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longrifle100
Parge over lime mortar?

I've got an old 1890's house in the midwest with lime mortar and soft bricks. The front (street) side of the house was done with a better quality brick and has held up with minimal repairs.

However, the other 3 sides, and especially the ones that face south and west, have a lot of mortar deterioration. You can see where there have been many attempts at re-pointing and repairs over the years, where it now looks like a patchwork. There are still holes in the lime mortar popping up. There are several houses built this same way on the block, and other neighbors have had problems with bugs/bats crawling in.

I'd really like to just parge over the bricks and mortar and previous repairs. But I've found conflicting info about mortar or parging with soft bricks and lime mortar.

Is there a lime/sand/portland mix ratio? Or lime/sand only? I've read that anything with portland cement will be too hard and too water resistant causes the bricks and remaining lime mortar to fail.

Do I need to use a bonding agent or just water? I really don't want to dig out all the existing mortar and re-point, so that's why I'm looking at parge options.

Thanks

Sombreuil_mongrel
Re: Parge over lime mortar?

To get the parging to key into the bricks, you'll need to remove the old mortar joints anyway, and that's more than half the job of re-pointing. Unless you want to put up wire lath and stucco it, that's the only way to get parge to adhere to brick.
Make sure there's plenty of lime and only a little portland in your parge mix or it will fall off and/or cause moisture problems.
Casey

Clarence
Re: Parge over lime mortar?

I agree with Casey on the use of Lime mortar. Also on removing all the old mortar in the joints to a depth of abouth 1 1/2 "
If any portland cement was used in the previous repairs it all must be removed due to the fact that it will cause failure of the lime mortar around it.
For a replacement mortar see if you can find NHL ( Natural Hydrilic Lime ) mortar this would be the best to use with the soft brick.
If you want to use a Lime - Sand - White Cement mixture try this one

2 Parts dry lime
1/3 Parts White Cement
7 / 9 Parts Sand

If you parge it is My opinion to not use lath over bricks.

Re: Parge over lime mortar?

Hello longrifle,

I'm the national sales manager for a historic masonry materials manufacturer based in Chicago (US Heritage Group). Previous posts do have some good advice but I thought I'd chime in...

Do not use portland cement as it permanently sticks to old masonry, traps moisture and releases sulfates that react with soluble salts in the wall to cause permanent masonry damage.

Do not use a bonding agent as it is unnecessary and it will trap moisture in wall causing mortar and brick damage.

Do not use type s dry hydrated lime as this is a plasticizer for portland cement not a proper binder for mortar.

Do not use lath as it will rust which causes swelling that cracks the soft lime parging.

Here's what you need to do:

-remove all paint, waterproofing coatings, biological growth
-remove all loose/deteriorated parging
-remove all portland cement based repairs
-remove loose pointing mortar
-cut edges of damaged parging areas perpendicular to direction of wall(do not feather edge patch)
-remove dust & debris (wash with low pressure water only & brush if necessary)
-allow areas that need repair to dry to 15%WME (wood moisture equivalent, can buy these meters cheap at big-box store of your choice)
-repoint as necessary using lime putty mortar, for finish rake back new pointing mortar to leave enough of the brick edges exposed for a parging key (1/4"). Be sure to follow lime mortar pointing and curing procedures, let me know if you need more info.
-repair parging using lime putty stucco (slightly more permeable but less durable) or natural hydraulic lime stucco (more durable but slightly less permeable). Be sure to follow proper preparation, installation and curing procedures.

We manufacture and train contractors how to use the materials that you need in the Midwest (Chicago). Let me know if you need any additional information.

Clarence
Re: Parge over lime mortar?

I did attend your workshop in 1999.
Instructors were Mario & John Machnicki,John Speweik and Bob Bennett.
It was a very well run workshop.
I also agree that your products are the best how do you convince the home owners as to the correct products to use?
To get your products it is almost impossible for the DIY type project.
So as to try to protect the Historic product what advice do you give the DIY homeowner?
On your order form page # 2 Lime Puddy Stucco ( Add Portland Cement Pouch )? Year 1872 - 1931 ?
Question is your Lime Puddy Stucco a hydrolic lime?
My advice to use the Lime Cement Sand is better than the premix as sold on the market for this type repair would you agree to this statement?
To be frank I can't convince the owner that the cost of the material over rides the use of the wrong product.
But than most of My work comes from the wrong product being used in the first place.
It kind of goes back to the 1950's You can pay Me now or you can pay Me later. Later is GOOD FOR ME.

Re: Parge over lime mortar?

Hi Clarence,

Thanks for the feedback and kind words. I responded to your individual questions below...

Clarence wrote:

I did attend your workshop in 1999.
Instructors were Mario & John Machnicki,John Speweik and Bob Bennett.
It was a very well run workshop.
Q) I also agree that your products are the best how do you convince the home owners as to the correct products to use?

A) Education is critical. Unfortunately the results of using the wrong materials are more and more pervasive in areas with historic masonry. We are taking action to get more information out to more that people need it. Stay tuned for details

Q) To get your products it is almost impossible for the DIY type project.

A) We answer questions for and ship material to DIY projects every day. I will say that we need to reach a lot more people and it's impossible to get our products if you don't know why you need them and that we exist.

Q) So as to try to protect the Historic product what advice do you give the DIY homeowner?

A) Read National Parks Service Preservation Brief Number 2 (and the others, they provide a wealth of unbiased high quality information for free). Replace like with like for like performance, there is no other safe approach.

Q) On your order form page # 2 Lime Puddy Stucco ( Add Portland Cement Pouch )? Year 1872 - 1931 ?

A) Branding for these products will change very soon. The message about the introduction of portland cement during that time is important but the branding can cause confusion as many buildings were built during that time without portland cement. The only reliable way to know is a mortar analysis.

Q) Question is your Lime Puddy Stucco a hydrolic lime?

A) We manufacture both. Heritage Pure Lime Putty Stucco Type L has no hydraulic binder components, only aged high calcium lime putty. Heritage Hydraulic lime mortar is made with time-tested natural hydraulic lime from Europe for predictable performance

Q) My advice to use the Lime Cement Sand is better than the premix as sold on the market for this type repair would you agree to this statement?

A) Hydrated lime based Type-O will be more permeable and will have less compressive strength than Type-N mixes typically sold and used for new construction and restoration. Hydrated lime does not perform as well as lime putty. Historic buildings that used early portland mixes (1872-1931) would typically be mixed with lime putty. Unless early Type N or Type O formulation is confirmed by mortar analysis Type O is still is likely not be good enough to reliably prevent long term damage depending on the original mortar, masonry unit material and masonry unit condition.

Q) To be frank I can't convince the owner that the cost of the material over rides the use of the wrong product.

A) We have tons of pictures that show what happens when the wrong materials and techniques are used. There are a few on our website. It is easy to see the damage (spalling, efflorescence, biological growth) that occurs by wandering around and area where historic masonry buildings are present. There are other problems but these are easy to see with the untrained, unaided eye.

Q) But than most of My work comes from the wrong product being used in the first place.

It kind of goes back to the 1950's You can pay Me now or you can pay Me later. Later is GOOD FOR ME.

A) Sad but true. One of three outcomes will DEFINITELY happen when incorrect materials and/or techniques are used on historic masonry:
-work redone with correct materials and techniques as well as additional work to repair damaged masonry
-facade/outer wythe torn off an replaced
-building torn down
None of these outcomes is good for the building owner or the building.

Clarence
Re: Parge over lime mortar?

Engelmann.
Thanks for your answering My questions.
I do agree with all of them.
I try to use like materials but run into the structural engeener specifing the incorrect mixture like the following.
Brick replacement
2 Parts White Portland Cement
1 Part Lime
7 to 9 Parts Sand
Mortar for joint reinforcing.
4 Parts White Portland Cement
1 Part Lime
12 - 15 Parts sanThe above mixtures are in Section 041000 Para. 2.2 Item A & B
Now I have to Bid based on these Spec. Now what's your opinion of these mixes?
My guess is about a min. of 2200 PSI in 28 days.
I won't get this job but maybe you want to check it out it's location is The Roberts House ( Historical Structure ) Gray Georiga.
Some body needs to talk to them.

Re: Parge over lime mortar?

Those are hard, dense, brittle mortars (type S and type M) which are never used in historic masonry. This is a common problem we see (structural engineers unfamiliar with historic masonry materials specifying based on concrete strength calculations). Google results say 165 years old? If it's original then there's no way that it was built with anything but lime putty mortar. The building will breathe and move to much for the mortar to tolerate. The bricks will be far too soft to tolerate Type S or Type M mortar and they'll be destroyed.

I don't want to hijack this thread so we can start another one and/or you can contact me any time at the office. My first name's Matt :)

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