Sika Mortarfix for repointing -- any experiences?

mahatmacat1October 21, 2008

I found this at Home Depot, and if it can save me trouble and make repointing our chimney easier and not compromise final quality, I'd like to use it. It's in a caulk tube, which is much easier to apply, rather than a bucket or bag (like grout) that I'd have to apply with a hawk and trowel, etc. -- it evidently has some latex in it -- is it something like caulk or does it look like mortar? Can I use it for complete repointing or is it only for spot fixing?

And a further question about repointing tools: I see the mortar tools, with curves in anywhere from 3/8 to 5/8 width, but then I see a specific "repointing tool" that's *flat*, at 3/8". Should I aim for a flat fill for the grout, which would suggest a flat smoothing tool, or should it be slightly indented, which would suggest the curve?

Thanks in advance for any help on these questions.

Here is a link that might be useful: sika elastomeric mortar fix

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mongoct

That tube could be used for spot repairs, but if you have a large portion that needs to be redone, well...then it's sometimes best to bite the bullet and have it redone.

Historically, pointing is normally done with a softer lime mix than today's straight portland-cement mix. "Softer" meaning that it has lime added to it.

Straight portland-sand it very hard, and if it's an old "soft" brick chimney, the mix can be harder than the brick resulting the brick failing over the years.

By adding lime, the point work is softer than the brick, and in some ways, self-healing, as it receives and gives off moisture. It results in a joint that is less likely to crack, and as a result, will stay water-tight.

That's for old soft brick and old soft lime mortar.

Modern chomneys, built with harder brick, are usually built with a harder portland mortar. It doesn't flex as the softer mortar and brick used to do, because today's brick is not as soft as the old formed brick of yesteryear.

You can take some "old" mortar and try to dissolve it in water (or it might need acid to dissolve), the more modern portland mortar will definitely need a dilute muriatic acid solution to dissolve. After it has dissolved, you can decant the liquid, the solid that remains is the sand that was used in your original mix. You can try to color match that locally to get repairs that better blend with your existing chimney's jointing.

All the above depends on how historically accurate you want to be, and the age of your chimney.

As to the tooling, use whatever tool will best match your existing joint. Concave, convex, "V", a straight raked joint...whatever one you wish.

If you do a total repointing job, meaning you've cleaned out the joints about 3/4" to 1" deep, it's sometimes easiest and faster to use a mortar or grout bag (like a cake/pastry icing bag) to get the mortar into the cleaned out joints.

Wet/mist the joint first, then bag the joint, when it firms up you can rake/form the joint and then sweep the face of the chimney to clean.

Flyleft, you are one busy girl!

Mongo

    Bookmark   October 25, 2008 at 12:22PM
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mahatmacat1

Ah! I couldn't figure out how you knew I was planning this! Should have checked over here...no one answered for so long that I gave up. But then of course you came through :)

So we had chimney people over yesterday, and they told us we didn't need the whole thing redone, just the west side above the roof. We do have to do the 3/4" in on the areas we have to do, though. But not having to do the whole thing: that's good news. It's also not all that visible, so that's even better news :)

Our house is a fine 1978 vintage, and I've been able to get enough out to take it to match. And o.k., I'll return the nice caulk stuff and get the real mortar and do the grout bag approach. *heavy self-pitying sigh*

Thanks so much for taking the trouble to answer in your usual excellent detail. You're helping even if you can't come out here and supervise in person :)

    Bookmark   October 28, 2008 at 4:33PM
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