Crumbling window sill

leakingpipe

Hi all,

We recently moved to a house needing renovation. The rear window sill was left partially panted and after the bad frost has now seemly become crumbled. What do you recommend doing, knocking it off and rebuilding or filling and repainting.

Thanks for any advice.

Ev84

Hi.

Yeah thats going to happen alright. Bare concrete being porous, water soaks in, on a frosty night then, the water freezes, expands and makes s**t of your sill. how badly is it crumbled? knocking off and re-building sounds the better option if it is thoroughly crumbled. Tap a metal hammer along the sill and if there are any weak sections or deep cracks you should hear a change in pitch/sound... like a dull hollow sound. Even if its not visible to the naked eye.

If it sounds and feels solid and it's just the surfaces that are messed up i would recommend a few skim coats/layers of cement or filler.

If you are going to build a new sill, be sure to use iron re-enforcing bars in your concrete cast as it may crack under certain stress, loads, tensions etc.. you must also leave a groove/channel along the underside of the sill to stop the rain-water running back onto the wall. Run your finger under any exterior window sill and you will feel it. This is where the rain drips off.

If you are just filling instead, don't fill that groove in or you could have dampness problems and mossy stains under the window.
if you are just buying a new sill then there's no problem. Be sure to paint it before a frosty night though...

Hope that helps

leakingpipe

Hi Ev84,
thanks for the advice. The cement is pretty crumbled, will have to get it replaced. Thanks again.