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Pipes, not ghosts, cause spooky noises

Published Aug. 27, 2005

Question: Our new home is now three years old. Ever since move-in day, we have had annoying ticking noises in several interior walls. Some of the noises start minutes after our furnace comes on. The clicks go away five minutes after the furnace shuts off. We have cracking noises when someone takes a bath or shower in a second-floor bathroom.

The builder says all this is normal, and nothing can be done. We never had this problem before. What is going on, and how can we stop these annoying noises?

Answer: You are a victim of simple expansion and contraction. The ticking, clicking and cracking are caused when metal ducting and pipes and plastic drain lines rub against the wood framing. These pipes and ducts expand as they are heated by the warm air and water that pass through them.

The expansion is perfectly normal, but the associated noise isn't. At first blush, it appears your builder might be guilty of a half-truth.

There could be many reasons why your previous homes were quiet. Maybe the plumbing drain lines were cast iron and experienced very little movement when hot water passed through them. Or the heating system may have been different.

Another possibility is that the installers who worked on your old homes were more experienced.

Craftsmen who know that metal ducts and PVC plumbing lines move can do things to make sure that movement happens with little or no noise. The trick is to isolate the pipes as much as possible from wood framing. The large trunk heating duct is often suspended an inch from the bottom of the floor joists so it does not touch the wood framing. Expansion joint collars often separate the large trunk heating duct from the furnace's extended plenum metal. These collars absorb an enormous amount of the expansion and contraction that happen just above the furnace heat exchanger.

Experienced heating and plumbing mechanics know to create slightly enlarged holes for ducts and pipes to pass through. They make sure a pipe can move freely as it passes through studs or framing members. If the pipe gets into a bind before it is heated and expands, it will most certainly snap, crackle and pop when it starts to grow after being heated.

PVC plumbing drain lines are notorious noisemakers. Plastic has an enormous expansion-contraction coefficient. The material grows dramatically and will crack and pop if it rubs against anything. If allowed to move freely, the PVC pipe will make no noise. But the pain is twofold, as you know. Once the hot water stops flowing through the pipe, the PVC begins to cool and contract. It makes the same cracking noise as it shrinks back to its original size. Metal heating ducts suffer the same fate as they contract.

Exorcizing these demons from your walls is not going to be easy. You will need to isolate and identify the trouble areas. This almost always involves removing the drywall or plaster. You can then often clearly hear and see the location where a pipe or duct might be rubbing against a wood framing member. The contact zone will need to be enlarged so that an air gap exists for the pipe or duct to move freely.

Do not cut away wood or enlarge holes in joists or studs. There are strict limits to the notches and holes that can be made in framing members. You can compromise the structural integrity of your home if you remove necessary wood. If in doubt, contact your local building inspector. Many inspection agencies will gladly advise you on what you can and can't cut. They do not want you or a family member to become a statistic.

Tim Carter is a licensed contractor. Got a question for him? Call from 6 to 7 a.m. today at (513) 749-1035 on his radio call-in show on WGRR-FM 103.5 in Cincinnati. You can listen to his archived radio shows online at any time by clicking on To view previous columns or tap into his archive of information and sources of building materials, visit Ask the Builder on the Web at