Spalling brick

In Colorado. This appears to be the result of moisture absorbed by brick and then freezing. Some efflorescence is visible. Is this the result of poor firing practice?
I believe this home was built in the 1950s so this has taken something over 60 years to start happening. The brick face is obviously delaminating at a pretty uniform thickness.
Anyone want to shed some light on this condition?

B]ROOF / Chimney**

Lack of a proper chimney cap has caused excessive spalling caused by water freezing and popping off the brick facing and efflorescence observed on brick often caused by evaporation of water in saturated masonry material leaving salts behind.

Lack of proper chimney cap has contributed to this condition.

Recommend::: Mason tuckpoint and install proper chimney cap

I’m going to guess it’s a manufacturers defect.
We used to call them clinker bricks… Craftsman era utilized them as a decorative feature.
Likely moisture has frozen in the bricks and expanded as you say but it’s interesting that it’s only on the courses at the roofline and cap…?

"Brick spall when they are too soft and porous. This permits the brick to absorb and retain too much water which then can freeze and expand breaking away the brick surface.

While this is merely a general rule and not an absolute, there are two typical times when brick spalling occurs. The first is when brick have been reclaimed and re-layed as “used brick”. The second is a manufactured brick that was simply substandard.

The interesting thing about the first reason is that early American masons actually did understand brick density and vulnerability issues. They culled and set aside the soft brick for the interior withes of solid masonry construction. Unfortunately, masons in the 60’s and 70’s weren’t as thoughtful and installed them as exterior brick. It didn’t take long for them to fail.

Occasionally an inspector may notice spalled brick on the side of an old row house and assume this is an exception. But, typically, upon closer examination it will become obvious that even these exposed soft brick were not originally exterior brick. Another building which has been torn down once adjoined this building. The silhouette of the previous building will be apparent (outlined) through a change in brick appearance and quality of workmanship.

The second common circumstance under which an inspector will see spalled brick is in houses built in the 60’s and 70’s. Some brick manufacturers during that period of time were using inferior materials. When that fact became apparent, the ASTM devised absorption standards that some pits and manufacturers could not meet. They were forced to close down.

For these reasons, an inspector should not expect to see much brick spalling in homes built in the recent past or future.

As a side note, on occasion we may see brick that have come apart near the top of a chimney, but this is not typically spalling. When the crown of top joints fail on a chimney and permit water to enter and freeze in the cores bricks can literally spit apart. "

The chimney looks unlined. Was that the case?

Look at your photo again, the mortar is in good shape meaning the mortar is harder then the brick therefore the brick takes the brunt of the moisture and fails. Hence the reason for tuck pointing and parging in older buildings, the mortar has more lime in it and to gives the moisture a place to go and saves the brick. The reason for parging was to help give the moisture a place to go (wick) once it has delaminated you tuck point and parge again and the brick should be in good shape.

It does look unlined to me too. Also, what was vented into the chimney? Is the installed flue too big for whatever is venting into it and the exhaust is condensing inside of the chimney.

Liner or not look close at that cap guys. It has been sloped short and is cracked.

Looks like an antenna was previously strapped to the chimney also which is not advised.

The crown didn’t cause the spalling. That little crack didnt cause all of the spalling. It probably hasnt caused any problems at all yet. If I had to take a WAG, I would say a gas appliance in the chimney is causing too much condensation inside.

Hence my post.

You do not want the mortar to be stronger than the brick.

This photo is about 5 years old and I was there to inspect a valley only. I just took this photo in passing. Now I’m going through all my old photos for the Flash Card project and trying to give good explanations for the defects shown.

The damage location is kinda random, although it seems to be a little more concentrated at the corners. I’m thinking that the bricks delivered to the job included both high and low quality, similar in appearance and the mason used them randomly.

The damage appearance is similar, with the face delaminating in similar thickness. If the source of moisture was from above (leaking crown) or below (moisture laden exhaust gases meeting cold brick of unlined chimney), damage should be concentrated low or high, but there’s also damage in the middle.

I’ve added 3 more photos, including one of a different chimney on the same roof, with what looks like identical brick with no damage, indicating that the problem has to do with the construction of the damaged chimney.

But why is it just now failing after all this time and in such a random pattern)? The other chimney with brick that looked very similar had no damage.

My understanding of differences in hardness- well, actually tensile strength- had more to do with crack patterns than rates of deterioration of brick. This is the first I’ve heard of brick face delamination caused by… by what? Water running off the mortar?

(hadn’t yet posted the other photos when you made this post)

Spalling is caused when the masonry absorbs too much moisture from rain and is subjected to freeze/thaw cycles.
Damages can be exacerbated by condensation of flue gasses in improperly sized flue liners and gaps or cracks in mortar joints on the interior of the chimney, and by moisture entering the interior of the chimney chase from the top at the cement crown area where cracks or gaps allow water to enter.

If the cement crown is not built with a poured crown with 2” overhand and drip edge per code, damages to the top of the chimney structure will occur more quickly. However, builders seldom build poured crowns due to the added time and expense involved.

I read that, but don’t understand it, Marcel. That article talks about "holes in the brick or mortar. In this damaged brick, there is a plane of weakness parallel to the face of the brick, located about 1/4 " in from the face, along which the face separates. But no holes.

How about this:

Brick is a reservoir cladding. It rains all morning, water soaks into the brick for a certain distance, maybe 1/4"-3/8" and then it stops raining. The brick starts to dry from the outside, but when the outside is dry, there’s still a thin layer of wet brick 1/4"-3/8" back from the brick face. The sun goes down, the temperature drops below freezing and the moisture along that thin layer turns to ice and expands, causing the brick facing to delaminate. The bricks are from different clay deposits or different firings, so there are small differences in performance characteristics that cause them to age at slightly different rates and some will delaminate sooner that others. Kind of like batch problems in asphalt shingles.

The problem with this theory is that there’s efflorescence visible on the remaining brick indicating that the moisture came from inside the chimney. So maybe unlined chimney is the problem combined with brick batch variations.

Moisture is absorbed into brick and mortar, and with the temperature fluctuations the water expands and contracts. If brick and mortar were equally strong, this thermal expansion would cause irreparable damage to brick and mortar.

For this reason, the compression strength of mortar is less than the brick. As temperatures fluctuate, the expanding brick overpowers the expanding mortar. Over years of thermal expansion cycles, this will cause enough damage to the mortar that it will need to be repaired. If mortar wasn’t calculated to be softer than bricks, regular reconstruction of your masonry would be necessary.

Spalled bricks are primarily caused when mortar with an incorrect compression rate is used. Mortar is made to absorb the expansion of brick during freeze and thaw cycles. If the mortar is stronger than the brick, however, this role reverses. As brick isn’t meant to be squeezed by expanding materials, it can quickly deteriorate.

It is also possible, judging from your original photo, that the chimney had been re-pointed in the past 60 + years and a high compression strength mortar was used.

Type N should be used for chimneys.

Type M — The strongest (Highest PSI @ 2500) of the group, this type is most commonly used for load bearing walls and below grade applications, such as foundations or retaining walls. The Recipe: 3 parts Portland, 1 part lime and 12 parts sand. The low concentration of lime helps to achieve this high strength, but takes away from bonding ability. (A poor choice for tuckpointing anything.)

Type S — Also strong, @ 1800 PSI, Type S is most commonly used for laying. The Recipe: 2 parts Portland, 1 part lime and 9 parts sand. Because of it’s increased amount of lime, it offers the most flexibility in use and resistance to movement and weather.

Type N — A common mix for tuckpointing, and laying softer materials, Type N is the most flexible and resilient @ 750 PSI. The recipe: 1 part Portland, 1 part lime and 6 parts sand. Furthering the concentration of lime in the mix does take away from the structural strength aspects, but in turn offers more resilience and flexibility. Perfect for tuckpointing most exterior walls and chimneys.

Type O — At 350 PSI, this is the lowest strength mortar available in pre-mix. With the lots or lime, The recipe is: 1 part Portland, 2 parts lime and 9 parts sand. Not often used outdoors, Type O’s uses are limited to non load bearing walls and is generally an interior only used mix.

Type K — Abandoned for most practical uses, before I entered the trade, Type K is the least seen or used. Type K mortar is generally used only for interior or historical pointing of soft, hand-made brick. I’ve only made it once for curiosity’s sake only. (It’s a sticky mess.) Type K mortar has the lowest compressive strength @ 75 PSI., The recipe: 1 part Portland, 3 parts lime, and 10 parts sand. The increased porosity of this mortar can help protect movement of material it surrounds.

I sensing there are a lot of issues when you live in a snow zone… I would think that snow loads are also a big consideration on decks, roofs and run off during spring melts.

Efflorescence is salt, moisture is drawn to salt to balance or re-establish equilibrium to dilute the salt. As water evaporates it leaves more salt (efflorescence) on the outside, hence the cycle of hydrostatic pressure and sub-florescence which is deeper in the pores of the brick and mortar. So if the pressure is greater than the brick can stand and as in Marcels article and like I said look at your photos the mortar looks pretty good. One thing to note porous building materials in contact with the earth will pull the salt in and up and can travel a very long way, 6 miles by (hydrostatic pressure / osmosis). This will evaporate in the easiest place, if the chimney is encased in the home or painted then this would be the easiest place.

One thing to note as with Marcels post on mortar, this is why it is very important to use a strong lime based mortar when tuck pointing rock foundations or rock wall homes.

it’s not just now failing…the failure depicted has been an on going process since day 1
another possible is differing differing damage is fireplace usage

two good articles for masonry deficiency conditions