The most vulnerable part of the window is the outer window sill, which is exposed to various mechanical influences and gets wet in the rain. Rainwater falling on a painted or varnished window sill causes wood to rot. The decay process quickly spreads to other parts of the window block. Concrete windowsills can crack when exposed to moisture and frost. If the wooden sill is cracked or chipped, it can be easily repaired. Remove paint with solvent, remove wood chips and wood chips with a spatula and wire brush. Clean the gutter under the windowsill with an old screwdriver. Fill cracks and gouges with wood filler and let it dry. Then clean and paint the windowsill.
Rotting is already a serious problem. If the entire window sill has rotted, then perhaps the damage has spread to the entire window block and will have to be replaced. If a small area is damaged, it can be cut and replaced with a fresh timber section. Hardwoods are better at resisting decay, but softwoods can also be used as replacements if they match the material of the window sill. If only the front part of the window sill has rotted, then the replacement section is marked and cut out so that it is wider in the back than in the front. Then the replacement section is securely fitted to the healthy part of the window sill..
Surface potholes and small areas of damage on concrete windowsills can be cleaned out with a wag and a chisel, and then carefully repaired with mortar. A window sill with large damage, such as deep cracks, will require more renovation. To do this, you will have to remove the destroyed places, make the formwork in the shape of the window sill, press it tightly against the wall and the window sill and fill it with new concrete mortar.
Protruding wooden sill. The wooden section that hangs over the wall is attached to the sill of the window frame with a tenon connection. A U-shaped “drip” groove, hollowed out at the bottom edge of the window sill, prevents rainwater from accumulating at the rear of the window sill and entering the wall. Instead of the prefabricated sill shown here, the overhanging sill can be part of a single window frame structure.
Concrete sill. The lower transverse beam of the window frame of the swing casement is located on a concrete sill that hangs over the wall. The surface of the concrete window sill is sloped to allow rainwater to drain off. A stainless steel strip, which is embedded in concrete and located in a special gutter between the concrete and wooden structures of the window, prevents water from entering the room.
Replacing a damaged section in a wooden window sill
1. Marking the windowsill. Scrape off excess paint from the window sill, then use a screwdriver or other sharp tool to check the condition of the window sill and the size of the damaged area. Parts of the windowsill that are soft or spongy should be removed. At a distance of approximately 50 mm from the border of the damaged area, draw lines at an angle of 45 degrees towards the edge. Behind the damaged area, draw a pencil line connecting the two corner lines parallel to the edge of the window sill.
2. Sampling the decayed zone. On the protruding part of the windowsill, you can remove the rotten area with a hacksaw. In the part of the window sill that lies on the wall, the sampling along the lines is done carefully with a chisel and a mallet. Take care not to blunt the chisel against the stone wall.
3. How to cut the insert. Measure the height, width and length of the sill to be replaced and add 2mm to each measurement as a finishing tolerance. Using a tape measure and a thickness gauge, transfer the dimensions to a timber that is slightly thicker than the distant part of the window sill. Saw the workpiece along the marked lines, trim it to the desired thickness so that it tightly fills the selected part of the window sill.
4. Hollowing out the gutter. Draw two parallel lines on the bottom of the piece of wood so that they line up with the gutter on the remaining part of the window sill. Clamp the workpiece in a vise or clamp. Using a chisel and hammer (you can use a fluted chisel instead of a chisel) select the groove between the marked lines to the depth of the existing gutter.
5. Securing the insert. Drill fixing holes along the edge of the prepared section – approximately two holes for every 300 mm of the sill length – and countersink the holes. Lubricate the insert on the sides and back with waterproof glue and push it in place using a little mallet. If necessary, remove excess adhesive. Screw the insert to the window sill with copper chrome screws # 10. The screws must go into the window sill at least 25 mm deep. Fill the countersink holes and any cracks in the windowsill with putty. Use a regular plane to trim the inserted section flush with the windowsill. Then prime and paint the entire window sill..
Repair of a concrete window sill
1. Knocking out old concrete. Gouge out any chipped or damaged area with a chisel and hammer. Try to gouge the edge of intact concrete as evenly as possible, and the bottom, on the contrary, with potholes, so that the mortar will take better.
2. Application of a liquid cement mixture. Mix the cement with an adhesive, such as styrene butadiene rubber latex, as directed in the manufacturer’s instructions. Fill the selected cavity in the windowsill with the cement mixture. A solution of a cement mixture is prepared as follows: 1.5-2 parts of sand and 1 part of cement are mixed in an old bucket or other container, and water and an astringent are gradually added. Stir until a smooth paste is obtained..
3. Application of the solution. While the liquid cement mixture that you applied to the window sill is still sticky, attach a board to the edge of the window sill and use a trowel to fill the defect in the window sill with fresh mortar. Press the mortar firmly and, using a trowel, fill in any cracks in the potholes. Remove the board. Smooth the applied solution with a trowel or a shield, then cover the window sill with a piece of polyethylene and leave to dry for three days.