external concrete window sill breaking up

Question

How should this be dealt with ? 
The concrete is breaking away from metal rod that passes through it. The break { hasseveral pieces ] is about 11 inch long & looks like its going to fall out.
It has been suggested that I repair it with Epoxy concrete & clamp it. ,also, that I should remove window ,& replace the sill . 
Best approach & idea of cost if possible please.

Billy · Accepted Answer

This is a very common issue with older concrete window sills and is usually caused by the steel reinforcement (metal rod) inside rusting. When it corrodes, it expands and forces the concrete to crack and break away.

An epoxy or patch repair will only be a temporary fix. If the steel has started rusting, it will continue to expand and the repair will fail again, especially with frost and water exposure.

Best long-term solution:
Remove and replace the sill rather than trying to clamp or glue it.

Typical process:
• Carefully cut out and remove the damaged concrete sill
• Clean up the opening
• Install a new pre-cast concrete or stone sill with proper fall/drip groove
• Seal and make good around the frame

You usually don’t need to remove the window, just the sill below it.

Charles · Answer

Best approach: remove loose concrete, clean the metal rod, and repair with epoxy or patching mortar, clamping until set. If the sill is damaged or unsafe, replace it. Costs vary: repair £100–£200, full sill replacement £250–£400 depending on size and materials.

Kind regards, CB Builders & Son

Jazz · Answer

This is a common problem on older concrete window sills and is usually caused by the metal reinforcement inside rusting and expanding, which then breaks the concrete apart.

A repair with epoxy or repair mortar can be done in some cases, but if the metal is exposed and the break is around 11 inches long, it’s unlikely to be a long term fix and the issue often comes back.

The best permanent solution is normally to remove and replace the sill. This is usually done by taking the window out, fitting a new sill and then refitting the window, which removes the rust issue completely.

Repair is cheaper short term, but replacement is the proper fix and better value long term. Costs depend on access, window size and sill type, so it’s best assessed in person.

Richard · Answer

Good afternoon, repairing the concrete would be absolutely fine, there's Mapei products that are suitable for the repair needed.
would recommend cleaning the reinforce bars with a wire brush then applying anti corrosion product suitable for concrete repairs.

James · Answer

Best to replace cill for proper job . but you can cut around it with disc cutter and clean it up with two pack filler it will last for a couple of years

Doug · Answer

Cost depends on size but yes get it replaced repairs don’t last and it’s money wasted as there is obviously an issue with the concrete and steel

Gary · Answer

Hi you can remove and replace without removing your window carefully it could be just a case of old out new in job dun no more issues

Ryan · Answer

Best way would be to replace the cill, but cost effective you can resin it and clamp or part filler

Dan · Answer

replace the cill, but for the most cost effective I'd resin it and clamp or part filler it also

Rob · Answer

I would recommend creating a former to match the other sales drill into broken cell and insert stainless bars fixed with resin clamp The former and fill with concrete

external concrete window sill breaking up

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