Does it Matter?
As detailed on our 2025 Research post, both buyers and sellers highly value floor plans. But what about floor plan accuracy. Does it matter? Do people care?
Based on the popularity of some of the “apps” out there, and the lack of accuracy of those floor plans created from those apps, I am not sure. Or do people not know the truth, or the implications of using inaccurate data….?
From my perspective, it should matter. Buying a house is one of the largest transactions most people ever make, and don’t you as the buyer want to know what you are getting, with a high degree of certainty? As the seller, or the marketing agent for the seller, you also do not want to misrepresent the product you are selling. The size impacts the value, and it can also impact the cost of ownership over time.
Why Accuracy should matter!
Let me tell you a story of my own personal homeownership experience and why it DOES matter.
When my family moved to the burbs of Seattle in 2005, we bought a pretty big house – it was listed at 5290 square feet on the listing and in the King County tax record. Yes we bought more than we really needed, but it was on the same street as our good friends so it seemed right. Well, in 2024, we sold that house when we moved to Dallas, and when we listed it, we listed it at 4840 square feet.
Wait. What? Where did 450 square feet go. How did we virtually downsize over 19 years in the same house?
We didn’t. It turns out, the house we thought was 5290 square feet was not that big. The King County Tax Assessor had errored in drawing the foot print and recording of the property, and the listing agent in 2005 just took what the county said, and there you go.
Based on what I paid for the house, I overpaid by $98,500. Based on what I sold it at, I could have overstated the value by $265,000! However, given the fact I have scanned my house 50+ times with various methods, and I had a true source floor plan generated from a Matterport scan with a Pro2 camera and calibrated with hand laser measurements, I went to King County and got them to change the square footage from what they had it listed at…except now they understated it because when they redrew, they left off some areas like stairs, which should be accounted for on both levels. So, we ended up using the HomeDiary Certified Square Footage Report square footage of 4840 square feet as the listing size. See the report here. I am pretty sure this floor plan is 100% accurate as the individual room measurements match my hand laser measured numbers on a room by room basis.
As you can see in the below screenshot, I overlaid the original King County floor plan foot print with the second floor Matterport scan as a layer. It is clear by this overlapping view, the whole upstairs was overstated with an area that did not exist when you see the Matterport layout scaled exactly with the footprint – the red box area was counted by the county as upstairs living space, but it is basically the roof over the downstairs office. Initially, I thought the county had just counted the 2 story open to below foyer as living space as it was a similar square foot area, and I did not have it changed because if they did that consistently for all houses, it would put my house at a disadvantage. It wasn’t until I saw one of our clients with a listing that had the exact same floor plan as my house with smaller total square footage that I took a closer look into why my house was off. Then I discovered the error. Had I fixed it a long time ago, I would have saved over $20,000 in property tax. Washington state does not have income tax (yet), but they get you on sales and property taxes!
So, the correct square footage could have saved me some on the purchase initially perhaps, it could have saved me a lot over the 19 years of ownership in the form of less property taxes, insurance, home warranty (it was more because the house was listed as over 5000 sq ft), etc, etc.., and a floor plan that can be edited, shared, and used in home improvement and visualization has been instrumental in my homeownership journey once we added this feature into the HomeDiary platform. We can do the same for your listings and your clients’ and customers’ homes.
Over the years we also had 3 appraisals, and I had Home Depot, Allstate, Costco, and others come out and they all created floor plans. Why is there no reusable, true source for a floor plan? Humm…sounds like a HomeDiary feature opportunity.
You can see below, just because a “Home Pro” is doing the measurement does not mean they can or are creating accurate floor plans. The last appraisal of our home had a floor plan that looked nothing like our house, and it was 7% off from actual (middle top row is that appraiser’s floor plan). Every appraisal I have had was different, with the purchase appraisal coming in at around 5000 sq ft, another one at 4798, and this final one being 5161.
Do Consumers Value Accuracy?
According to the WAV Group study in 2025, buyers do want accurate floor plans as well, and the accuracy not only applies to the overall square footage, but to room dimensions.
- 98% of buyers want to know the measurement standard
- 99% of buyers want to know the total square footage of the home
- 100% of buyers think it is valuable to have measurements and overall size of the lot
- 92% of buyers want to use the floor plan to do furniture placement and other planning activities, which require accurate dimensions, square footage and at a minimum, an interactive 2D floor plan with a furniture library.
HomeDiary Creates Accurate Floor Plans with Interactivity
HomeDiary uses Matterport in most markets, and recently switched to iGuide in North Carolina. It also has appraisers on staff that are also photographers. Matterport with a 360 camera is typically 98-99% accurate based on our tests. Matterport with a Matterport Pro camera is at least 99.5% accurate. iGuide with their 360+lidar system is also at least 99.5% accurate, which is why in North Carolina we are going with this tech solution – it is also a lot faster to use than Matterport’s Pro2 camera, and even Matterport with a 360 camera.
Regardless of the source, we convert the data into the HomeDiary floor plan format, so the plans are 2D and 3D interactive tools that are real-time editable, shareable and transferrable to the buyer (and optionally the seller as a keepsake). Generally, these scan methods are more accurate than traditional hand measurement methods, and they are more accurate than other app solutions (see below). Because the whole house can be seen in one layout, it is more accurate for our production team to reconstruct the “as built” floor plan using this data than other methods.
We provide the basic living and non living data as part of creating the floor plan, and if you want a more official GLA report with more details that can be added to the tour, like this GLA Property Report, there is a small upcharge fee. We draw plans according to the ANSI Z765-2021 Standard. Either way, we leverage the data to create accurate floor plans people can use and rely upon. And use post sale as part of their free HomeDiary experience, that is integrated into our virtual tours as well.
Appraiser Results
For my Texas house, I have had 2 appraisals. The tax record, as stated, shows a total of 4197 square feet of living space. The purchase appraisal came in at 4198 sq ft, but in looking at the report, I can see inaccuracies on how the floor plan was drawn, and since the appraiser used Cubicasa, those inaccuracies coupled with the exterior walls being at 6 inches vs the actual 10 inches (since our house is 100% brick on the exterior) offset each other.
The second appraiser used traditional, hand measurement methods and came up with 4201. I corroborated his exterior measurement results with my own measurements using a 100 ft tape. Results of both are below and measurements where the appraiser errored are in the orange boxes. This appraiser came up with a number close to the tax square footage, but again, there were some errors in his numbers, including some of the exterior numbers being off from actual, and counting an area in the garage as part of the living area, yet it is not heated space because it is actually part of the garage, not the mud room inside. So these errors just happened to get the end result close to the tax record – understated some areas, overstated others.
Below you can see the appraisers floor plan footprint overlaid with the Matterport OBJ file as a 2D layer. There are several areas that are incorrect, including the area in the garage that was counted as part of the mud room living space, the garage being larger than it is per Matterport, no curved walls with the primary bedroom and then some dimensions were off as noted. For example, you can see in the area marked as Bonus, where the appraiser had it as 34’11” but I measured it at 34’7″ and you can see it is actually shorter per the Matterport scan than 34’11” so I am pretty sure my numbers, and Matterport, are the right numbers.
Again, just because a “home pro” is doing the measurement does not mean it is right, or always right. With technology that maps the actual space with laser accuracy, we can get there.
These screenshots show the errors in the appraisers floor plan foot print. Click to see a larger view.
Matterport Pro Cameras.
As you can see from the Matterport Pro2 camera scan layout below, there’s lots of detail to get pretty accurate when drawing the floor plan. In the Matterport or in the HomeDiary floor plan engine, you can even tell the external wall thickness is 10 inches thick since the covered patio was also scanned so the walls between the living room, primary bedroom and dining room all show that thickness. Plus the walls are straight, rooms are at the right angles and put together in the right spots. There is no drift that you get with the apps, even with Matterport and 360 cameras. So, it is one of the more accurate ways to create a floor plan, and with the HomeDiary team tweaking it to get more precision on the wall thickness, etc, it can get even more accurate. Note if Matterport is creating the floor plan, they use a standard 6 inch thick wall and it can’t be changed on a property by property basis. We can and do change wall thickness when we create the floor plan from Matterport, or any other source.
iGuide Accuracy.
The iGuide camera system leverages a custom lidar and 360 camera unit. Each camera is around $2,700 and then there is a cost for each floor plan processed. Because it uses lidar, the room dimensions and overall square footage is highly accurate, to within ±10 millimeters. As you see in the floor plan comparison, individual room dimensions are either right on with a hand taken laser measurement or 1 inch off at most. Even doing a laser measurement can get you a slightly different result each time, so this is deemed acceptable. You can see the various methods below of the Demo House scans, and accuracy compared to the presumed true source. Methods used include: Matterport, iGuide, Cubicasa, Zillow, WeScan, and 2 appraisals.
In Canada, iGuide is pretty much the standard because one province, Alberta, requires listings to have an accurate floor plan when it is listed for sale. The Residential Measurement Standard (RMS) requires floor plans to be created pretty much to the same standard as the ANSI standard for drawing floor plans, and they are required to be at least 98% accurate. You can read about their standard here.
Below you can see a screenshot of the iGuide app after a scan of our demo house. This is the point cloud data captured by the lidar system and you can see how detailed it is in capturing information. It is a bit different than Matterport, which shows more of the actual space visual, but detailed nonetheless.
If you zoom in on the app, you can see the scan creates very detailed captures of spaces, like these curved walls and the thickness of the walls, which can also be corroborated, especially if some of the outside is captured as well, such as a front porch or back patio. The areas where you see information bleeding outside of the walls are windows. Just click these images below to see a larger, more detailed view.
Accuracy Comparison – iGuide v Matterport
In the video below I show you how accurate iGuide is vis-a-vis the Matterport OBJ 2D layout. You can see things match up fairly well, so it is a validation of both systems really, and both systems were within a few square feet of each other. Remember – my Seattle house had 3 appraisals, and there was a variance of 363 square feet between the 3, and if I threw in Home Depot, it is over 600 square feet of variance between 4 “home pros” measuing and creating a floor plan. You do not get this wide of variance with these proven technology solutions.
How accurate are other apps?
OK, now let’s look at a couple of the more popular apps out there, Zillow and Cubicasa. The accuracy of these popular apps may surprise you. As I said, I have scanned my 2 homes, along with numerous clients, friends and neighbor homes over the years, many times, so I consider myself kind of an expert when it comes to using apps and technology solutions for creating floor plans. For this analysis I am looking at my new home in Texas and comparing my results done with Matterport using both a Pro2 and Pro3 camera, as well as a Ricoh Theta Z1, an iGuide Radix camera system, and the Zillow 3D Home app, Cubicasa and a few other apps.
The most accurate – Matterport with a Pro2 camera and iGuide. ~100% accurate puts the GLA of my home at 4240 sq ft. iGuide came in at 4242 sq ft, so almost the same. The county tax record has it at 4197. So, I actually got a little more house for the money! Yippie!
The most inaccurate was Zillow. Depending on what wall thickness I use, Zillow was off 10% to 13.7% (if I used the actual 10″ wall thickness, it was 10% off, if I used what Zillow used on their floor plan provided of 4.5″ walls, it was off almost 14%. The thinner the external wall, the more inaccurate it was…). This result is well beyond the realm of acceptability. No wonder their terms of use state you can’t do anything with the floor plans and they are not to be used for design or remodeling purposes. They are too inaccurate to do anything with from a home improvement perspective other than just look at the general layout.
Cubicasa was better, but each time I got a different answer even though I was using the same device, and with lidar, it was still 3.7% to 4.3% off and individual room measurements can be off over 1 foot. So it was consistently inconsistent.
Continue with the analysis below where I overlay both Zillow and Cubicasa floor plans with the Matterport layout as a layer to see where it is off as well, so even through Cubicasa was closer, certain parts of the house where way off from reality, as you see below.
Zillow Floor Plan Analysis. In this screenshot below, you can see the GLA, or total gross living area calculated using the Zillow floor plan and 6″ thick walls, which is the appraisal standard. The Zillow floor plans are drawn with 4.5 inch walls, so I used the appraisal standard instead. I also drew it with external walls at 10″ thick, as the HomeDiary floor plan system supports varying wall thicknesses, and my Dallas house is 100% brick on the outside, and it is 10″ thick. A typical 2×6 wood framed house is going to be 6 5/8 inches thick….which is why we normally use 6.5″ but to get closer to what Zillow likely used, I used 6″ in this case. At the 4.5″ thick walls Zillow used to draw the floor plan, it is off 13.7%!
As you see, the thicker the outside wall, the more square footage in the total, because apps like Zillow and Cubicasa use the interior wall face to create the floor plan, not the exterior, and they typically do not know wall thicknesses. Often times with Matterport, you can see the wall thickness as you are creating the floor plan (see below for my house). Or, since we have someone onsite, we can confirm visually how thick the walls should be drawn.
The Zillow layout is also off. The Matterport layer was scaled and aligned with the entertainment room on the upper right of the floor plan. You can see the whole left side of the house is off fairly significantly from a footprint perspective. I traced over the Zillow plan exactly as they created it, and the red dashed lines and green area are the outside of the outer wall face, and the green area is all interior GLA of the living spaces.
At 12.5% off, that is $148,200 in value based on what I paid for my house. Seem like a significant difference.
Cubicasa Floor Plan. In this screenshot below, you can see the green GLA calculated using the Cubicasa floor plan at 6″ thick walls, which is the only thickness Cubicasa supports. In this case, the GLA came out to be 4064 sq ft, or over 4.2% off, and this was done using an iPhone 14 Pro Max with Lidar, the most accurate way to scan with Cubicasa. Since this was a Lite scan, the total area provided by Cubicasa was 4058, so slightly off what I calculated in the HomeDiary system, or 4.3% off from reality. You can see the layout of the floor plan vis-a-vis the Matterport layout is off on the left side of the house, as well as at the front (bottom here) and then into the garage. The 4% off is about $50,000 in value based on what I paid for my Texas house. Seems like a significant number to me.
In this video I compare the Cubicasa floor plan (the most accurate one it could create) to Matterport via the OBJ file created, which is one of the most accurate 3D objects available for real spaces.
Matterport + 360 Camera. Below you can see a floor plan created from a Matterport made with a Theta Z1 360 camera scan (note the orientation is flipped 180 degrees from the other plans above). It is a little over 99% accurate, or .97% off as it came in with GLA of 4282 sq ft. So slightly larger than actual. You can see the area over by the garage got a little elongated, as did the entertainment room by about 6 inches. Other areas were pretty close with the Matterport Pro2 scan, which I put in as a background layer for reference. Note, while I have not scanned my house with an iPhone and the Matterport rotator yet (I will at some point), in my old house it came in at about 99.4% accurate, as you see above with the various results on my old house. It just takes more time as it has to rotate 360 degrees for each spot, so you are looking at something like 2:40 minutes per spot vs about :20 for a 360 camera/Pro3 scan or :40 for a Pro2 scan.
In summary. The apps are good to get a visual of the layout. They are not good if you want to rely on the floor plan for anything other than looking at the layout. Plus, they come in jpeg or PDF formats – they are not interactive, unlike the HomeDiary 3D floor plan models we create for every property that are real-time editable, shareable and transferrable to the new owner.
Ultimately, I would pose this question: why go to the trouble to get a floor plan only to say you can’t rely on it for anything, you need to do your own independent verification (redo the work), and you can use it for anything, other than to stare at it?
Sure, having the layout is great and people want to see it but I think they also want to use it as a tool to get estimates for new carpet, paint, a room remodel, place furniture, landscape planning, or who knows what. According to our research, 2//3rds of homeowners want an HGTV-like 3D floor plan tool for their own home. The better the floor plan is, the more utility it has in the future for any purpose. And if you, the marketing agent, are the one providing the more accurate floor plan, every time the homeowner comes back to use the floor plan (which I could have at least 19 times over 19 years of ownership for various projects), they will see you as the provider of that floor plan for their home.
The HomeDiary floor plans can meet the standard and needs of homeowners, and if you want to know with a high level of accuracy how big a house is, we have our Certified Square Footage addon in certain markets to tell you, so you and others can rely on the numbers. Given potential lawsuits that could happen…or in my purchase case, really should have happened, it may pay for itself many times over to get accurate numbers upfront vs pay later. Even if you get sued and win in court, you have legal fees to pay, and believe me, that is not a fun, or profitable way to spend your hard earned dollar.
Now, these are my results for my house. You may get different, more accurate or less accurate results. How will you know unless you have a 100% or close to it true source? When the Cubicasa app first came out, I went to a photography conference and I asked a photographer that was using it if it was accurate (it was early on and I knew it was not). He said: “I don’t know…. I guess it is since people are using it”. Right.
Do you want to trust your business with that kind of answer? We still don’t know, because each time you will get a different answer. And it is not to say with our Certified Square Footage addon we would not get a slightly different answer either, but it is not going to be percentages off…it would be decimals of a percent off, as humans are working on these plans and there is always a potential for human error. And the output is only as good as the input and often people go so fast that spaces or areas get missed and that impacts accuracy too.
It is clear by the above analysis: not all floor plans are created equal, and the HomeDiary plans are more accurate, they are real-time editable by both real estate agents (or home pros) that order them, and then when the homeowner claims the home, the version copied over into that person’s HomeDiary account is also real-time editable, and now its their version they can do anything they want with it. Pretty cool. You can even use it to plan a new pool, like I have done with my Texas house. This one true-source floor plan can be a tool used by the homeowner, and connected home pros, throughout the lifecycle of ownership. It’s only available with HomeDiary, and its integrated into your virtual tours, right now.
