Drill pilot holes every 16 inches or so through the new sill s front and back edges.
Repair window sill concrete.
Fit the narrow tip of a bottle of silicone latex caulk into each crack and overfill it by about inch.
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.
A window sill is the bottom portion of the window and usually but not always has a lip that overhangs the trim molding and over time these can get damaged or even rot.
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.
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.
Fill the crack with multi purpose exterior filler.
Resist the urge to keep touching and fiddling with the look of the smoothed caulking you will probably make it look worse.
If the sill is painted repaint the whole sill as this will give an overall better finish.
Gray would look modern.
Use the crow bar or chisel to slowly pry the windowsill off the window.
However you should be able to purchase grey exterior filler which will be a close match to the concrete.
Spread and flatten the caulk with a small putty knife.
Run a bead of waterproof marine grade adhesive along the old sill.
If the sill is plain concrete it will not need to be painted.
Repair any rotten spots on the old sill with epoxy.
Using a small putty knife starting at the window smooth the caulking flush to the sill.
Fix any small or medium cracks in your concrete window sill with caulk.
Repairing window sills isn t a hard diy and i try to share simple ways to make diy improvements to your home.
Remove the excess material build up on the putty knife.
You may also need to pry away trim material known as side casing.
Your sill probably isn t this fancy.
Scrape away any mess with the edge of the knife.