Using PlanSnapper · 5 min read

How to Measure a Manufactured Home for GLA

Manufactured homes follow the same ANSI Z765 exterior measurement rules as site-built homes — but there are important nuances around the hitch, additions, and how to handle HUD-code construction. Here is what appraisers need to know.

Exterior measurement still applies

Under ANSI Z765-2021, all residential GLA is measured from the exterior of the structure. Manufactured homes are no exception. You measure the outside dimensions of the main body of the home and calculate the gross area from those.

What you do not include: the tongue, the hitch mechanism, any tow bar extensions, or exterior utility compartments. These are structural components for transport, not living area. If a skirt or siding wraps around these elements, measure to the start of the actual habitable walls.

Single-wide vs double-wide vs triple-wide

For a single-wide unit, the measurement is straightforward: length times width of the main body. Most single-wides are rectangular, which makes this simple.

For double-wide and triple-wide homes, the sections are joined on-site. Measure the overall exterior footprint of the combined structure, not each section separately. The marriage wall between sections is internal and does not affect the exterior measurement.

Additions and room expansions

Many manufactured homes have additions — enclosed porches, bump-outs, extra rooms built on a concrete slab or permanent foundation. These are a common source of GLA disputes.

An addition counts as GLA only if it meets all the standard requirements: above grade, finished, directly accessible from the main living area, and heated and cooled to a similar standard as the rest of the home. An enclosed porch with no heat source does not qualify, even if it has walls and a roof.

Appraisers should also note whether the addition was permitted and built to the same quality standard as the original HUD unit. Lenders — especially for FHA and VA loans — may require additional documentation when the addition quality is inconsistent with the main structure.

HUD-code vs modular: a critical distinction

A manufactured home (HUD-code) is built to federal HUD standards and transported to the site. A modular home is built in sections in a factory but must meet local building codes — it is treated as real property and appraised the same as any site-built home.

GLA measurement rules are the same for both. But the appraisal form, lender guidelines, and market comparability issues are very different. Make sure you are correctly identifying the construction type before you start measuring.

Using PlanSnapper with a manufactured home floor plan

If you have a floor plan for the manufactured home — from the manufacturer's data plate, county records, or a prior appraisal — you can upload it to PlanSnapper and trace the exterior footprint to get the GLA calculation.

Set your scale using a known wall dimension (the data plate often lists the exterior dimensions of the unit). Trace the main body, then trace any qualifying additions separately. PlanSnapper will calculate each polygon's area, and you can sum the qualifying sections for total GLA.

For non-rectangular single-wides with bump-outs, use the polygon tool to trace the actual exterior outline rather than estimating with a rectangle.

What about the data plate square footage?

Manufactured homes come with a HUD data plate that includes the manufacturer's stated square footage. This number is often close to the ANSI GLA calculation, but it may differ — manufacturers sometimes measure to interior wall surfaces or use slightly different methods.

For appraisal purposes, always measure the exterior yourself and calculate GLA per ANSI Z765. Do not rely on the data plate number as your reported GLA. Note the data plate figure in your comments for reference.