Installation of exterior and interior window sills

The best way of installing the window boards is to fit them together with the window frame - PVC, aluminum or wooden.

The window sill is placed in the clear opening of the window, then the window itself is installed on the sill, it is levelled and fastened to the wall with wall plugs together with the window board.

reveals, however, that this way of installation is not always applied; therefore we demonstrate the following alternative methods of installation of window boards in the cases of already installed new windows or when old and functional windows are to be remade and given a new aesthetic look.

Depending on the circumstances and supporting function the three listed methods of installation are possible: gluing, bracket screwing and direct fitting on the masonry with wall plugs.

The distance in front of the window is measured, and you must take into consideration the diagonals of the spot. Cutting is easiest to do with an angle grinder, which must have a larger diameter of the working part (e.g. 180 or 230mm disc) to be more comfortable to use. You can use a circular saw blade for straighter cuts but when the opening is irregularly shaped and requires precise cuts, you must use a jigsaw with a longer blade.



USING ADHESIVE – when we have a sufficient working width with no danger of detaching in the event of pressure on the edge.

kind of silicone is used for that purpose with very good adhesive indicators or professional fixing paste in a proper packaging for installing with a silicone gun.

The adhesive mixture is applied with the gun on the spot, on which the board is to be fitted, in a zig zag pattern in a thicker layer so that after the board is fixed and pressed on, the material can spread everywhere.

Depending on the position, the caps can be fixed beforehand (with some silicone) on the board or to be glued afterwards.

The gap between the window sill and the window can be filled with a thin layer of silicone in a suitable color.

ON THE MASONRY with wall plugs to fasten the board.

This type of installation is used when there is limited area to support the board in front of the window, i.e. when we have a board that extends beyond the edge of the wall and there is less space for fixing.

Dry water based construction adhesives are used here, which only seal the space under the board, while the fixing is done with wall plugs through the board itself onto the masonry.

Holes of Ø5-Ø6 mm are drilled (with a drill) at the spots for fixing with a larger hole on the top face side of the board, so that the drill bit head can go through.

After preparing the adhesive mixture, apply it on the masonry with a suitable tool, place the board cut to size (and drilled) and fix it with the help of weights to prevent it from falling.

After the mixture dries, while supporting the board, drill holes in the wall through the openings, put the wall plugs and the right size screws and then cover the openings on the upperside of the board with decorative caps of similar color.


Fixing with brackets is recommended when there is zero or little space to attach the board. You must work with precision in order to have a good result. The caps of the window board in this case are fitted in the beginning (with adhesive). The board is then fixed and the number and type of angle plates to be used is determined. They are screwed to the underside of the board with shorter but thicker screws, and to the wall with fasteners suitable for the type of wall (concrete, brick, drywall, etc). The gap between the window board and the window can also be covered with a layer of silicone in a suitable color.

You can see the exterior and interior window sill models here >>