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!
Assessing the damage
Before you begin, you need to assess the damage to determine the extent of the required repair.
- Is it simply a case of chipped and flaky paintwork that needs tidying up?
- Do you have deeper cracks that need filling?
- Is a more extensive rebuild required?
Once you’ve diagnosed the problem you can get cracking, filling in those cracks!
Freshening up the paintwork
You’ll be pleased to hear that this is a relatively easy job. Use a stiff wire brush to remove all the loose paint and dirt, before rubbing down the existing paint with medium grade sandpaper. Be careful to rub down the edges where any larger flakes of paint came away, so that you have a nice smooth gradient for the new paint.
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.
Repairing small cracks
Follow the same initial process as with the above method, but pay extra attention to making sure that any cracks are free from dirt and moss — a clean surface is essential for the filler to adhere correctly.
Using a spatula, apply a ready mixed masonry filler like Sandtex to the cracks, taking care to fill them fully and correctly. Allow to dry before sanding flat with medium sandpaper and painting as above.
Rebuilding the sill
Determining when a sill repair requires professional assistance can be tricky, but if there are large chunks missing or the sill appears to be cracked all the way through, it’s probably time to call the pros.
It is possible to fill in quite sizeable holes with the masonry filler method, but if the edges are crumbling away you’ll need to build moulds to shape the sill correctly – a job that’s probably beyond most DIYers skill level.
As you can see, with anything but the most severely damaged example, repairing a concrete window sill yourself is entirely possible. However, if you still think it’s a job too far for you and you’re in the Leeds or Harrogate area, feel free to give us a call or drop us an email and we’ll happily pop around to give you a quote.