Replies

1. 
   inperfectionist | Nov 14, 2007 02:03am | #1

   Mac,

   I did an adobe job a couple years back. No portland in the mortar. Talk about soft mud. I'm looking at some of my notes here (don't know where I got this info) I'm seeing here 1:1:6 portland:lime:sand = 750PSI
   1:2:9 = 350 PSI 1:3:10 75 PSI. Theres folks in these parts know more than me,,,,, mabey they'll chime in.

   H

2. 
   ponytl | Nov 14, 2007 03:33am | #2

   you can buy lime at any farm supply store... i pay $8 for 50lb bags for the white fine hydrated lime...  you can make a lime puddy and then add sand...

   or... and this is what i do... not correct by any means... but at some point economics take over... and i'm not where we have a hard freeze... but i add some white portland... i use it pretty dry so as not to stain the bricks (we are talk'n tuck pointing here) i wet the wall to be pointed after i have cleaned out the mortar joints the best i can.....  i wet the wall alot... as you know the bricks suck in a ton of water... and you don't want them suck'n it out of your mix too fast...

   i mix 8-10 parts sand 2 parts lime and one part white type 1 portland... pretty sure this falls in the 500 psi range... but have no  proof...

   p

3. 
   WNYguy | Nov 15, 2007 12:06am | #3

   What "p" said.  In above-grade applications, I use lime-and-sand mortar with no portland.  Fifty-pound bags of hyrdated lime are about $8 from agricultural retailers.

   Most of my experience is with pre-Civil War buildings, before Portland cement was readily available.  With a "new" building like yours, it's possible the original mix may have had some Portland.  "P's" mix with the white Portland is about as "hard" as you'd want.

   We usually create a "lime putty" by adding water to the hydrated lime to create a peanut-butter consistency, and the mix the mortar 1 part putty to 3 parts sand. 

   If you want to match your repointing to the original mortar, you'll need to match the color and coarseness of the original sand.  Use muriatic acid to "dissolve" away the lime from a sample of the old mortar, then rinse and dry the sand completely.  That will give you a sand sample to match.

   For color-matching lime mortars, it's usually necessary, also, to tint the lime putty slightly.  We use powdered ochre pigment or sometimes commercial concrete colorant (a little goes a long way).

   Before repointing, be sure to wet the brick.

   After the repointed mortar has set up, we wire-brush it lightly to give it a weathered texture, then rinse with diluted muriatic acid, followed by water.  This cleans off the inevitable white film of lime from the brick and mortar.

   To avoid cracking, mist the new mortar with water, keeping it damp for several days.  Most of my experience is with stone masonry; perhaps this isn't as critical with the fine joints in brickwork.

   If you have deep areas to fill with mortar, you need to allow several weeks of above-freezing weather, or keep the work tented and heated.

   One of the great advantages of lime mortar is that it won't set up if it is kept moist and covered with plastic.  For larger jobs, it's possible to mix ALL the mortar at once, and use it at your leisure. 

   For example, for a barn foundation project I needed 72 cubic feet of mortar: 24 bags of lime, 3.6 tons of sand and eight cups of mortar pigment.  I rented a cement mixer for just one afternoon, and mixed all the mortar.  Then I did the masonry as time allowed over several months (even used some of the mortar the following year).

   Allen

    

4. 
   john_carroll | Nov 15, 2007 12:43am | #4

   There's a good chance that the mortar in your house is not a lime-only mortar. Portland Cement was invented in the 1820's and was first manufactured in the USA in the 1860s. If the joints are fairly wide (1/2-in., or so), I'd have to think that you have a portland cement/lime mortar.

   My brother has a 19th century rowhouse in Baltimore and did extensive repointing with Type N portland cement/lime mortar. This is different from Type N masonry cement. Masonry cement is portland cement based but uses admixtures other than lime.  

   To make Type N portland cement/lime mortar, get a coffee can or similar container. Fill it to the top 6 times with sand, once with portland cement and once with hydrated lime. Mix this with water to make Type N pc/lime mortar.

   To make Type O pc/lime mortar, use 1 pc, 2 lime, 9 sand.

   You should be able to get hydrated lime (mason's lime) by the bag at any masonry supply store. Ernest Meyer Building Supply in Bladensburg (if it still exists) might carry it.

   For more info on lime or for help in finding a supplier, check out the National Lime Association: http://www.lime.org/

    

1. 
   mackzully | Nov 15, 2007 01:00am | #5

   Thanks all for enlightening me about my mortar.Mudslinger, my joints, being that it was originally a lower class neighborhood when built, part of the "swampoodle", vary widely, but seem to be around 3/8". The existing mortar is extremely friable, but if I can get away with a type-N pc/lime mortar, then I'll give a bag or two a try.And I'll have to take a trip up to Ernest Meyer, a local neighbor recommended them as well!Thanks,
   Z

2. 
   WNYguy | Nov 15, 2007 05:24pm | #6

   "To make Type O pc/lime mortar, use 1 pc, 2 lime, 9 sand.  You should be able to get hydrated lime (mason's lime) by the bag at any masonry supply store."

   That sounds very reasonable, and what I'd probably use.  And by the 1890s, Portland cement was certainly in widespread use.   The homeowner's description of the mortar as "very soft" made me wonder if it might be lime only.  My experience is with early 19th-century masonry.

   And the the National Lime Association is indeed a great resource.

   Allen