19th century brick joint thickness 3

[ajk1]

The brick masonry mortar joint thickness in buildings built in the 19th century is generally relatively relatively thin, compared to buildings built in most of the 20th century, at least in my area of practise in Ontario. I believe this is related to the lime mortar that was generally used at that time. They seem to have aged well, without masonry deterioration, as long as there are no unusual adverse conditions (such as broken downspout or flashing which concentrating water on the masonry). Does anyone know why this type of thin joint was abandoned and not used anymore, and how it is related to the line type mortar in use in those days? I am just curious.

 

[ajk1]

Thank you both. I did not mention that I am in Toronto, which is far from the ocean, so in my case I would not expect that oyster shells would be a part of mortar here in Toronto, though it is interesting info. Dik, the history that you have provided is fascinating and I will print it out and save it. Thank you.

 

[dik]

This is a copy of an eMail I received a couple of days ago from Peter Foley. With his permission, I'm posting it here; IMHO it contains a lot of very useful information:

I happen to be “lurking” on the Eng-Tips web site when I come across your posts regarding the whys and hows of use of thin joints in (mostly face brick). And why they are “out of style” and common use today.

To use thin jointed brick in a large building requires the production of tens or hundreds of thousands of face brick that are within, a 1/8” in thickness and length AFTER firing. Which as you probably know is respectively 2X (the tolerance allowed) for height , and 4x the variation allowed for length in a 8” x 4” x 2 2/3” Nominal modular brick prism, that lays 12 whole units to fill a 16” x 16” module,

See hydraulic repressed brick machines that repressed the stiff but still pliable brick to an exact prefired dimension, and development of techniques that produce mostly useable consistent color and texture for the face bricks.

And the ability to produce hundreds of Tons of clean and GRADED sand that didn’t have ANY particles larger then 1/3 -1/2 the joint’s width 99%+ of the time at the wall being built.

All other things being equal, a thin joint has less exposure to the weather, = more years between tuck pointing in the modern sense( replacing the damaged mortar with new mortar that matches the remaining sound mortar.)

But perversely, tight joints cost much more to repoint without molesting the glaze on the old brick….

For almost two hundred years though tuck-pointing was faking “thin” joints in brick colored mortar pointing, a ~1/8 wide and deep void was left/created in the repaired brick tinted mortar and filled with lime putty and fine sand(mostly white) to create an appearance of “tight” jointed face brick…

Naturally, tight jointed wythes have a fraction of the plasticity of the 2 and 3 x thicker joints.

The intent often was the illusion of dressed ashlar stone work instead the far cheaper face brick.

And rarely did the story poles of the face brick and back up wythes have the same # of courses causing issues with header course wall ties etc.. returns to Party walls and alley ways laid out of common brick.

As the thin joints have ~33% if the space of regular joint sizing, the pre diamond saw mason would require near prefect planning for window bucks and all other Architectural openings to work with having to “cut” a brick to fit and leave an usable 1/8” head joint.

As to “ no standard brick size till 1700s” I have to call BS, the need for the 6:3:2(or 8:3:2) or (10:5:4) ratios(plus mortar joints ) of the a “common brick are SO obvious to almost all who use them, odd proportioned brick would require MUCH MORE expensive mortar (lime) and have over sized joints that Wouldn’t weather well. Most likely Bricks or Basketweaving,(arrows?) were the first “mass” produced items were ‘standardizing” has such an immediate and lasting increase in value, apparent to the meanest intellect.

And I find it very hard to believe the Sovereign powers did not create “standard bricks for large projects”, Anyone who ever tried to use varying sized junk material to build a level plumb and FLAT wall would know so, Imagine some retarded kid mixing three different brands of “Lego” toy blocks….

See “Rusticated stone joints” for the opposite trend/fad?

As an aside, to the relative depth of brick manufacturing tech that is fast being erased from our cultural memory is the wire brick cutter that was patented ~ about 80+ years prior to the nearly identical bread slicing machine…. Evidently, not many brick makers ever ran a bakery 1860-1930s.

The current Nominal 3/8th, 10mm joints allow the use of FAR cheaper extruded bricks that ARE not repressed….. and allow the current ¼” height, 3/8” depth by ½” variation in modular bricks, and the use of graded sand with particles including <1/8” making the cement paste demand far less( thus cheaper) then sand screened to “plaster” grade.

As to thin brick, the absorption rate of the units would matter more if they sucked up all the bleed water and then some of the water needed to cure the mortar/cements, it would make a weaker wall in tension/flexure… the “big joints “ are going to perform better in high moisture demand times. Porous brick would need adequate “prewetting” for proper bonding .

We can’t make good decisions on where to go, if we forget where we have been only few short generations ago.

Peter F Foley

His last eMail had a comment that if engineers understand the products they are speccing, they will more likely use it. It's all part of understanding the materials.

Dik

 

[dik]

ajk:
I worked in Toronto for about 30 years. They have some lovely 'old' stone structures; not old by European standards but older than me... That's where I first got interested in masonry restoration. There was an old brick building at John and King. It had been cleaned using sandblasting and the fireskin was seriously damaged... common to a lot of buildings back then.

Dik

 

[masonrygeek]

Good information from all! A couple of other things to mention.

Old walls with thin joints didn't have wall ties connecting the wythes together as they do now. Older walls used headers (stretchers turned at 90 degrees) so there was nothing in the joints (other than mortar). Most masonry wall ties are at least 3/16" in diameter and wouldn't fit in a thin joint. This disturbs a lot of architects who want to achieve a thin joint, but can't tie the wall back easily.

As horizontal bed joints get thicker (over 3/4") they have lower compressive strength values... and thinner joints have a higher strength. That doesn't matter that much any more since most of our brick walls are veneer and not loadbearing (sigh - too bad).

 

[ajk1]

Older walls used headers (stretchers turned at 90 degrees) so there was nothing in the joints (other than mortar).

My experience with masonry restoration many years ago here in Toronto with late 19th century exterior brick masonry with thin joints is that they did NOT have stretchers turned at 90 degrees for the ties, but rather had stretchers turned at an angle other than 90 degrees, so that if you look at the exterior face of the brick the stretcher ties are not visible. I don't know how they did this, maybe by cutting the exterior brick so the the angled stretcher fitted into it. Perhaps dik has seen this too and could comment on how it was done. An example of this is Wycliffe College building at Hoskin and Queens Park; I think I saw this also on at least one or or two other buildings, but I am getting quite old and cannot remember which buildings they were. I think if you look at any 19th century brick in Toronto, you will not see the stretcher tie courses from the exterior. I will look next time I am downtown.

 

[dik]

Sorry... I've never encountered that type of stretcher coursing.

Dik

 

[dik]

Information here will be included in my next update for historic brickwork.

Thanks

Dik

 

[masonrygeek]

ajk1 - You are referring to blind headers and they were used as well in multi-wythe brick construction. As you said, you can't tell from the outside that there are any headers. The mason would clip corners of the brick to lay them in the wall. Here is an old publication that shows the clipped or blind headers:

https://archive.org/details/in.ernet.dli.2015.462226/page/n213.

 

[ajk1]

ajk1 - You are referring to blind headers and they were used as well in multi-wythe brick construction. As you said, you can't tell from the outside that there are any headers. The mason would clip corners of the brick to lay them in the wall. Here is an old publication that shows the clipped or blind headers:

https://archive.org/details/in.ernet.dli.2015.4622....

Thanks. Diagram 4.116 comes closest to what I am describing.