My house had several cable runs left from the previous owner that were cut and redone with every TV service they tried. A handful of the runs were brought in from the outside of the house through external walls. (My external walls are all brick.

The cables were all cut to about 6 inches in length and pointed down to prevent water from coming in when I bought the house.

I would like to remove these completely, but I have no idea what to fill in the hole with...

Can I just fill it with Silicone caulking? When I had Fios come out and rewire the box to use the clean cable runs and cat6 runs I installed in the attic, they used a translucent blue goo that hardened after about 10 minutes where they ran the cable into the house, can I fill it with that? If so, what is the goo and where can I buy it?


  • In my part of the world you can buy tubes of stuff called "builder's mastic" for sealing externally. I've used brown builder's mastic for weatherproof sealing around pipes through external brickwork. Oct 26, 2013 at 21:51

1 Answer 1


Hopefully those holes are actually sloped upward the entire way, but I would not count on it.

Silicon would be OK, especially deep in. But there's a product called Mor-Flexx which is specifically made to look and work like mortar. A tube of this would work better than any mastic, as you can really squirt it far in. Plus you can touch up any other cracked masonry you might have around the house.

I might also solve this exact problem using rapidset mortar in a pastry bag (to get the mortar deep into the brick). But this can crack brick over the decades if the mortar is harder than the brick and thus expands differently (a problem in historic renovation, as older bricks are often softer than modern mortar).

That said, the Mor-Flexx is easy and will solve the problem completely. You can then install a weatherproof cable entry point and all future installers will take the lazy way out and use it (who wants to drill brick if you don't have to?).

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