Author Topic: Repointing old brick foundation  (Read 2516 times)

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Offline JHZR2

  • Posts: 28
Repointing old brick foundation
« on: April 10, 2018, 10:55 AM »
My 90-ish year old home needs a little bit of work when it comes to brick pointing. We had someone come do it maybe 9-10 years ago, and those spots are failing!

I think it will mainly be spot work, but I'd like to go all the way around the house and repair all the spots I see.

I am concerned about dust. Since I'm not particularly planning to do every last inch of every last joint, I'm kind of partial to hand tools.  But it's still a decently big job and time will be of the essence given family commitments. 

So I may get a grinder set up to help at least in some circumstances.

I have a decent metabo grinder, but no dust control setup. Could a Festool RAS 115 be adapted with a cutting wheel?  Can that tool be used as a grinder too?

I know bosch and others have dust collection attachments for their grinders.  So regardless of if RAS115 is in play or not, say I want to use my CT26 or CT mini. Anything I should know for mortar dust?

I had used my dewalt 20v hepa mini vac to clean out some holes I had drilled in concrete.  That thing clogged up horribly on the filter - had to replace it because the fines were so tenaciously clogged into the media.  I get it that it's a mini vac and not a high end extractor, and I know festool extractors are designed for plaster/Sheetrock work, which I'd guess may be finer than even mortar dust.  But should I be concerned using my festool extractor?


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Offline Bob D.

  • Posts: 931
Re: Repointing old brick foundation
« Reply #1 on: April 11, 2018, 09:50 AM »
I would get someone who has experience with restoration masonry work involved or at least research the composition of the mortar and be sure to use something compatible else it will fail and possibly destroy the whole wall.
It's a table saw, do you know where your fingers are?

Offline rst

  • Posts: 2153
Re: Repointing old brick foundation
« Reply #2 on: April 11, 2018, 12:23 PM »
You should be able to get a dust shroud for your Metabo, they make more grinders than anyone else.  I have two with the dust shrouds, a surface grinder and a slot cutter.

Offline TinyShop

  • Posts: 322
Re: Repointing old brick foundation
« Reply #3 on: April 11, 2018, 01:18 PM »
@JHZR2 - Your home is maybe old enough that lime mortar was used (likely weak lime since it already needs repointing - moderately hydraulic lime mortar would still be going strong). You mention that the recent work is already failing. This leads me to believe that the new work utilized cement-based mortar that was installed over lime-based mortar. This is a recipe for disaster, especially in the case of soft bricks or soft stone. The use of cement based mortars (which are much harder than historic bricks and lime mortar itself) in these instances (soft brick foundations and/or soft-brick exterior walls) results in the faces of the bricks literally blowing right off and premature failure of the cement-based mortar. I'm also guessing that you don't have gutters installed and that the regular damage caused by water collected by the roof falling down onto the drip line and splashing back onto the foundation contributed to the mortar failure. Moreover, you don't say where you are located but I'm also guessing that the temperature drops to below freezing in your area and that this, coupled with a lack of gutters, is another contributing factor.

You didn't provide any photos or a complete description of the problem so my comments are all supposition. However, I would encourage you to locate someone in your area (often times not an easy thing in North America) who is knowledgeable about historic masonry and who can verify the composition of the original mortar.

As an aside, if there are any streets in your area that are named "Lime Kiln Road" or the equivalent I can almost assure you that your mortar is lime-based.   
« Last Edit: April 11, 2018, 05:22 PM by TinyShop »
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Offline Rip Van Winkle

  • Posts: 301
Re: Repointing old brick foundation
« Reply #4 on: April 11, 2018, 05:11 PM »
90 years is considered old?

If you want to use a grinder on mortar joints or other masonry, you should use dust collection attached to the grinder. Just cutting a single brick with a grinder can leave you covered in dust, including your goggles, and trying to wipe away the dust tends to scratch up the goggles quickly. Cutting multiple masonry joints even on a mildly windy day can leave dust for a quarter mile around.

Metabo actually sold two or three dust attachments for their smaller angle grinders at one point, although I haven’t checked whether the attachments were still in production after the two sales of the brand recently.
One attachment was called the ‘Dust Director’. It was made by a US company that specializes in masonry cutting tools, and originally it was made only to fit Metabo grinders. Since then the company has added other grinder brand adapters. I presime if Metabo sold it it was decent, and the videos I’ve seen of them in use appear this way. A couple of the other attachments were made in Germany either by Metabo, or by another company that supplies different German manufacturers. None of the attachments was cheap, but they were still cheaper than buying a RAS115, and whould likely by better suited to the task.

Prices are somewhere on the website. Not all Metabo grinders will fit the same attachment so you might need to check with the manufacturer for your specific grinder.

Other manufacturers also make aftermarket dust attachments for grinders.
Dustless Technologies is one, their ‘CutBuddie’ can be adapted to different brands of grinders, and they’ve been in business for a while, or at least before US common power tools could be gotten with dust collection guards. Their guards are plastic though.

Some common US available power tool brands now offer dust guards either as standard with some of their tools, or as aftermarket accessories, which up until recently they didn’t in the USA. Bosch and Makita are two, the units are somewhat affordable compared to the aftermarket accessories. Flex is another brand that makes tools for masonry with dust collection, and well sealed bearings, but the tools are $$$$. Hilti offers dust collection guards for their grinders, but they’ve been changing their tool designs around, and you can never tell if the newer designs can use the older attachments or vice versa. Also, Hilti prices are $$$.

If you do use a grinder to remove a mortar joint, the safest way if you care about the bricks is to cut thru the center of the joint with the grinder, so the grinder cutter can’t touch the brick, and then go back thru with a chisel, cutting away from the brick at the top and bottom of the joint.

When applying new mortar, you have to hose down the brick before hand if it is any way porous, this soaks the brick, and prevents the porous brick from sucking watter out of the newly aplied mortar. If the mortar dries too quickly, the mortar will become chalky and deteriorate quickly.

Also, lime mortar has been used fir thousands of years, and is perfectly fine unless being directly rained on continuously. It’s actually more plastic than many modern cement mortars, and if a building in any way settles, the lime mortar isn’t going to crack like cement based mortars routinely do.

Offline DeformedTree

  • Posts: 445
Re: Repointing old brick foundation
« Reply #5 on: May 21, 2018, 08:10 PM »
Make sure you use a soft mortar (low strength) when tuck pointing back in, also the colorants they sell at stores are great, but take some trial and error.  You don't want to do all this work and have bright grey joints and everything else is aged brown joints, it will look awful.

Having done a lot of repairs, I used a circular saw with Diamond blade. A 10" circular saw like Milwaukee makes allows you to cut thru an entire brick, but this isn't needed or wanted if your are just tuck pointing. You could use a smaller saw with Diamond blade.  A benefit over an angle grinder is safety. It gives you a square base and holds a straight line.  It will be just like the grinder make a massive dust cloud.   Cut down the center of the joint, then use mason chisel to knock off each side of the cut.

I was by myself and have no vacuum attachment on said saw, so it was cloud of dust with me wearing safety gear.  You don't want an angle grinder to kick/bind.   In the end, buying the cheapest 5 or 6-ish inch circular saw the big box store sells, then taping your vacuum hose to it is probably a better bet.  If the tool dies, your out less than 100bucks.

Other important things,  vacuum the dust off the wall right away. Do not hit it with water or let it hang on there.  That dust plus water/moisture will ruin the brick.  I have lines from the foundation getting sawed that I simply can't remove from the brick, their wet saw make vertical splashes of dust+water mix that are permeant.  So make your cuts, and vacuum it all right away.   When it's all clean, then you can wet for adding the new mortar.

You can do it on a windy day, just make sure it blows towards the neighbor you don't like.  If you can have a helper run the vacuum behind you as you cut/grind that would be good, even consider making a funnel/scoop like attachment for the end of the hose, then you can control where the dust goes.