ᐅ Installation of Granite Window Sills: What Is the Best Method?

Hello dear forum members,


I’m interested in how your natural stone window sills (for example, granite) were installed when you have an external thermal insulation composite system (ETICS) using EPS on your house.

One stonemason says you have to use brackets, while another says mounting foam and some mortar are sufficient. I have an appointment with a third stonemason, but I’m already quite confused.

I found a guideline for stonemasons that also recommends the bracket method.

Do you have long-term experience regarding the technical reliability?
I would like to avoid the window sill simply resting on the EPS insulation, which might give way over time.


Best regards

Expanding foam and silicone are always helpful :-p.

But seriously. I’m not an expert, but if someone suggests using expanding foam outdoors where it is constantly exposed to the weather, I would probably send them home right away.

Expanding foam neither seals properly nor is weather-resistant, and it crumbles over time.

Aliban2014 schrieb:
Would like to avoid placing the windowsill directly on the EPS insulation, which might eventually give way.

Then you have basically found the answer yourself:

Aliban2014 schrieb:
I found a guideline for stonemasons that also specifies the use of consoles/brackets.

Never, absolutely never (as they say in Bavaria) can something glued on serve as a proper support for a heavy load. Even poor workmanship holds up—until the warranty runs out. The smart choice is to follow the correct installation method. Whether you really recognize the devil in the details, I don’t know—but the botched job on the construction foam is obvious.

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11ant schrieb:
Then you’ve already found the answer:
Never ever (as they say in Bavaria) can something glued on serve as a proper support for something heavy. Even shoddy work holds up—until the warranty expires. The smart choice is the professional method of installation. Whether you can truly recognize the devil in the details, I don’t know—but you can definitely spot poor work from spray foam.

Very great post :-)))



Thank you all for your answers, I will probably have it installed with brackets then.