Repair Window Sill Concrete

Drill pilot holes every 16 inches or so through the new sill s front and back edges.

Repair window sill concrete. Fix any small or medium cracks in your concrete window sill with caulk. Repair any rotten spots on the old sill with epoxy. Trim the back edge of the new sill as needed so that its lower edge fits tightly against the siding and its back edge fits against the old wood. Resist the urge to keep touching and fiddling with the look of the smoothed caulking you will probably make it look worse.

Repairing a concrete window sill could appear to be a major job that s far beyond the skills of the average diyer but with the proper knowledge tools material and preparation you might find it s worth considering having a go yourself unless a complete rebuild is necessary. Your sill probably isn t this fancy. Spread and flatten the caulk with a small putty knife. Scrape away any mess with the edge of the knife.

Remove the excess material build up on the putty knife. Gray would look modern. If the sill is plain concrete it will not need to be painted. Using a small putty knife starting at the window smooth the caulking flush to the sill.

If the sill is painted repaint the whole sill as this will give an overall better finish. Use the crow bar or chisel to slowly pry the windowsill off the window. Use a utility knife and if necessary a hammer to carefully break and remove any caulking or sealant that s binding the old sill to the window frame. Fill the crack with multi purpose exterior filler.

You may also need to pry away trim material known as side casing. Fit the narrow tip of a bottle of silicone latex caulk into each crack and overfill it by about inch. Keep the sill in one piece so you can use it as a model when cutting the new sill. However you should be able to purchase grey exterior filler which will be a close match to the concrete.

Use cement or waterproof construction glue to attach the gutter to the window ledge then paint the gutter to match the other ledges or paint them all a different matching color to update the house. Run a bead of waterproof marine grade adhesive along the old sill.