Ask the Builder: Questions to Consider About a 3D Printed Home
You might be wondering if the new belle of the ball, a 3D printed house, is going to cost you less to build than a normal house in these times of stratospheric wood prices. Some publications are interested in new techniques like these and often only share the sparkle and sparkle of the technology.
This is nothing new, as decades ago many bold predictions were made about geodesic dome houses, A-frames and, more recently, straw bale houses. All were flash-in-the-pan trends, and only time will tell what will happen with 3D printed homes.
The only thing that differs from a basic 3D printed house versus a house built with wood are the exterior walls. You can build a 3D printed house where all the exterior and interior walls are made with the concrete paste oozing out of the machine nozzle, but for the sake of this column, let’s just consider the exterior walls.
A concrete mortar created with sand and Portland cement is extruded through a movable nozzle. Layer after layer of this mortar is placed with precision by a computer-controlled machine much like a pastry chef decorates a cake. The resulting solid masonry wall replaces a traditional wood-framed wall that could have been built in a factory using similar precision technology.
Keep in mind that a traditional one-story house built with precision factory-made wood wall panels can be roof-ready in less than a day. So don’t be fooled when the folks in the 3D printed home tell you it’s a huge time saver.
There can be many disadvantages or hidden bugaboos with 3D printed houses. Almost all of these factors affect the cost of the 3D printed house, and some could actually increase the price of the house. The following questions are the ones you should think about asking a 3D home builder. The list is far from complete.
Imagine what it costs to drive the giant 3D printing machine to your job site, set it up, calibrate it, and then take it apart when the job is done. Are there any additional foundation or site requirements to ensure the machine is completely stable when operating? Do you have to pay twice for a crane to lift it and then put it back on a flatbed semi-trailer? Is there enough room on the ground to place the machine. What must be the level of the ground?
The exterior walls are solid concrete. Masonry is a poor insulator, and heat is drawn into cold masonry faster than water entering a sponge. How do you get an R rating for exterior walls that will meet or exceed energy code recommendations?
Do you have to build a wood frame wall inside the exterior wall and then add fiberglass? Do you glue closed cell foam inside exterior walls?
The concrete mortar used to build 3D printed houses contains water. You cannot allow this water in the oozing mortar coming out of the printer nozzle to freeze until it reaches a certain PSI force.
Yes, you can add anti-freeze chemicals to the concrete mix to help prevent freezing, but check out how these chemicals affect the long term strength of your 3D printed wall.
How are electrical outlets installed in exterior walls? The National Electrical Code is quite specific on the requirement to have outlets every 12 linear feet on the walls of rooms.
Are exterior wall outlets added after moving the 3D printer to the next job site? How is electrical work done and what does it look like? Will it be the industrial look with metal ducts and casings screwed to the face of the printed walls?
It is common to have a kitchen sink on an exterior wall centered on a window. How to install the required plumbing drain pipe and vent pipe in the 3d printed wall? Don’t let the builder or plumber tell you they’re going to use a modern air intake valve. These mechanical devices with moving parts eventually fail, allowing sewer gas to enter your kitchen. You don’t want AAV, trust me.
Many homes have a kitchen wall or two on an exterior wall so that you can get natural light into the room. How are the kitchen base and wall cabinets attached to the 3D printed rough concrete walls?
How do you deal with the countertop backsplashes on those exterior walls? What are the additional costs associated with treating rough surfaces?
What if you don’t like the look of 3D printed raw concrete? How to get a smooth interior wall? What does it cost?
Most of the 3D printed houses I see have painted exterior walls. What if you don’t like this look? What if you wanted a brick, stone, wood, vinyl or other exterior surface that could suit your tastes more?
Be careful not to fall for the sizzling sales rhetoric when it comes to the costs of 3D printed homes. Use your own little gray cells and imagine other questions you might want to ask before you decide this is the way to go.
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