Plumbing Wall Thickness – Pipe Materials and Dimensions

Plumbing walls are the walls that have plumbing in them. That can be pipes or other plumbing fixtures in the bathroom, toilet, kitchen, or other parts of the house. Also called wet walls, plumbing walls need to be the right thickness to provide space for pipes and still support the weight of the house. 

Plumbing walls have a standard thickness of 6 inches. Plastic pipes use a wall thickness of 4 inches because metal pipes are often thicker than plastic ones. Cast iron plumbing requires a plumbing wall thickness of 4 5/8 inches since it’s thicker than plastic but thinner than other metal pipes.

Plumbing Wall Thickness

What are plumbing walls?

Plumbing walls are walls with plumbing fixtures in them. The plumbing, in this case, refers to pipes and other fixtures that go through the walls and emerge on fixtures such as sinks, toilets, showers, and others. 

Plumbing walls are often made to be stronger and thicker than the rest of the walls to maintain the integrity of the wall against the weight of the building. They’re also mold-resistant to prevent mold from growing inside the walls of the house. These walls, therefore, allow you to have pipes and other fixtures hidden from sight but without compromising on the strength of the wall. Over the plumbing walls you can have other materials such as quartz shower walls.

Plumbing wall thickness

The standard thickness of a plumbing wall is 6 inches. To achieve this, 2 x 6 inch wooden studs are used. These studs are 2 inches thick and 6 inches wide. As such, the distance between the walls is 6 inches. This is large enough to accommodate both metal and plastic pipes. 

2 x 6 inch studs are used since they’re strong enough to bear the weight of the building and still allow pipes to go through the wall. Even when holes are made through the studs for the pipes and fixtures, they will still be strong enough to carry the weight of the building. 

The rest of the walls (those without plumbing) can be thinner or as thick as the plumbing walls. This depends on the building laws and the age of the house with older houses having thicker walls (at 6 inches) than newer houses. 

Standard plumbingPlumbing wall thickness (inches)
Standard plumbing6 (2×6 studs)
Cast iron plumbing4 5/8 (2×4 5/8 studs)
Plastic plumbing4 (2×4 studs)

Wall studs are placed 16 to 24 inches along the wall and are measured from the top to bottom in the center of the stud. 

Metal pipes

Metal pipes are thicker and heavier than plastic pipes and require the plumbing walls to be 6 inches thick. Building codes also require that plumbing walls with metal pipes be 6 inches thick to accommodate the plumbing pipes and other fixtures. 

Metal pipes are found in the plumbing walls for most old buildings which were built when metal pipes were the standard. They can be replaced with plastic pipes which take up less space. However, the main sewer pipe is always made of metal. 

Plastic pipes

Plastic pipes, such as those made of PVC, take up less space than metal pipes and plumbing walls with plastic pipes are 4 inches thick. In this case, the studs used are 2 x 4 inches. While they’re 2 inches less in width than the wooden studs used in plumbing walls with metal pipes they’re still strong enough to support the weight of the building. 

Having plumbing walls that are 4 inches wide doesn’t affect the other fixtures in the wall such as electricity and internet cables since they’re all thinner than 4 inches. Newer houses have thinner plumbing walls due to the increase in the use of plastic pipes in walls compared to metal ones. 

Whether you’re using metal or plastic pipes, they need to have a thickness of 0.025 inches if they’ll be passing through the plumbing wall. This ensures that they don’t bust under pressure or start leaking to damage the walls of the building. When you fix a hole in a shower wall and there are plumbing fixtures in it, be careful not to damage them.

Wall thickness

Besides the studs in plumbing walls, you need drywall or other materials such as Corian shower walls on either side of the wall. Drywall for interior walls is ½ inch which adds 1 inch of thickness to the wall. For example, 2×6 studs inside a wall will result in a wall that is 6½ to 7 inches in total thickness. 2×4 studs will have a wall that is 4½ to 5 inches in total thickness. 

An interior wall needs to be at least 4 inches thick whether it has pipes and fixtures in it or not. If it has fixtures in it such as pipes and sinks, its thickness can range from 4 inches all the way to 12 inches with the standard plumbing wall being 6 inches. 8-inch walls are also common as plumbing walls. 

Exterior walls, on the other hand, should be 10 to 12 inches thick. The maximum thickness for a 70-foot wall (height) is 12 inches. For every additional 70 feet upwards, add 4 inches of thickness to the wall.

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