brick veneer cracks

[PSUengineer1]

Back elevation of house is brick veneer (about 30 feet wide). X-shaped crack pattern in mortar joints above back slider, with some vertical cracks in brick itself (see right side of photo 2). Lateral horizontal offset up to ~1/2" at corner. Do you agree that this movement in the brick is due to thermal horizontal expansion and contraction, AND NOT SETTLEMENT? There is no vertical joint in the brick over the ~30 foot length of the elevation. House is about 50 years old. See attached pics. Thanks.

 

[JoelTXCive]

That is a large expanse of brick without any expansion joints which supports your thesis of thermal expansion & contraction.

With that being said, those are some large cracks that have opened up, which might indicate some movement of the underlying structure.

What type of foundation is under the house? Is it a slab? If so, perhaps the corners of the slab are curling up/down as the moisture changes around the perimeter. For example, it rains for a day or two and the ground around the perimeter swells, then it shrinks as it dries out.

Also, is there any sort of bond break between the bottom bricks and whatever the bricks are bearing on? In Texas, the bottom course of bricks sit on 6 mil plastic which (in theory) allows a little bit of differential movement between the slab and bricks.

 

[hokie66]

No, I don't agree. Brick growth could be part of it, but I think you have some settlement in that right corner. Lintel corrosion could also be contributing.

 

[tolchijb]

Based on what I could see I think you have expansion/contraction issues where the brick band above the slider is continuous and the brick to the right of the slider is a relatively short length of masonry. This causes larger expansion/contraction forces in the upper plane than in the brick to the right of the slider. This caused the brick above the slider to push the corner outward. Note the right corner; the upper brick is pushed out relative to the lower brick. Beyond that I would believe there is some seasonal up and down at the right corner. The X pattern leads me to believe there is some reversal of load/movement happening. Check to see how well that concrete patio is sloped away from the foundation. All too often I see those settle near the foundation due to poor compaction and then water drains between the foundation and the patio slab.

 

[PSUengineer1]

The near 45-degree angle crack patterns above the slider tell me that the dead weight of masonry carried by the lintel is the weight of masonry enclosed within a triangular area of design (in other words, lintel was designed assuming arching outside of the 45). Agree?

 

[hokie66]

The crack pattern doesn't tell you how the lintel was designed, but does indicate how it is working now. Is the lintel deflecting?

 

[PSUengineer1]

@hokie66. Yes, a small amount of deflection was measured in lintel.

 

[PSUengineer1]

@hokie66: what you are saying is that the 45-degree lines extending from the ends of the lintel are indicative of lintel deflection. correct?

 

[JoelTXCive]

Here is a lintel size table. Maybe the lintel above the slider is undersized, or maybe it is not bolted? I think there is more going on than just a lintel issue though.

 

[dik]

For the location of the openings, you should have 2 or 3 vertical control joints. What type of foundation? What type of soil? Any significant changes in weather? Dryer? Wetter?

Dik

 

[hokie66]

Joel,
I agree it is probably not just the lintel, but on a wall like that, and in a 50 year old house, lintel corrosion is often an issue. The products of corrosion are much larger than the steel, so create large forces.

Don't understand what you mean by the lintel being bolted. I take it as a loose lintel.

 

[oldestguy]

Pretty much due to temperature expansion and the effect of openings dictating where cracks form. Lower right part of wall looks to be fixed due to fill, etc. explaining the crack going past that fixed section. Solution probably requires installing vertical joint roughly in middle, using openings as part of the "expansion joint." Thereafter repair all existing cracks. Even if no cracks in the peak section extend the new expansion joint up to the peak. At the foundation dig down a few feet and saw cut a weakened zone for the expansion joint there. Also remove and replace any rigid backfill at the right side to allow movement there.

 

[JoelTXCive]

Hokie-

On current brick facades in Texas, the longer span lintels usually get bolted to the wood frame header. Typically you see this at 2-car garage door openings where you have a 16ft-18ft spans. I believe the common practice is 1/2" lags with a 2ft spacing. I have also seen bolted lintels on spans above sliding doors if they were more than 6ft.

Although I have never seen an engineering analysis on it, I think the bolts allow enough load to shift off the lintel to prevent significant deflection and subsequent cracking. In my pre-engineering days, I worked for a large Texas homebuilder. Unbolted lintels above garages were a common warranty item and a real pain to fix because you had to tear out the brick to fix. Usually you then ran into color matching issues with the homeowner, which was a losing battle.

Anyway, I doubt the lintels were bolted on a 50 year old house, so that could be contributor to the cracking problem on the subject property. Personally my thought on the subject property is that there is some expansion and contraction going on combined with some seasonal slab/support movement.

Here's a photo from a house I built a few years ago. I don't know who the mason is, but he's proud of the bolted lintel! You can also see the poly they put down as a bond break in the photo too.

 

[dhengr]

PSUengineer1:
I agree with Hokie. Some of this has already been said or implied above, and I might just be saying it in slightly different words. The crack pattern shows how it is working now, not necessarily how it was designed. If the sliding door is working well, the lintel most likely is not the problem. What you really meant to say is the brick tends to act in an arching fashion over a lintel, with any lintel deflection and the cracking pattern shows that. But for the arching action to really work correctly and not cause the cracking you see, there must be a strong ability to impart arch supporting inward thrusts at the spring line of the arch (the head of the door opening elev.). The brick plane (or panel) on the left of the opening is stronger (stiffer) in this respect, than the shorter plane of the right. So, these thrusts tend to push things to the right. Then, you have the fact that brick is a naturally expansive material with age, and the more so with any water getting into the brick from (around) the window opening above. You could also have some thermal expansion, again pushing to the right due to that area being the weaker reaction plane. Finally, there could be some found. movement on the right corner. It is really good/helpful if you can watch these kinds of problems over a year’s worth of seasons, and if you can see them develop, rather than having them so well developed, that you are to late to see what caused what.

 

[nonplussed]

I tend to disagree that this has to do with just the lintel. That does not explain the extensive cracking on the right side. My best bet is that on the right side of the sliding door there is a sump or collection of water on the ground causing settlement of the footing there. You can see the ground slopes down towards the right, though I'm not sure if that's just the curvature of the photo.

I would continue to measure the cracks in different seasons during the next 1 to 2 years to see if there's seasonal variation. If no seasonal variation then I think the cracks are most likely thermal changes, although I'm not sure expansion of the brick explains the diagonal cracking above the opening; expansion should lead to cracks forming in the return wall on the right as the wall pushes outwards, so confirm if theres vertical cracking in the return.

Being a 50 year old building I would just tell the builder to repoint and live with it. Life isn't perfect and they can't expect an old building to behave brand new.