POSTED BY aurita | Jan, 12, 2020 |
, Sash Windowsill Replacement

Old window sills cannot be renewed indefinitely. It’s often better to just replace them with new ones. Their installation should be entrusted to a good specialist who will know how to fit them into the window recess and fix it firmly. We explain how to install a window sill and how to properly fit an interior window sill to your home. Window sill installation: instructions. How to make the window sill stable, i.e. securely and tightly attached. A nice interior window sill attracts attention and completes the interior. Both wooden and marble window sills display a window perfectly. You just have to choose their material for the style and function of the interior. In order for the window sill to be aesthetic and enjoy for many years, proper installation is needed. In fact, setting the window sill is not difficult, you can easily mount it yourself, having the right knowledge.

Removing the old window sill

Removing window sill mounted on the brackets is uncomplicated. It is enough to check whether it is not additionally glued or screwed to the wall (window sills are never attached to the window frame). Removing the window sill, whose ends are embedded in the wall, may be more troublesome. The bottom of the window sill has to be hit several times with a rubber hammer to loosen it, after which it can usually be removed. If this fails, you should forge a gap of nearly 2 inches in the wall (around the window sill), then loosen the window sill by tapping it from below and try to pull it out. Once we are able to loosen it, be careful – preferably two people (window sills can be very heavy!) – remove it from the window recess so as not to damage the window.

After removing the old window sill, check that there are no gaps under the window through which moisture can enter. If the joint of the frame and wall is leaking, this space is filled with heat insulation or mounting foam. Only then does the internal window sill set.


The new window sill should fit in after the old one. If this is not the case, then the hole must be widened on both sides. The window sill’s stability is ensured by placing it on the inside of the wall and sliding it under the window frame or a step profiled in it. The ends of the window sill, especially the heavy, stone one, can be additionally wedged in holes made on both sides with a depth of 1-2 inches. This is not necessary when the window sill rests on a sufficiently wide fragment of the wall (it will protrude beyond the wall support less than half the width). Wooden window sills can also be supported with brackets screwed to the wall.

We put the new window sill into the recess and wedge it so that it is in a horizontal position pressed exactly under the window. You should buy wooden wedges here, which you drive under the windowsill. It is enough to secure the wedged window sill against dirt with painting tape and protective foil.


What to attach the window sill primarily depends on the material from which it is made. Stone, conglomerate and wood window sills can be attached with polyurethane foam. This is the best way, because if the window sill is damaged, it can be removed by simply cutting off the foam. If you do not use low-pressure foam, with such installation, a stone sill is enough to wedge well into the wall, while long and slender wooden or conglomerate sill should be pressed from above. The foam, expanding in the space under the windowsill, lifts it. As a result, the window sill may bulge (wooden) or crack (conglomerate) in the middle. Therefore, a board is laid on it and spreads out with a lintel stamps.

To give the window sill a slope towards the interior, wedges are placed under the punches. After the foam has solidified, preferably on the next day, cut off the excess with a knife, remove the wedges and fill the plaster defects with plaster mass. Finally, after painting the walls, seal the gap between the window and the window sill with the appropriate color silicone. Special adhesive mortars can be used to fix window sills made of natural stone. The condition is a dust-free recess with a formed slope. It should be remembered that special mortars with white cement are used for marbles. Otherwise, the stone may become discolored.

For embedding the window sill, when it is recessed into the walls and pushed under the frame, you can also use mounting glue. It is suitable for all materials, except for marble (unless we use colorless glue). When the window sill is attached with assembly adhesive, there is no need to expand.

Tags : replacement sash windowsill