Hot water entering the pipes heats the metal and causes the pipes themselves to expand, sometimes significantly. When passing through tight spaces in walls and floors, a pipe that expands even slightly will rub against wood. This can result in strange sounds such as clicks, squeaks or knocks, depending on the exact acoustics. According to Herald Tribune, cutting the wood in the area where it impacts the pipe is a simple solution. Pipes pass through tight spaces in many places without causing a problem, and giving these trouble spots ample space will go a long way in eradicating your noise problems.
In order to cut material close to the pipe, a hacksaw may work, but for working in tight spaces, the pointed end and precise drilling of a keyhole saw is probably the best option, note home repair geek. Before making any cuts, however, you must ensure that the pipe itself will be fully supported after removing the material causing the chafing. According to Genesee Valley Penny Saverthe pipe should not move more than an inch in any direction as you work – any significant change can damage the seals, which would be a much more annoying and expensive problem.