Drywall is a building substrate well known for its ease of use, low cost, and overall durability. It offers a fantastic price-to-quality and price-to-safety ratio. As a result, it is used widely in nearly every type of building construction project to create a clean finished interior quickly, achieve fire rating, and to provide custom interior upgrades for less than wood carpentry.
Of course, drywall is effective as a time and money saving option only if the installation is executed well. Mistakes or lack of foresight during installation may result in costly repairs over time. Stresses like temperature, moisture, and settling, can lead to cracks in the drywall that require repair. Avoid the call from the unhappy client asking you to come back a few weeks after completing a job to do repairs. With proper installation, these pitfalls can be avoided. Preventing cracks proactively alleviates the risks associated with repairs that can affect your bottom line.
What is even more costly to the drywall contractor are the indirect expenses – losing customers or tarnishing a good reputation - making it more difficult to obtain jobs in the future. As an example, consider the following: drywall installed in the summer may crack due to environmental fluctuations in the winter. In these cases, you might not be called to do free or reduced-cost repairs (as when the cracking occurs immediately) because you might not be called at all. A client who sees cracking many months after the job was finished may conclude that the drywall was installed poorly to begin with. In such a case, the customer will probably call someone else to do the repairs.
As you can see, avoidable repairs, even cosmetic ones, are costly because not only does the contractor lose the potential for repeat business from their customer, but they lose the high value of a referral. A dissatisfied client is likely to tell others about their bad experience, via word of mouth or through online reviews. For this reason, understanding the sources of cracking and how they can be avoided is crucial to building and growing a successful drywall business.
Causes and Types of Cracking
Cracks can form for a variety of different reasons. Depending on the location of the crack, it may be caused by building movement, environmental factors, or lack of foresight on the part of the professional who installed it. In the following sections, we’ll break down everything you need to know about cracking based on the location of the crack (ceilings vs walls) then explore possible causes as well as solutions. Jump to the section you need or read on to get an overview of the various causes of drywall cracking to identify and plan around.
Many new and recently built structures use trusses – manufactured assemblies that transfer load to the outside walls, allowing an open interior with few, if any, load-bearing interior walls. While they are a great solution for modern design and often cheaper than stick built roof framing, trusses are subject to a particular problem called uplift. Uplift is were the bottom cord of the truss is subjected to significantly different environmental conditions (moisture/temperature) than the rest of the truss. When this happens, the bottom chords, buried in heavy insulation, stay dry and contract, while the rest of the truss assembly does not. In fact, the upper part of the truss may expand as it is exposed to high humidity. This causes an upward expansion that pulls the drywall up with it causing cracking at the interior ceiling corners.
Solution: Installation of truss clips or backing angle designed to minimize inside corner movement and thus prevent truss uplift.
Products like Trim-Tex Truss Backing Angle are installed along the length of the wall and hold the drywall inside corner together while allowing the trusses to move. The drywall should be attached to the truss 18" out from the backing angle to allow for movement without cracking.
Like truss uplift, building deflection results from movement of the building itself. Deflection can occur at the head of wall in any multi-story structure. Deflection is the result of joists, trusses, rafters, concrete decks etc. bending when overloaded.
Any building that occasionally takes an unexpected load or deals with widely variable loads should consider prevention measures to avoid cracking from deflection. Typically, caulk or a flexible gasket, such as Wall Mounted Deflection Bead, is installed that can compress under load, sparing the less flexible materials (like concrete and drywall) from having to bear the burden of building movement.
For more information on the effects of building movement on interior finishes, check out this free course.
Similar to the problem of truss uplift, vaults can crack when lumber shrinks on both sides of the peak, adding stress to the inside peak. Cracking can also result from improper application of joint compound in an inside corner angle. Fortunately, flexible vinyl beads can help protect against this type of cracking. Products like Magic Corner offer a flexible center channel, allowing for installation at any angle, and provide controlled movement up to as much as 3/8”.
You can simply papertape off angles, but off angles are prone to poor framing and hanging. A flexible roll product will create a straight crisp inside corner, hiding any imperfections beneath. There are many brands (No-Coat Ultra Flex, Strait Flex, Trim-Tex Angle Master) that feature a roll product designed for off-angle applications. They are engineered to flex to fit any off-angle corner. Some feature a paper flange while others are made of vinyl. A vinyl off-angle finishing solution such as Angle Master prevents you from having to worry about paper scuffing or blistering.
Just as in ceilings, walls can suffer from differential expansion in response to environmental concerns. As a result, in long runs of drywall (over 15ft) it is important to leave a gap between sheets to allow them to expand and contract freely to accommodate fluctuations in the ambient environment. However, these gaps must be bridged by expansion joints that control the movement and create a unified surface. The best expansion joints are made of vinyl, which resists denting and take advantage of the flexible properties of vinyl, limiting wear and tear and the need for repairs. Expansion control joints are even available in fire-rated versions, allowing you to meet code with minimum fuss and labor.
While it may seem obvious, it's worth mentioning that one of the leading causes of cracked drywall, especially in commercial and multi-family environments, is natural wear and tear. As clients come and go or tenants move in with all their possessions, it is easy for them to bump into a corner and leave it cracked or dented.
Traditional metal corner beads offer some protection against these kinds of impacts because they offer good tinsel strength. However, the downside of metal beads is that once deformed, they do not spring back, so any dents or damage will be permanent. Alternatively, vinyl corner beads offer similar resistance to damage, but are flexible and bounce back. This reduces the need for repairs as vinyl can deform temporarily in response to impact and then return to its original shape. Drywall subcontractor Drywall Nation demonstrates how metal bullnose is no match to the resilience of vinyl.
A second advantage of vinyl is the ease of manufacturing vinyl into various shapes, allowing vinyl beads to be produced in a variety of styles that make it particularly well-suited to luxury multi-family structures where a custom and homey feeling is desired.
Manufactured housing has to address all the same concerns of stick built housing, plus it must concern itself with the safe transport of fabricated architecture to the site. What’s more, it has to meet its own set of codes regarding safety and construction standards. As a result, manufactured housing companies turn to vinyl as high quality inexpensive material, and a long-term solution. Learn how vinyl products solve the challenges of drywall finishing manufactured housing.
Against Building Substrates
Adding to the complexity of solving problems related to building movement – especially expansion – is the fact that materials expand and contract at every single edge, including internal ones. That means that there is also the potential for expansion (and cracking!) at any place where different materials meet: doors, windows, and wherever drywall meets concrete.
For these cases, you should consider products that not only seal against the environment, but offer the flexibility required to keep doors, windows, etc. functioning correctly and with no unsightly cracking around the edges. Where the drywall meets the window and door frame in this image, Super Seal Tearaway should be used to create a clean finished edge that offers protection for the drywall as well as a seal.
Surface & Edge Cracks
Beyond the many environmental factors (like building movement) that contribute to cracking drywall, they are plenty of factors that relate to the correct installation and finishing of the drywall surface. For instance, one very common cause of cracking is applying drywall mud too thick. As the mud dries, the surface dries first. When the mud is too thick, the surface hardens while the material below is still drying. This differential can result in cracking To avoid this problem use several thinner coats of compound.
You can also use powdered mixes/setting compound that dries using a chemical process rather than water-evaporation. As a result, it dries more quickly and shrinks less, making it less prone to cracking. Be advised though, that the quick drying time makes it difficult to mud large projects evenly, since the mud may set before you’ve finished. A glue-like drywall mud additives such as Mud Max can be mixed into your mud of choice to make it more malleable when dried. This gives the mud more flexibility and allows the mud itself to move a bit in response to environmental factor. Glue-like additives can help limit cracking in the case of movement.
Butt joints - where two pieces of drywall meet, is an area susceptible to cracking. To minimize cracking do your best to place your butt joint where they are the least exposed to movement. For instance, notch your drywall around doors and windows instead of breaking drywall at these movement prone areas. Next, leave a 1/8" gap between your boards, do not fit them tight against each other. This 1/8" gap give the boards room to move. For your bedding tape coat choose Durabond or another general purpose compound (not lightweight), which will dry harder and contains more adhesive. Use paper tape or FibaFuse for your bedding coat instead of mesh. Mesh tape has the tendency to twist causing a crack to form.
Limiting the amount of mud needed to feather the butt joint also reduces the likelihood of cracking. As we discussed earlier, cracking often occurs when the mud on the surface dries faster than the mud underneath. Buttboard is a product that creates an easy to fill recess, similar to a factory edge. While it may look like a standard piece of OSB, the board is cut with a slight V that pulls in the drywall edges. See how Buttboard works. This recess requires less mud to fill then feathering a traditional butt joint that breaks on a stud, which often forms a hump that must be feathered.
Mud Leg Edges
There are a number of factors to be aware of in order to avoid hairline cracks where corner bead meets the drywall. First, never nail the corner bead into the framing. This will allow the framing and drywall to move independently from each other. Using a mesh or FibaFuse over the mud legs of a metal or vinyl bead reduces the amount of compound needed to create a smooth transition. It additionally increases the bond strength between the corner bead and drywall reducing the chances of a crack forming. Alternatively, using an adhesive mud additive such as Mud Max and thin even coats (never use Mud Max on the finishing coat), you reduce the chance of edge cracking without the need for mesh taping the legs.