3D Printed House Cost
3D Printed House Cost - It's Not All Unicorns and Rainbows
You may wonder if the new belle of the ball, 3D printed house, is really going to cost you less money to build than a normal house. Some publications fawn about new techniques like these and only share the glitter and gleam of the technology. This is nothing new as decades ago lots of bold promises were made about geodesic dome houses and A-frames. Both were flash-in-the-pan trends and only time will tell what will happen with 3D printed homes.
I prefer to roll up my sleeves and deal in reality when it comes to what a 3D printed house cost might be. Let's unpack what's in play.
What's Really Different About a 3D Printed House?
The only thing that's different about a basic 3D printed house vs. one built with lumber is the exterior walls. You can build a 3D printed house where all the walls are made with the concrete batter that oozes out of the machine nozzle, but for sake of this column, let's just consider the exterior walls.
A concrete mortar created with sand and Portland cement is extruded through a moving nozzle. Layer after layer of this mortar is placed precisely by a computer-controlled machine. The resulting wall takes the place of a traditional wood-framed wall that could have been built in a factory using similar precision technology.
Keep in mind that a traditional single-story house built with wood wall panels made in a factory can be ready for the roof in less than one day. I'm talking about comparing apples to apples with a 3D-printed house. Let's assume any square footage less than 2,000 square feet for sake of discussion. So don't get wowed when the 3D printed house folks tell you it's a huge time saver.
Other than that, everything else in the house is pretty much the same as a normal frame house. Watch this short video to understand the technology:
What are the Drawbacks of a 3D Printed House?
There are lots of drawbacks or hidden bugaboos with 3D printed homes. Almost all of these factor into the cost of the 3D printed home and some may actually cause the price of the home to go up. The following questions are ones you should be thinking about asking a 3D house builder.
The following is not a complete list of drawbacks or questions you might ask. These are just a few of the major ones that are tumbling around in my tiny gray cells as I write this column.
Mobilizing the Giant 3D Printer
Imagine what it costs to drive the giant machine to your job site, set it up, calibrate it, and then take it all apart once the job is complete. Are there any extra foundation or site requirements to ensure the machine is completely stable as it operates? Do you need to pay for a crane twice to lift it off then put it back on a flat-bed tractor-trailer?
Quality Control of the Mortar
How is the quality and integrity of the cement mortar controlled at the job site? Is this mixture created by workers on the site or brought from a ready-mix concrete plant? How do you know if the material has enough Portland cement in it?
The exterior walls are solid concrete. Masonry is a poor insulator and heat is sucked into cold masonry faster than water entering a sponge. How do you achieve a R-rating for exterior wall insulation that will meet or exceed the energy code recommendations? CLICK or TAP HERE for a table of exterior wall R-values for all USA states. Do you have to build a wood-frame wall inside the exterior wall and then add fiberglass? Do you glue closed-cell foam to the inside of the exterior walls?
Building In Cold Climates
The concrete mortar used to build 3D printed houses contains water. You can't allow this water in the oozing mortar coming out of the printer nozzle to freeze before it achieves a certain PSI strength. CLICK or TAP HERE to understand what's in play when working with concrete in cold weather. Yes, you can add anti-freeze chemicals to the mortar mix to help prevent freezing, but check into how these chemicals affect the long-term strength of the concrete mortar.
That said, what are the limitations of building a 3D printed house if the weather forecast for the day the printer is turned on is for a high of 20 F with a low temperature that night of -3 F? What extra costs are involved to prevent the wet mortar from freezing?
Installing Electric in Exterior Walls
How are electric outlets installed in exterior walls? The National Electrical Code is quite specific about the requirement of having outlets every 12 linear feet on walls in rooms. It's quite obvious the electric is added later after the 3D printer is moved to the next job site. How is the electric work done and what does it look like? Will it be the industrial look with metal conduit and boxes screwed to the exterior walls?
Plumbing on Exterior Walls
It's common to have a kitchen sink on an exterior wall centered on a window. How do you install the plumbing drain pipe and the required vent pipe in the 3D printed wall? Don't let the builder or plumber tell you they're going to use a modern air-admittance valve (AAV)! These mechanical devices with moving parts eventually fail allowing sewer gas to enter your kitchen. You don't want an AAV, believe me.
Many houses have a kitchen wall or two on an exterior wall so you can get natural light into the room. How are kitchen base and wall cabinets attached to the rough 3D printed concrete walls? How do you deal with countertop backsplashes on these exterior walls? What extra costs are involved dealing with the rough surfaces?
Interior Wall Surface
What is done is you don't like the look of the rough 3D printed concrete? How do you get a smooth interior wall? What does this cost?
Exterior Wall Surface
Most of the 3D printed homes I see the exterior concrete layers are just painted. What happens if you don't like this look? What if you want a brick, stone, wood, vinyl, or other exterior surfaces that might appeal more to your tastes?
Don't fall for the sizzling sales talk when it comes to 3D printed home cost. Use your own tiny gray cells and imagine other questions that you might want to ask before you decide this is the path to take.
This column was featured in the July 4, 2021 AsktheBuilder Newsletter.