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Understanding iGUIDE Measurements and Drafting Standards

Updated

Overview

Learn how iGUIDE ensures square footage measurement accuracy by following industry-recognized standards such as Alberta’s Residential Measurement Standard (RMS) and ANSI Z765. Understand how these standards support consistent, reliable data reporting and how to navigate measurement discrepancies. 

In This Article

What is Measurement Accuracy in iGUIDE? 

Measurement accuracy in iGUIDE refers to the high level of precision used when calculating square footage and other dimensions of a property. iGUIDE follows the Alberta Residential Measurement Standard (RMS), which is adapted from the ANSI Z765-2013 standard. These are among the most comprehensive and reliable measurement protocols in North America. Looking for more information? Download the Guide to RMS Alberta. 

iGUIDE’s laser-based camera system ensures a low margin of error—about 1% for square footage—and comfortably meets or exceeds the allowed 2% uncertainty specified by both RMS and ANSI standards. All measurements are standardized and legally defensible, making iGUIDE data a trusted source in real estate transactions. 

Download our full Drafting Standard & Policy here. 

Disputes about square footage

It happens from time to time that iGUIDE square footage is compared to square footage from other sources, and questions about which one is more reliable arise. There are a few factors that must be considered here.
 
First of all, as with any comparison, apples must be compared to apples. Square footage is just one number that describes a complex structure such as a house and there is more than one way to arrive at that number, depending on which methodology or measurement standard is used. Different methods mainly differ in which spaces are counted as excluded from the reported square footage. Differences may also come from how sloped ceilings in attics or shared demising walls are treated.
 
The iGUIDE measurement method is summarized here. The iGUIDE method essentially follows the Alberta Residential Measurement Standard (RMS) which currently is the most comprehensive standard in North America. Alberta RMS is based on the ANSI Z765-2013 standard for single-family houses and extends it to condos and apartments in multi-family residential buildings. Alberta RMS was created because square footage in municipal tax records proved unreliable as those values are produced without following any prescribed standard and comparisons between any two properties may or may not be comparing apples to oranges.
 
Secondly, any real measurement has an associated measurement uncertainty or measurement error. The iGUIDE camera allows measuring distances to walls to within 1cm uncertainty. For a typical house, this can mean up to 5cm uncertainty across the whole house when several rooms are stacked or about 0.5% for distance measurements for that typical floor size. The resulting uncertainty in square footage will be about 1% (double the distance uncertainty). Therefore, when comparing iGUIDE square footage to square footage from other sources, any differences smaller than 1% (e.g., 25 sq ft for a 2,500 sq ft house) are meaningless as they are below the measurement noise and thus must be ignored.
 
If the difference exceeds 1%, then the measurement uncertainty of the second number must be examined and the combined uncertainty must be used during comparison. For example, if measurement A has 1% uncertainty and measurement B has 3% uncertainty, then the combined uncertainty is 3.16% (square root of 1% squared plus 3% squared). If the difference between A and B is less than 3.16%, then the two measurements are said to be the same within the measurement uncertainty.
 
If the second measurement uncertainty is not available, then the iGUIDE measurement must be presumed as the most accurate measurement, as no meaningful comparison can be made.
 
Both Alberta RMS (residential measurement standard) and ANSI (commercial space measurement standard) call for a maximum allowed measurement uncertainty of 2% when reporting square footage measurements. As seen from the above, iGUIDE technology meets and exceeds these requirements.
 

Can you look over the iGUIDE again and make sure the numbers are correct?

The Drafting Team goes through a Quality Assurance process and thoroughly checks every iGUIDE before it is uploaded to the Portal to ensure that all floors are drafted correctly. Please provide more specific details as to where you believe any discrepancy may lie to allow us to determine where any confusion exists and provide better explanations.
 
We encourage you to use the on-screen measuring tool in the iGUIDE with which you can measure anywhere on the iGUIDE floor plan. In the PDF floor plans, there are arrows indicating the dimensions of each room and where those measurements start/end. The colours indicate which areas are included in the total square footage with any white space being excluded from the total.
 

Why do iGUIDE numbers differ from tax records?

A tax record's square footage is not considered an accurate total unless the numbers have been independently verified. The measurements are calculated from an estimation of the outside of the structure. The estimator often has not entered the structure and therefore would not be aware of any areas that would be excluded from a total interior square footage area, such as areas open to below, cold rooms, the footprint of the 2nd floor being different from that of the 1st floor, etc.
 

Why do iGUIDE numbers differ from the builder’s floor plan?

Builder’s floor plans describe what the builder was intending to build (build-as). Changes occur during home construction for many reasons and resulting floor plans may differ from builder's blueprints. iGUIDE floor plans describe what was actually built (as-built) and what a real estate agent is selling. It is recommended that after the construction is complete an independent company verifies room dimensions and total square footage as they may differ significantly from the original builder's floor plans.
 
Builders use their floor plans to sell homes that are not yet built and are covered by disclaimers of potential deviations in the sales contract.
 

Requests that go against the iGUIDE Drafting Standard

The Drafting Team drafts every property according to the iGUIDE Drafting Standard. Photographers can leave the Drafting Team a note in the uploaded data indicating a special request. These requests can also be made after the iGUIDE has been completed.
 
If a special request that goes against the iGUIDE Drafting Standard is fulfilled by the Drafting Team, the requester assumes responsibility if the measurements are brought into question. Charges may apply depending on the request.
 

Use Cases

  • Accurate Residential Measurements
    • Real estate professionals in Alberta rely on iGUIDE to comply with RMS, ensuring consistent measurements even in complex properties like condos and multi-family units.
  • Visual Identification of GLA
    • iGUIDE floor plans use color to distinguish finished (included) spaces and white for unfinished or excluded areas, making it easy to determine what counts toward Gross Living Area (GLA).
  • GLA Reporting Based on ANSI Z765
    • The GLA is equivalent to Finished Above Grade area, and can be clearly viewed in imperial PDF floor plans. 

  • Custom RMS Compliance Tools iGUIDE users can: 

    Append Measurement Diagrams to PDFs 

    • In iGUIDE Defaults:
      • Go to your User Settings > iGUIDE Defaults > iGUIDE Viewer > Other Options > Append Measurement Diagrams to PDF (Alberta) > Save.
    • In your iGUIDE:
      • Search My iGUIDEs > Click the blue Edit button > Options > Append Measurement Diagrams to PDF (Alberta) > Save.

    Add Custom Text to PDF reports (e.g., surveyor confirmation, area instructions)

    • In iGUIDE Defaults:
      • Go to your User Settings > iGUIDE Defaults > iGUIDE Viewer > Default PDF Custom Text > Save.
    • In your iGUIDE:
      • Search My iGUIDEs > Click the blue Edit button > Custom Text for PDF > Save.

    Insert Additional Notes to clarify total areas and measurement responsibilities 

    • In iGUIDE Defaults:
      • Go to your User Settings > iGUIDE Defaults > iGUIDE Report > Default Report Notes > Save.
    • In your iGUIDE:
      • Search My iGUIDEs > Click the iGUIDE Report button > Additional Notes > Send.

Important Notes

  • Uncertainty Exists Across All Measurements
    • Any differences in square footage below 1% are considered insignificant. Larger discrepancies require knowledge of the comparison method’s margin of error.
  • Varying Standards Lead to Misleading Comparisons
    • Municipal tax records or alternative measurements may not follow a consistent or recognized standard, leading to confusion. iGUIDE’s adherence to ANSI/RMS ensures consistency.
  • Room Height Rules Apply
    • Finished rooms must have a minimum floor-to-ceiling height of 7ft (2.1m). Rooms with sloped ceilings are only included if the ceiling height exceeds 7ft in at least one spot and are measured from 5ft (1.5m).
  • Wall Thickness Handling
    • Perimeter wall thickness is measured once—usually at the main entrance—and not adjusted for variations around the property. See how to measure the exterior wall thickness here.
  • The sum of the areas of all listed rooms will not add up to the total square footage.
    • The iGUIDE property details section displays dimensions and floor areas for major rooms only, measured paint-to-paint, while excluding areas like closets, hallways, and interior wall footprints. Total floor area includes all floor plans except non-habitable or excluded spaces (e.g. garages, balconies). Due to rounding, the displayed total may differ slightly—typically by about 1 sq ft—from the sum of individually listed room areas.
  • Multiplying room width and length will not result in room floor area unless the room has the simplest rectangular shape.
    • Multiplying a room’s width by its length will only provide an accurate floor area if the room is a perfect rectangle. Most rooms have more complex shapes, such as alcoves, angles, or irregular walls, so iGUIDEs are calculated using precise measurements rather than basic length × width formulas.

Frequently Asked Questions

Q: Why is my square footage different from another source?
A: Differences often stem from the use of different measurement standards or unknown uncertainty margins. iGUIDE’s 1% margin of error is exceptionally low and should be the benchmark for reliability.

Q: Why are some rooms shown in white on the floor plan?
A: White indicates excluded or non-reported areas. This could be due to unfinished space, insufficient ceiling height, or space being open to below.

Q: Why weren’t room dimensions included for all rooms?
A: Only major rooms have dimensions shown. Minor rooms (e.g., foyers, closets) are hidden to maintain clarity, but this data is available on the Portal.

Q: Can iGUIDE accommodate varying wall thicknesses?
A: Wall thickness is measured once and applied uniformly. It does not adjust dynamically for variations.

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