Repair Cracked Concrete Window Sill

Scrape away any mess with the edge of the knife.

Repair cracked concrete window sill.

Steel reinforcing bars are cast into the center of the sill to strengthen it. Here is the smoothed caulking. What would be an appropriate material to fill it with. Brush the sill with a soft brush to remove dust and dirt before applying the first coat of masonry paint after any of the following work has been done if required of course.

Allow to dry completely before applying a second and third coat. Sand down the filler when it is completely dry. Fit the narrow tip of a bottle of silicone latex caulk into each crack and overfill it by about inch. Other option measure it all up make up a timber mould and cast a new one fix either a piece of half round dowel or sash cord to create the drip cast the cill upside down this method will be better than trying to cast in situ plus no weak joints.

Using a small putty knife starting at the window smooth the caulking flush to the sill. If you have the pieces just clean off any loose mortar from the block. Remove the excess material build up on the putty knife. Use mortar mix on the block and replace the pieces.

Water is sometimes able to penetrate the concrete because of damage to the surface or just deterioration over time. Finishing the mortar joint. Concrete has high compression strength but low resistance to bending tensile strength so the steel reinforcement is necessary. Resist the urge to keep touching and fiddling with the look of the smoothed caulking you will probably make it look worse.

I have on hand a tube of big stretch caulk and a tub of dap bondex ready mixed concrete patch. Fix any small or medium cracks in your concrete window sill with caulk. If the sill is painted repaint the whole sill as this will give an overall better finish. Any cracks can be sealed with the mortar mix or cement based caulk.

I have an exterior concrete window sill that has a crack in it that i want to patch pic attached. However you should be able to purchase grey exterior filler which will be a close match to the concrete.