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Old 12-08-2019, 08:04 AM   #1
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Will fresh mortar bond to week old mortar


I'm in the process of repointing an 1930s era stone basement wall, and I'm wondering if I should repoint all at once, or if I can work section by section.

I didn't really see a problem working section by section but I'm no expert.
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Old 12-08-2019, 08:49 AM   #2
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Re: Will fresh mortar bond to week old mortar


after 10sf, you too will be an expert actually ALL the work should be done at the same time but that's impossible,,, otherwise you'd be on your feet for 24-36hrs or more we all work in sections - grind / plug chisel / however you prep, vac out dust, mist w/wtr, & point away
we can do about 200sf per man day on brick jnts but that's if the jnts are uniform & we can get tooling as needed,,, stone's typically much slower due to varying jnt sizes,,, raised grapevine's the slowest,,, obviously some guys are faster than others
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Old 12-08-2019, 09:42 AM   #3
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Re: Will fresh mortar bond to week old mortar


The only thing I would add to STADRY advice is to use a matching mortar for mix design & PSI to match the original.
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Old 12-08-2019, 01:22 PM   #4
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Re: Will fresh mortar bond to week old mortar


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Originally Posted by ClarenceBauer View Post
The only thing I would add to STADRY advice is to use a matching mortar for mix design & PSI to match the original.
What do you mean? what I do know is that old mortar has a psi of about 30... No joke, the stones are in great shape by that mortar is trash. I wonder if it was just a lime and sand mix, from what I read that's all that they used before Portland cement.
BTW I used to mix batches for Quikrete..
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Old 12-08-2019, 02:32 PM   #5
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Re: Will fresh mortar bond to week old mortar


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Originally Posted by BagguetteMan View Post
What do you mean? what I do know is that old mortar has a psi of about 30... No joke, the stones are in great shape by that mortar is trash. I wonder if it was just a lime and sand mix, from what I read that's all that they used before Portland cement.
BTW I used to mix batches for Quikrete..
Portland Cement was available in the1930's.
If your existing mortar has a beige color it is most likely a lime based mortar.
Also look for very small pieces if white particles in the existing mortar they will be about the size of pencil lead in Dia. if you find this and the white particles are Lime & will be soft. If you find this type mortar than look into using a Lime Mortar replacement like Natural Hydraulic Lime (NHL).
You will find NHL 2 which has a very low PSI maybe around 70 PSI.
NHL 3.5 will have a PSI of 750. this one will most likely fit your needs.
NHL 5 would be used below grade.
DO NOT USE A PORTLAND CEMENT TYPE if your existing is that soft.
Check to see if you have a Lime Works dealer in your area.
Also look for US Heritage Group. , Edison Coatings or Cathedral Stone for a Lime Mortar.
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Old 12-08-2019, 03:14 PM   #6
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Re: Will fresh mortar bond to week old mortar


The 30's was a time when a lot of builders were starting to gauge OPC into the lime mortar. If using an NHL lime allow extra time for mixing up, and keep the pointing damped down for at least a week.
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Old 12-08-2019, 03:52 PM   #7
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Re: Will fresh mortar bond to week old mortar


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Originally Posted by ClarenceBauer View Post
Portland Cement was available in the1930's.
If your existing mortar has a beige color it is most likely a lime based mortar.
Also look for very small pieces if white particles in the existing mortar they will be about the size of pencil lead in Dia. if you find this and the white particles are Lime & will be soft. If you find this type mortar than look into using a Lime Mortar replacement like Natural Hydraulic Lime (NHL).
You will find NHL 2 which has a very low PSI maybe around 70 PSI.
NHL 3.5 will have a PSI of 750. this one will most likely fit your needs.
NHL 5 would be used below grade.
DO NOT USE A PORTLAND CEMENT TYPE if your existing is that soft.
Check to see if you have a Lime Works dealer in your area.
Also look for US Heritage Group. , Edison Coatings or Cathedral Stone for a Lime Mortar.
Why can't I use a Portland Masonry blend?
The old mortar is beige with white specks. Mostly sand in my opinion.

I don't see any reason not to use a Cement blend of mortar, it would be stronger.

The other problem I'm finding is there is a lack of any mortar once I've dug into it some. There are some voids within the wall that are just that, voided.
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Old 12-08-2019, 04:25 PM   #8
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Re: Will fresh mortar bond to week old mortar


The use of Portland Cement mortar in repointing the existing Lime Sand mixture will cause failure of the remaining original mortar it is to hard & dense causing the failure.
Call one of the company's above & talk to one of their Reps. that has knowledge of repointing older mortars it will be worth the few dollars for the call.
Also look up Preservation Briefs # 22 look @ page # 15 " Materials for Brick & Soft Stucco."
This one will have more info than you want, " Historic Scotland's Conservation Center. " U. S. Heritage Group is the U.S.A. partner.
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Old 12-08-2019, 05:44 PM   #9
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Re: Will fresh mortar bond to week old mortar


Wait, call who? Is there a specific inspector I could call to have advise me, that way they get to have a first hand look at the foundation? Being that I'm in a flood zone, would that change the mortar type I should use?
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Old 12-08-2019, 06:06 PM   #10
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Re: Will fresh mortar bond to week old mortar


The person to call would be a Manufacture Rep. for the type of mortar to use.
They can answer your question better than someone on the internet.
Below grade & in a flood zone if salt water is involved yes you should consult the manufacture or an engineer that deals with your situation.
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Old 12-08-2019, 09:01 PM   #11
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Re: Will fresh mortar bond to week old mortar



Just an FYI,
I still say Type S masonry mortar will do fine

Last edited by BagguetteMan; 12-08-2019 at 09:04 PM.
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Old 12-08-2019, 09:38 PM   #12
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Re: Will fresh mortar bond to week old mortar


In the last photo is the mortar to the right side of the voided area a hard mortar?
You can use any mortar of your choice you own the home.
If you were to have an Architect / Engineer spec. a repair type mortar & he / She was required to sign off on the type mortar recommended it would not be type S Portland Cement.
I worked in the Historical restoration Plaster & masonry trade for 41 years & the wrong type of mortar to repoint old soft mortar was a BIG money maker.
It would cause problems beyond mortar replacement. It may take 5 / 20 years but the longer it existed the higher the repair cost.
Keep in mind the higher the moisture migration the worst the problem will be.
Again save your self from a big mistake Call U S Heritage Group.
Than post what they tell you a the material they say to use.
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