Best silicone for sealing masonry?

[Another John]

Hi all

Is there such a thing as "the best" silicone for sealing a gap in masonry?

The specific application is: we have a step to the porch. The pointing at the point where the step meets the porch's brickwork has a thin crack all the way along it (movement of the step I presume). This permits water (when it's raining hard) to seep down behind the step, which then wets the brickwork (which is above the DPC), and consequently we have florescence(?) on those bricks when the sun gets out.

I figure on chipping out the pointing and replacing it with a silicone bead (possibly applying a thin layer of mortar on top of the bead for appearance's sake).

is there a reliable silicone for this job? It seems to me that when silicone first appeared in tubes, it was magnificent stuff. In recent years there seem to be dozens of different brands and types of "silicone", some of which to my certain knowledge dissolves in water.

Cheers John

[Steve Firth]

Another John wrote: [snip]

I suspect that you will find that the silicone that dissolves on water isn't silicone. It will be a sealant but is likely to be acrylic, not silicone.

For the use that you intend, I would use polysulphide sealant, not silicone. A good alternative is polyurethane sealant such as Sikaflex.

[Another John]

I asked about a silicone for sealing between a step and the brickwork to which it's faced.

Steve Firth replied thus

Thanks Steve (the only reply! I always feel embarrassed when there are very few replies: seems to imply I asked a dumb question!). I've now got some polysulphide sealant: Evostick: *bloody* expensive, but I'm sure this is what I need. The sealant shelves in the builders' merchants are pretty intimidating these days!

John