Cracking in Stucco
By John R. Schneider
Oct 5, 2002, 00:33
For the past two years Iíve
noticed small hairline cracks forming in the exterior stucco and in some of the
walls and ceilings of the interior rooms. At first I wasnít concerned, but the
cracking seems to be getting worse. Some of the cracks run up the corners of
walls and are 1/4 inch wide. The house
is only 5 years old and on a fairly level lot.
How do you tell if the cracks are normal or if they are something to be
concerned about? Does this have something to do with the foundation or soil?
Someone told me the soil around here has adobe in it.
B. P., Dublin
Hairline cracking to
interior and exterior surfaces of a building is very common, particularly in
wood framed construction, and is usually the result of building movement or
building settlement. Buildings have a
tendency to move because they are subject to the forces of nature and ground
movement, as well as the effects of expansion and contraction of the framing
system and finished surfaces.
If you think about it, a
house is only as stable as the ground that supports it. Houses built on adobe soil will experience
more movement than most homes because of adobeís great potential for expansion
and contraction. Most of the soil here
in the Bay Area has some adobe content, and when this soil moves, vibrates or
settles, so does the house that sits on it.
The catalyst for adobeís ability to expand and contract, is moisture.
During the winter months
when adobe soil gets wet, it expands.
During the spring and summer as the rains begin to stop and the soil
starts to dry out, the adobe actually contracts and shrinks. This movement of adobe soil is the biggest
contributing factor to hairline cracking in the surfaces of a building.
Cracking in stucco and
sheet rock most commonly occurs at the outside corners of window and door
openings, the inside corners of walls and ceilings and sometimes at joints in
the finished surfaces. This is usually where building movement is most evident.
Most of the time, minor cracking at these locations is not a structural
concern, and is considered to be
cosmetic. However, large or progressive
cracking can be an indication of a structural compromise.
With the winter and spring
rains and long dry summers we have had the past two years, the soil has had the
opportunity to move more than normal.
This can make hairline cracks become bigger and more noticeable, and can
cause doors and windows to shift and bind in their openings. This may be what you are experiencing with
Normally, it is during the
summer months that cracks in stucco and sheetrock become seem to occur. This is when the soil under the house is the
driest, and most compact. Often these
cracks are not new cracks, but existing cracks that have merely opened up and
are now move visible to the eye.
So how can you tell if
cracking is serious? A basic rule of
thumb suggests that a crack is cosmetic if it is less than 1/8th of an inch
wide, and if the edges of the crack still line up with one another. Take a look at one of the cracks you are
concerned about. If you look at the
edges on either side of the crack, and the edges still line up (if you were
able to push the crack back together), then the crack is considered minor and
On the other hand, if the
crack is more than ľ of an inch wide, and edges of the crack have shifted or
moved in relation to each other, the crack is considered to be serious. It is the shifting or slippage of the opposite
edges of the crack that often indicates unusual movement of the components of
the house. This shifting can be an up or
down movement of the edges, a shifting that causes one surface to rise above
the other, or a tilting of the surfaces so that the crack is wide at the top
and tight at the bottom.
Large cracks and cracks
that have shifted, indicate that some part of the framing system and /or the
foundation, has moved and created enough stress for the surface materials to
break apart. If the foundation on one
side of the house has settled more than the other side, cracking will occur.
Cracking will also occur when a vertical support post under the house settles
or moves. Large cracks should always be
investigated to determine the cause before any repairs are attempted.If the cracking is minor,
the crack can be usually be caulked and painted over.
Ideally, the crack would be
cut open slightly, to allow the caulking or patching material to fully seal the
void between the two edges. Otherwise,
the caulking will only be on the surface of the material, and will separate or
break apart whenever the crack moves in the future.
John R. Schneider is a
licensed general building contractor and a certified residential code
specialist. He is president of All About Homes, a residential inspection
company, and has been performing code and construction consultations since
1985. Readers may address their comments
to John Schneider, 24326 Mission
Blvd. Suite 7, Hayward,
Ca 94544. Fax number: 510 537-8666, or
on the web at www.allabouthomes.com.
Please include your phone number.
Schneider will answer questions of general interest in the paper. He
reserves the right to edit the letter for brevity and clarity. Readers are
encouraged to contact a competent contractor or code consultant for specific
information regarding questions they may have about their homes.
Copyright 2002, John R.
Schneider, all rights reserved
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