Drywall Cracks – Q & A

I am seeing suspicious cracks in my drywall.  What is causing this?

Your house is framed in solid wood and finished with drywall on the inside.  Most construction grade lumber is either surfaced dried (S-Dry) or kiln dried (K-D).  Wood with these labels tell you the wood was dried at the mill to a moisture content (MC) of no greater than 19%.  Ideally the MC will remain at 19% or lower.  During construction, piles of lumber sit open in the weather and get rained on or left directly on the ground and absorb excess moisture.  This causes the seasoned lumber to swell.  Just ask anyone who frames for a living if they have ever worked with waterlogged wood.  Most homes have some oversaturated pieces mixed in with the rest of the lumber.

Once the house is framed, it is closed in with sheathing, windows, doors, siding and roofing.  It begins a process called “drying in”.  This is when all construction lumber will begin to balance with the surroundings to achieve a stable equilibrium MC, usually around 8-14%.  This can take up to a year in a climate-controlled home.  The waterlogged pieces can twist, warp, shrink, and even crack.  Ideally, the affected pieces can now be replaced before installing drywall on the inside.  But your builder is carrying the costs of the home until it is sold to you.  What do you think happens?

The drywall goes up as soon as the inspection is done for the mechanicals and insulation.  The lumber dries out slowly.  In one to three years, it will finally be dry and many of the high MC pieces will begin to rear their ugly head.  Nails and screws will let go at high stress points and the drywall will hang free in those areas.  Lean against the wall and pop goes little circles of joint compound.  This is the least of the possible damage.  Excess shrinkage and warping will bow walls in and out, buckle drywall butt seams, and rip corner seams wide open.  Random diagonal cracks will appear over windows and doors.  Floors will squeak, doors won’t close and rarely, severe structural damage could occur.

Even if a home was framed with seasoned, sound framing lumber, damage could still occur from roof and window leaks or repeated flooding.  If your home is older than three years and suddenly starts to have drywall issues in an isolated area, check for leaks.  Wet lumber is more than just a cosmetic problem.  It could also be the starting point for a mold issue. (See mold question).

Fortunately, during our remodel, kiln dried wood is used and warped studs are replaced, sistered, or power planed flat.  We make a careful visual inspection with a level before the new drywall goes up.  This is why it is so important to have a good foundation anywhere in the structure.  It is important to do the job right the first time and get the walls precise.  This makes a huge difference around the tub or shower area to prevent the tile and grout from cracking in the future.