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Windows 02-22-2010 11:59 AM

Repointing 90 year old chimney in western Wa
 
The chimney on the home we just bought, like the rest of the property, has not been maintained. The bricks appear to be in good shape, but the mortar between them has turned to sand. It can be removed with bare fingers without too much effort. I have been reading a little about repointing and it seems there is a lot to it both in terms of application technique and knowledge of materials. I have three questions. Is this kind of complete break down in the mortar typical for the age of the chimney and the the materials that were used at the time? Also, is this repointing project something I could reasonably tackle myself? (Given that I have no experience I am inclined call in the pros, but at the same time, I would love to learn how to do it.) Thirdly, can anyone recommend a book (technical but not too technical) to get me started? Thanks.

ccarlisle 02-22-2010 12:20 PM

The type of mortar is critical; it's not just regular mortar but mortar that doesn't expand when it gets cold. You'll have to find it at a dealer or somewhere but not at HD...

People use regular brick mortar and are surprised why their mortar and their bricks start disintegrating after a frost or two...they knew how to build 'back when' and mortar done properly can last for centuries as it already does...

Tscarborough 02-22-2010 01:26 PM

You can do it yourself, it is not hard, but it is dangerous since it is on the roof. Tuckpointing is relatively simple, you will be removing the old mortar to the required depth and then adding the new in increments.

3 things to note, though:
You will need to use a lime mortar from what it sounds like.
Do small areas so that you do not weaken the chimney structurally.
Save the final lift (increment) of mortar and do it all at once and from the same batch so the color will be uniform.

Just google "tuck pointing", there is plenty to read.

Gary in WA 02-22-2010 09:20 PM

http://books.google.com/books?as_brr...G=Search+Books

My son is at Eastern, I used to hunt at Curlew....

Be safe, Gary

Skuce 02-22-2010 11:38 PM

First off.

The proper way to tackle this would be to document the chimney completely and remove it. Measure the bricks (they won't be modern metrics) and measure the joint thickness. Then draw out a plan of the whole chimney. Lots of photographs and make a story pole

Then you are going to remove the chimney down to the roof line.

If you are in a Freeze/Thaw region. The bricks will be toast. They won't "look" bad. But they will be toast.

You will need to get a hold of a supply of reclaimed FACE brick. Face bricks are the best quality/hardness and fired properly. You can find LOTS of reclaimed brick places...but only talk to the ones that sort Face bricks from the salmons (underfired softies)and clinkers (over fired burned ones).

Then you are going to rebuild the chimney from the roof line up following all of your disassembly documentation.

You will be using a traditional pure lime mortar (Sand + Hydrated Lime "or" Slaked Lime Putty). If you use anything that has Portland cement in it....your chimney will take itself apart on you.


You maybe could repoint it in the mean time...only as a remedial action to buy you a bit of time until you can do the job properly. But you want this chimney to last another 100 year...not 5. So do it right the first time.

Also remember that the flashing and cricket on the chimney has to be done properly as well. No caulk-goopers allowed. Or you'll be in that "5 years and you'll have a problem" boat again.


As for a book to get you started:

Old House Handbook by Marianne Suhr


"Old House" specific Message Forums to get you started:

http://historichomeworks.com/forum/index.php

http://www.oldhouseweb.com/forums/

Windows 02-23-2010 12:54 AM

Thanks for the encouraging replies and the book suggestions. I hadn't heard of the Old House Handbook and will definitely check it out.

badbuz 02-23-2010 07:20 AM

Re-pointing the chimney is an easy job...ive been a bricklayer for 15 years and anybody can do it. First get a grinder and grind out at least a half inch of the mortar, after that take a hose to it and wash out all the loose mortar and dust (very important). Then any premix type "N" mortar at Lowes or Homedepot will do just fine. Get a trowel and a slicker and push the mortar back in, re-tool it with a jointer or re-rake it if the joints are raked.

Skuce 02-23-2010 09:36 AM

Never use a grinder unless you have 15 years experience.
And you can NEVER use a grinder to cut out the head joints. Maybe the bed joints if you know how to collapse the joint in on itself properly without touching the bricks.
I have seen Disaster grinder work where people skip out of the joint and all over the face of the masonry units (and those specific people called themselves professional bricklayers...no offence).

First timers should always use a small/narrow and long cold chisel and a baby sledge (>1.5lbs)
Safest way. The Mortar is expendable...the Masonry units are not

N types are still too far too high in compressive strength (750 psi) for historic clay fired brick (70-200 psi). Plus it doesn't breathe like a Lime mortar because of it's high Portland content. So the water will be forced through the bricks resulting in spalling.

Tscarborough 02-23-2010 12:15 PM

Getting paid for it does not make you a professional. As the man says, do not use a cementious mortar, and do not use a grinder. There are joint routers, but for lime mortar you don't need it, and probably don't need a chisel either.

stuart45 02-23-2010 02:12 PM

If it's soft enough to rake out with your finger then a mortar rake should do the job. If you need a chisel use a plugging chisel which is specially designed for mortar joints.
If mortar joints are so hard that they need to be ground out, it always makes me question whether the wall really needed re-pointing to start with.

Windows 02-23-2010 07:45 PM

Thanks for the replies. A picture of how to proceed is beginning to emerge. Just a few more questions. If a half an inch is the minimum mortar to remove, what is the maximum amount? Do I scrape mortar out until I get to something solid, or simply stop at certain point? Also I read elsewhere that a bonding agent is an important ingredient in mortar for repointing - should I be mindful of that using lime mortar, or is that strictly for cementious mortars. Also, if the repointing is done in sections and in coats, how thick can each application of mortar be? And finally, would I start at the bottom and work up, or start at the top and work down? Thanks again for the help. THis has been incredibly useful.

Tscarborough 02-23-2010 09:01 PM

Unless the joints are very deteriorated, you do not need to remove all the mortar. Soft mortar, in and of itself is not the issue. As a rule, it should be tucked in lifts of 1/4 to 3/8". With old brick and lime mortar, the tendency will be to suck the moisture out of the new mortar on contact. This is not a bad thing as it is what produces bond strength within limits, but to ensure compaction do it in lifts.

No bonding agent, as that will not breathe as the lime mortar needs to do.

It doesn't matter where you start, but if you can break bricks free by hand, then you should tear down the chimney and rebuild it from scratch.

You should also replace the crown and build it correctly as this is what causes most chimney stacks to fail.

stuart45 02-24-2010 07:50 AM

If you re-point with lime, make sure you protect the joints from the sun, or rain and frost for a while. Lime mortar hardens slowly by absorbing CO2 and can easily be damaged by drying out too quickly.
We usually use a moderately hydraulic lime for external works as recent analysis of the old mortars has shown that the mixes were often 1.5/1 or 2/1 sand / lime and a pozzolan such as brick dust was added to make the lime mix slightly hydraulic. Pure lime mixes of 3/1 sand/lime have often failed here in exposed positions.

Skuce 02-24-2010 09:41 AM

I'll second that. Protect the newly worked mortar (either freshly lain or repointed) Don't let the mix dry out (for about a week) or be exposed to freezing (for a least 2-3 weeks min)
So LIGHTLY mist it twice a day, not too much or the lime will run, and cover with damp burlap that has been covered in plastic.


That very good mix information to know. The mixes were that lime rich is slightly surprising at first...but makes sense now that I think about it.
The brick dust would also be great for toning the colour of the joints

The mixes that I've seen and heard about here are in the 2:1 to 2.5:1 range typically.

Allison1888 02-24-2010 12:00 PM

chimney
 
Great advice here and I'm facing the same type of project. I'm in the Chicago area and the estimates I've gotten for hiring a professional are astronomical-- in my opinion. The restoration company that will do it right with lime mortar, etc. wants $11,000 for two chimneys (one is not very high-- the furnace side). The other brick layers don't want to guarantee the color match or use the right materials. Does anyone know of a good, but not outrageously expensive source in Chicago? I think I could fly you guys in from Canada for less!

thanks!


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