What Problems Come With Cheap ADU Kits?

By Buz Artiano, BuildX | February 2026

Unfortunately, we see this every week. Someone will call us excited about an ADU because they found a builder advertising modular units "starting at $110,000." The customer has done the math in their head and figured that even if the price doubles, they can still build an ADU for under $200,000.

They decide to go this route only to have reality hit later. After spending weeks or even months with that vendor, they discover the actual cost will be $300,000 to $400,000. The "$110,000" was just the two boxes delivered to the site, not set on any foundation, with no HVAC, no utility connections, no site work, no permitting, and no surveying included.

At BuildX, we have years of experience building ADUs in Massachusetts, but we have also taken apart enough modular structures over the years to know exactly what is behind the walls. What we saw and learned is the reason we take a totally different approach to construction and quality.

  

What Is Actually Excluded From Those Low Advertised Prices?

When a modular builder advertises pricing "starting at $110,000," that number typically covers only the prefabricated boxes delivered to your property. The price does not include setting them on any foundation or connecting utilities or anything else.

Here are the things that get left out of those advertised prices: foundation work, all site work which could include tree clearing and grading, permitting fees, surveying costs, HVAC system installation, and the connections required to set up permanent electrical, plumbing, and sewer services. Some electrical and plumbing can be done inside the boxes at the factory, but none of the connections to your home's utilities are included with that.

The result is that homeowners will see a $110,000 advertised price and assume they can complete the project for under $200,000, but the project really ends up costing $300,000 to $400,000. That is a significant price difference. It can end up being three to four times what they budget for.

Why Do Modular Builders Use This Pricing Strategy?

What we see from a lot of builders is what we would consider false advertising. These vendors have taken the low road by publishing incomplete pricing that takes people down a false pricing path.

The reason they get away with this is because it captures attention. A homeowner searching for ADU options sees "$110,000" and thinks this might actually work, even with an extra hundred thousand added to the price. By the time they spend weeks or months working with that vendor and realize what it really costs, they have already invested significant time and energy into that company and that can be very discouraging.

It always ends up being a waste of time for everybody sadly. The homeowner wastes time discovering the real numbers, the vendor wastes time with buyers who can't actually afford the project once all costs become transparent.

What Design Problems Show Up in Budget ADU Floor Plans?

Beyond the bait and switch pricing, cheap ADU kits often feature floor plans that are poorly thought out and do not maximize or utilize the available space well. We recently reviewed some floor plans from a modular builder during one of their webinars. They proudly displayed five or six plans on screen.

Not a single bathroom was the slightest bit accessible for an elderly person. On top of that, none of the bathrooms included any linen closet, cabinet, or storage whatsoever. Every bathroom was simply a shower, a toilet, and a small vanity.

When you get out of your own shower, you should have a towel ready within reach. There's no reason to have to bring a toiletry bag from your bedroom into your bathroom every time you shower like you are staying at a motel. In a brand new house, you should have your own storage for all your bathroom stuff.

At BuildX we refuse to entertain the idea of those awful cramped bathrooms. There is no linen closet, no storage, and the toilet is jammed right up against the tub or shower. That design approach dates back to the 1970s when small homes were selling for $20,000 and buyers had no other options. People do not need to live that way now.

The people who design those bathrooms should be embarrassed. Honestly, we have seen better bathrooms in low budget mobile homes.

Will a Cheap ADU Kit Last as Long as Site-Built Construction?

If you are on a tight budget and need a very basic ADU, there is nothing inherently wrong with going with a modular unit. It will cover the basics and meet minimum code requirements, and it can last 20 to 50 years. Which is all fine and great, but it will not be a 200 year structure. It will be designed to meet the absolute minimum legal requirements only.

In our experience, we have actually had to disassemble many modular homes over the years, and when we opened the walls to see what was behind there, let's just say we were not impressed. The main selling point for modular construction is that it is built in a factory, but that says nothing about the people who work there and their experience level.

When these homes fall apart in 10 to 15 years, do you think it was worth saving $40,000 upfront? Every homeowner should consider the answer to this before moving forward with their own project.

What Material Quality Issues Appear in Factory-Built ADUs?

Factory-built ADUs often use sub standard materials that are selected purely for their low cost. They are not made to last. Factories spray everything with glue. The structures are full of the cheapest OSB (which means Oriented Strand Board) available. These materials can actually off-gas, which can really become a problem for anyone with environmental sensitivities.

We had a client whose daughter has these types of sensitivities. The father originally called us about building a modular ADU, but once he explained his daughter's condition, we told him up front that we cannot build a modular house for this situation. We have no idea what they are going to do in the factory with spray glue, adhesives, and cheap OSB since we are not the ones building it. His daughter would never be able to live in that house and he could have potentially wasted hundreds of thousands of dollars.

Even if you try to specify certain materials or methods, you still can't control what a worker in a random factory does. That lack of oversight is one of the main issues with a factory build home.

Consider flooring as another example. We use a Mohawk brand luxury vinyl tile at $4.50 to $4.70 per square foot because it is American made, high quality, with high quality joints and a built-in pad. You do have the option of buying flooring at $1.69 per square foot from discount retailers, but when it gets cold and the material shrinks and all the locks pop, it won't be worth the $2000 you saved to begin with.

Why Does Off-Brand HVAC Equipment Create Long-Term Problems?

Cheap ADU builds often include cheap off-brand HVAC equipment so they can sell the unit for a lower price. We have seen heat pumps from brands we didn't even recognize be installed in budget builds.

There are tons of Chinese knockoff systems available for a lot cheaper than name-brand equipment like LG or Mitsubishi. There are multiple problems with these systems.

First, a lot of off-brand heat pumps only work down to 5 or 10 degrees. Name-brand systems operate down to minus 15. That difference matters during a very cold winter in Massachusetts. An off-brand system means you can't heat your house to comfort when it's especially cold outside.

Second, when the circuit board burns out or another component fails, you cannot find replacement parts and you have to buy a whole new system. You saved $3,000 on the original system, but now you have to rip the whole thing out because you can't get the parts to fix it. By this time, you haven't really saved any money, and the system doesn't work.

Don't get us wrong, even name-brand equipment breaks, but it can be fixed. Not too long ago we had a customer call about having no hot water. Our HVAC technician went right over, identified the problem, had the part on the truck, and had the system running again within half an hour. If they had an off brand system, it would have been thousands of dollars and a long waiting period for new equipment to be installed.

Don't forget that equipment never breaks when it is 60 degrees and sunny. It breaks during the coldest week of winter when you really need it.

Is There a Place for Budget ADU Construction?

We are not saying that there is something wrong with modular construction, as long as you understand what you are getting. You have to understand that it's a completely different product. In our opinion, based on taking many of them apart over the years, it is an inferior product. We only sell site-built construction, so you kinda have to take that for what it's worth.

If you just need a very basic, code-compliant structure on a tight budget and you understand the 20 to 50 year lifespan, a modular ADU may still work for you. The problem is if buyers are misled about the real costs or they don't understand the quality they are sacrificing.

Our best advice is that if you want the lowest bottom-line price, that is not going to be us. That's not who we are and it's not what we do. We build middle to high end products that will last your family several lifetimes, with zero maintenance on the outside and high-quality products on the inside.

If you want to understand what an ADU will actually cost on your property, including all the items those advertised prices leave out, we are happy to walk you through it and give you realistic numbers you can count on.

Making an Informed ADU Investment Decision

The difference between a $110,000 advertised price and a $350,000 actual project cost is huge. So is the difference between a 25-year structure and one that will outlast you and even your children.

When going over your ADU options, ask builders to include a detailed list of every cost required in order to get a legal certificate of occupancy. You also want to ask about the specific brands of HVAC equipment, the source of the materials they will be using, and the expected lifespan of the structure. Make sure you look closely at the bathroom floor plans and determine whether they include enough storage and accessibility.

The answers to those questions will tell you whether you are looking at a true price comparison or comparing completely different products.