Install windowsill

The craftsmanship for installing a windowsill brings with it every skilled handyman. With the help of special mounting foam or glue can be dispensed with mortar work. When installing outdoors, special attention must be paid to tightness and insulation.

Install inside or outside

The basic principle of installation is the same inside and out. The precise cut is placed on the parapet and inserted flush with the window frame and the lateral wall edges. The edges of the joints must then be sealed with sealants such as silicone, which is not absolutely necessary on the inside. If you install a window sill outside, you have to ensure dense and durable joint edges.

Stone, aluminum or wood

Window sills are made of natural stone, aluminum or wood. While granite installation inside and outside is common and widespread, window sills made of aluminum or other sheet metal are almost exclusively installed outdoors. Conversely, for wooden sills, they are almost exclusively used indoors, because the sensitivity to weather and moisture is too great.

So a sill is installed

  • Assembly adhesive or
  • Ready-mixed mortar or
  • assembly foam
  • Joint sealant such as silicone
  • water
  • dish soap
  • spirit level
  • Folding rule or tape measure
  • protractor
  • Cutter or wallpaper knife
  • Wooden blocks and wedges
  • trowel
  • Possibly screw clamps
  • dishcloth

1. Prepare balustrade

If your parapet is made of bare bricks, you should roughly smooth coarse holes, heavy unevenness, and cracked corners with mortar. For hollow blocks, the retraction of a support plate can make sense.

2. Measuring and trimming

Measure the width and check that the side brickwork is perpendicular to the bottom window frame. If necessary, straighten the masonry sides with cement or mortar. Alternatively, you can cut the windowsill to the width of the narrowest point and fill the resulting cracks when grouting.

3. Mount the substructure

Place two to four wooden block towers or wooden wedges on the parapet surface and glue them after leveling with the spirit level.

4. Distribute mounting equipment

Fill the rest of the parapet surface with mounting foam or ready-mixed mortar. Alternatively, you can coat the underside and the edges that hit masonry and window frames with assembly adhesive.

5. Fit windowsill

Insert the sill at an angle from above into the window niche and lower the component slowly, applying slight pressure to the front. When the windowsill is seated, use the spirit level to measure the position and adjust the horizontal in both directions. If necessary, spray on mounting foam and wipe off any excess adhesive or mortar immediately.

6. Grouting

After the windowsill bed has dried (at least 24 hours), use a caulking gun to inject the sealant into the joints between the masonry and the window frame. Smooth the joints with a cloth rinsed in dishwater.

Tips & Tricks

Never work with too much pressure when fitting, because stones can break, splinter wood and bend metal. Adjust the width by cutting or grinding and grout accordingly more generously.

Video Board: How to Make Window Sills & Aprons