How Thick Is An External Wall?

Whether you're building a home from the ground up or adding on to your existing home, knowing about the standard thickness of exterior walls is a must. Too thick, and you're wasting valuable material and space; too thin, and your dwelling will be allowing the heating/cooling to escape, and will also not be able to support the structure's siding and roof. So, how thick should an external wall be? We did the research to bring you the answer.

External walls are generally 10 to 12 inches wide. Homes that are built with rammed earth or heavy exterior masonry will have thicker walls. There is no limit to how thick an exterior wall can be. Rather, most of the thickness will be determined by the framing itself, then the siding material will be tacked on for the final measurement. 

Now that we have established the recommended thickness is for an external wall, we will look further into walls in general. You might also be wondering what exterior walls are made of, or why exterior walls are thicker than interior walls. To get the answers to these questions and more, just keep reading!

These modern houses incorporate a number of contemporary elements, such as overlapping roofs that slope in just one direction - parallel to each other, hardwood timber cladding, and large, single rectangular windows, with imposing grey aluminium window frames, How Thick Is An External Wall?

What Constitutes A Wall?

A wall is any structure that is intended to divide or enclose a measured space. Walls can be interior, dividing rooms on the inside of a building, or they can be on the outside. We'll look at what defines an exterior wall shortly.

If you're building a new wall or extending an existing one, you'll want to be sure that certain building guidelines are met. Thankfully, the framing of a wall and the drywall that covers it will almost always meet the requirements for thickness. 

What Is Considered An Exterior Wall?

With all of this discussion about exterior walls, it's only fitting to discuss what constitutes an exterior wall. In general, an exterior wall is any wall that forms part of a building's envelope. It must be all or partially on the outside of the structure, with roof supports attached to its top.

What Are Exterior House Walls Made Of?

As you can probably imagine, exterior walls can be constructed from a wide variety of materials. Here, we'll examine some of the most commonly used types, so that you can get a better idea of what you might be inclined to use on your own projects.


Street light's shadow cast upon aluminium cladding

This type of exterior wall is most commonly used for buildings that are in need of an outside rehab. This premade wooden material is affixed to the outside frame of the building, giving it a needed facelift. 


Photo of a small American red brick home on a sunny day

Brick has been a popular external wall option for centuries. This option is great for adding additional insulation to a structure, as the bricks are thick enough to withstand extreme changes in outside temperatures.

Insulated Vinyl

Exterior wall of home with new blue vinyl siding and a vinyl insulated window

This type of material is the most commonly used on residential homes. The reason for its widespread usage is due to the lower cost, the longevity, and the relatively low maintenance on the material itself. 

Insulated vinyl is easily installed. It is affixed to the exterior frame of the structure quickly, and it helps the building retain much of the desired internal temperature.


Modern house exterior design with wood siding

Wooden siding can come in several types, all of which have their own advantages and disadvantages. Whether you're dealing with log, shiplap, or hardy plank, know that wood takes more skill and time to affix to the side of your building.

The lifespan of wooden siding will vary depending upon the type, the climate, and other factors. But with routine maintenance and repairs, most types of wood siding can last up to thirty years with minimal issues. 


Close-up detail of cottage house corner with metal planks siding and roof with steel gutter rain system

Steel has become a more popular option for external walls in recent years. The walls and siding are durable, strong, and require less maintenance than vinyl. While more expensive than most types of external walls, builders have begun to embrace this material because of its longevity. 

Cinder Block

Sturdy and stackable, cinder blocks are used for exterior walls for homes and commercial structures. These blocks are fairly thick, which will help insulate the building more than most options.

However, their thickness has a downside. The thicker the wall, the more likely moisture will accumulate inside of it. Moisture inside an exterior wall can eventually lead to mold and mildew problems as well as contribute to the slow deterioration of the wall itself. 

Why Are Exterior Walls Thicker Than Interior Walls?

If you've read this post in its entirety, you've noticed that interior walls are not nearly as thick as their exterior counterparts. Why is this?

Exterior walls are thicker for both structural and insulation reasons. Let's take a look at each, so you'll get a better understanding.

The siding material and inside drywall will only allow a home to maintain so much of its desired internal climate. Cold weather can pierce even the best quality vinyl or wood siding, and they aren't any match for hot weather days.

The extra thickness allows for there to be a great deal of needed insulation. When installed, this material helps keep external temperatures from affecting the inside of a home. Likewise, good insulation also keeps the desired climate inside the walls to be more constant.

External walls need to be made thicker to support the structure it encloses. The bulk of the dispersed weight of the structure's roof is placed on the outside walls, so making them thicker will lend much more structural support.

In Closing

Making certain that your home's exterior walls have the proper thickness is important for the safety of the building. The additional thickness also allows for needed insulation to be installed, so that the building is able to maintain the desired temperature without placing too much strain on the heating and cooling systems. 

Before you go, be sure to check out these other guides that might be of interest:

How Long Should Exterior Paint Job Last

11 Awesome Exterior Wood Siding Ideas

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