How to fill gap between paving and brick window sill?

Question

Hello, your advice on fixing the gap, see the photos is very much appreciated.

Emma

JacobZ · Answer

Hi @emmab1986,

Weep holes are always above ground level in brickwork. They do not work as intended if they sit below ground level, which is why I am being cautious about them in your situation. Typically, they will sit 1-3 courses above the concrete slab and sit directly above the line of your damp proof course.

Your damp proof course generally sits at the same height around the whole house, so if you can locate a weephole to the left or right of the window, then look at the mortar line beneath it, you should be able to find your DPC and then follow that mortar line around to compare its height to the window.

Let me know how you go. I will assist further if required.

Jacob

emmab1986 · Answer

Hi @Jacob ,

Thanks for the guidance.

Looking closely at this section:

* Weep Holes: I didn't spot any weep holes directly below the windowsill, though the sills sit virtually at ground level. Should weep holes typically be located above ground level in standard brickwork?
* Vertical Mortar Joints: I didn't see open perpends (gaps in the vertical mortar joints) right here, but I will double-check the adjacent brickwork further to the left and right.
* Damp-Proof Course (DPC): I couldn't see a visible membrane line (like black polyethylene or embossed aluminium) along the horizontal joints. Is it possible for the DPC to be concealed beneath the sill bricks or finished lower down?

Given the image attached, the gap appears to be settlement between the paved apron/concrete base and the underside of the brick sill. If we confirm that sealing this won't compromise drainage or bridge the damp course, filling it with a backing rod and a flexible polyurethane sealant like Sikaflex 11FC sounds like a solid plan.

Thanks!

Emma

JacobZ · Answer

Hi @emmab1986,

The first thing we should look at quickly before moving forward is where your weep holes and dampcourse are. I say this because if there are weepholes below that window, which is fairly common, then it wouldn't be wise to close up that gap as it is necessary for them to be able to drain and dry out. If your weepholes are covered, it can lead to issues with moisture which can deteriorate the brick and timber window frame.

If you look at the bricks to the left and right of the window, can you see gaps in the vertical mortar joins? If so, what height are they at relative to the window?

Can you see a solid line running along one of the horizontal mortar joins? It might look like black plastic or a silvery coloured line along the mortar.

If we can positively confirm that closing up the gap will not cause issues, then the solution is usually to use a foam backing rod to fill most of the depth first then seal over the top with a polyurethane filler such as Sikaflex 11FC Purform.

Let me know what you find.

Jacob