any debris left over needs  to be cleaned up, and now you are ready to replace the sill!


To get started, you will first need to measure out the width of the window, or the left to right measurement.


Window sills can be used as a shelf extending out from the depth and a little from the sides of the window. So to measure out  your sill, you will need to measure a little more than the exact depth of the window, which is usually around 1 inch. If you need more 'shelf' depth, you can go a little more. Same holds true for the side measurements.

Measure especially inside the window opening at various places and use the smallest measurement for the proper fit for the sill.


In our stores, we carry a few marble and limestone thresholds that can work great for a natural stone window sill. Below is a picture of a 4" depth one I like.

limestone thresholld.JPG


After getting your sill, you can choose what apron style you prefer. We carry a wide variety in our millworks moulding aisle. Whether you get one in a contemporary style or something ornate, it makes for a nice edge underneath the sill.


WIndow sills are most often cut straight, so you can save on not having to do any mitre cuts. Depending on how the window is set up, you will need to cut into the sides of the stone sill to allow a proper fit. It will look like a "T" shape when you are done.


To install the stone sill firmly to the window bottom, I would recommend using an adhesive rated for marble or stone. Below is a picture of this great product.

liquid nails marble and granite.JPG

After installing the sill, you are now ready to install the apron. Remember that while the sill is extended out  a little more from the window, you usually install the apron at the same depth as the window opening. 


To secure the apron to the wall, you can use finishing nails, adhesive, or whatever small fastener that would work best for you. At this point, any nail holes that are exposed, you can cover up with a wood putty or filler to give a uniform appearance. If it is unfinished, now you have the opportunity to stain it or paint it, using a primer first. 


Lastly, consider sealing the stone sill with a good tile sealer that will protect the sill from any water or staining over the course of it's life. We sell these, as well as our marble and limestone thresholds in our tile aisle in our flooring department. 


And there you have it, a stone window sill that should stand the test of time!


Hope this helps you out,



Posted 2011-09-10T17:54:37+0000  by Joseph_HD_ATL
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