ᐅ Compensating for insufficient parapet height using rigid foam insulation boards

A friendly "hello!" to everyone!

We are currently in the shell construction phase. The building is using a Wienerberger Plan T-10 block. The window openings are mostly finished. According to the plans, the sill height should be 104.5 cm (41 inches) above the top of the foundation slab. The masonry has been built up to about 101 cm (40 inches), which corresponds to four courses of the Plan T-10 block. So, about 3 cm (1 inch) are still missing to reach the desired sill height. Our site manager suggested compensating for the missing height with a 20 mm (0.8 inch) Styrodur board.

My question is whether this is technically sound and if the Styrodur board might compress once the windowsill is installed and subjected to load (for example, if someone leans on it). If the board compresses, I am concerned that the windowsill could crack or break.

Am I just overthinking this, or is my concern justified?

Good luck

Styrodur is a rigid, compressive-resistant foam that does not handle point loads well. It is used in sandwich constructions, for example, in surfboards. I think it can be done. Karsten

Okay, thank you. One less thing to worry about.

joegamble schrieb:
According to the drawing, the parapet height from finished floor level is supposed to be 104.5 cm (41 inches). The masonry was built up to about 101 cm (40 inches), which is four courses based on plan T-10. So the target parapet height is still about 3 cm (1 inch) short.

Which "specialist" designs such heights? Could it be that you measured incorrectly, meaning the screed or flooring build-up wasn’t taken into account?

I imagine that another layer of smaller format bricks will be added (a standard brick would add about 6.5 cm (2.6 inches), a modular brick about 8.5 cm (3.3 inches), and a double modular brick about 12.5 cm (4.9 inches)) and, by recalculating the floor construction, everything will match up again. No sensible planner sets parapet heights in arbitrary dimensions that don’t correspond to brick formats. But it would be normal to build the large-format bricks first and add the smaller format bricks later.

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Well, it seems that we ended up being the "specialists." We requested a parapet height from the top edge of the finished floor to the top edge of the window sill of 87.5cm (34.4 inches). The architect adopted this as well. The 104.5cm (41.1 inches) height from the finished floor level is made up as follows: 20cm (7.9 inches) floor buildup + parapet height from the top edge of the finished floor 87.5cm (34.4 inches) = 107.5cm (42.3 inches) - 3cm (1.2 inches) window sill = 104.5cm (41.1 inches).

joegamble schrieb:
20cm (8 inches) floor construction + parapet height top edge of finished floor 87.5cm (34.5 inches) = 107.5cm (42.3 inches) - 3cm (1.2 inches) windowsill = 104.5cm (41.1 inches)

???

Parapet height is usually measured at the bottom edge of the windowsill... so 20cm (8 inches) floor construction plus 87.5cm (34.5 inches) equals 107.5cm (42.3 inches).

Are you planning to install a kitchen countertop beneath these windows? What is the ideal working height for kitchen tasks you have determined?