Question of the Week-starting 4/19/15

For repointing a house wall, typically, what is supposed to be stronger, the brick or the mortar?

and the Awards Committee


Mr Dave Fetty wins! Congratulations, Dave!

Your prize will be sent to the address that InterNACHI has on file for you.

Excellent question. Thanks!


We appreciate your support, Jeff. :slight_smile:

well done, sir.

Sweet! Thank you!

As I recall the prize is Now books? Would it be possible to get the Florida edition? I can’t wait to see it! :slight_smile:

It’s questions like this that will help insure this is successful. Hopefully these evolve into discussions as to ~WHY?~ so as to become more educational and not simply just another ‘contest’.


I asked… not sure, yet.

Repointing is the process of renewing the pointing (the external part of mortar joints) in masonry construction. Over time, weathering and decay cause voids in the joints between masonry units (usually bricks), allowing the undesirable entrance of water. Water entering through these voids can cause significant damage through frost weathering and from salt dissolution and deposition. Repointing is also called pointing,[1] or pointing up, although these terms more properly refer to the finishing step in new construction

A lot of folks call it tuck pointing.

Thanks Sam, but why is it important for the brick to be stronger than the mortar? Wasn’t lime added to the mortar mix in the past to make it stronger, but the practice has been discontinued since? Why? Does it have anything to do with the way bricks are manufactured nowadays?

Congratulations Sam.

Explanation as to why can be further learned over here for all.

We will continue to try and it is positive suggestions/comments, like yours here, that assist us in making the Awards Committee’s efforts helpful, fun and educational for us all. :slight_smile:

The bricks are stronger because if there is a failure in the wall, it is easier to repair mortar than to replace bricks. I think modern mortars use Portland cement. But sometimes masons may still use lime based mortars for repairs to try to match existing. I read lime based mortars are better suited for soft stone such as terracotta. I’m not sure about the newer bricks, anyone have any insight on that?
Oh, my friends call me Dave! :D;)

From above link:

There are three things that make mortar very different from concrete. Mortar has lower strengths, must have the ability to retain water and have a high air content. There are three widely produced types of mortar. Types M, S and N. Type M will achieve a compressive strength of 2500 psi at 28 days. Type S will yield 1800 while Type N yields 750. By way of reference most general concrete is in the 4000 psi range but can go as high as 8000 psi for special applications. The easy way to remember the strengths is by spelling out the word MASON WORKS.

M 2,500 A ----- S 1,800 ** O** ---- N 750

W ---- ** O** 350 ** R** ---- K 75 S ----

Types O and K are not made commercially and can only be used for non structural applications such as fixing old mortar that has fallen out.

Why not make mortar as strong as concrete? In America isn’t bigger better? Not with mortar. When you build a wall you want the block or brick to be the strongest part of the wall. When the wall shifts, and almost all do over time, the weakest part is going to break. If the brick or block were to break, then the fix would be building a new wall. If the mortar crumbles, provided you don’t let it go on for years, you simply need to repoint the wall (that means sticking mortar back in where the old mortar fell out). This is a simpler and more inexpensive fix. One important reason why masonry cement or a portland/lime blend works well in a mortar joint and straight portland does not is the high air content. Many walls are exposed to rain and water. In the winter many of these are in area where temperatures often dip below freezing. The mortar contains a certain amount of water. When water freezes it takes up more space than water. This means that it will expand and crack whatever is next to it. By intentionally putting lots of tiny air bubbles in the mortar, the expanded ice has somewhere to go without causing damage. Concrete generally has enough mass that this isn’t a problem.

A question that was asked long ago during my days of swinging a hammer…

Does the mortar hold the bricks together, or apart?