Gross Lettable Area (GLA)

Let’s be honest... most landlords, tenants and even some agents think they understand Gross Lettable Area (GLA).

But when you ask how it’s actually measured, what’s included and how it impacts their rent or valuation… you’ll get a dozen different answers.

Here’s the truth:

One simple mismeasurement in GLA can cost or save you tens of thousands.

That’s why, as someone who manages, negotiates and audits commercial properties every single day, I’m going to break down exactly what Gross Lettable Area (GLA) means and how to make sure it’s working in your favour.


What Is Gross Lettable Area (GLA)?

Gross Lettable Area (GLA) is the total floor area of a commercial or industrial property that can be legally leased to a tenant, measured from the outside surfaces of the external walls or the centreline of shared walls between tenancies.

In simpler terms?

It’s everything within the walls of the building that a tenant can reasonably use or occupy plus the areas that directly support that space.

Think:

  • Warehouses
  • Industrial facilities
  • Showrooms
  • Big-box retail sites

If NLA (Net Lettable Area) is about usable space inside an office…

GLA is about total operational space for large-scale commercial properties.

What’s Included in GLA?

When calculating Gross Lettable Area, we include every area that forms part of the usable structure, such as:

  • Toilets and washrooms
  • Internal stairs and landings
  • Plan and equipment rooms
  • Lift shafts
  • Loading docks (if covered)
  • Storage areas
  • Cupboards and service spaces
  • Structural columns, piers and internal walls

Basically, if it’s built in and forms part of the physical footprint, it’s counted.

What’s Not Included?

However, GLA excludes areas that aren’t actually part of a tenant’s direct use or lease entitlement:

  • External open areas or yards (unless enclosed)
  • Common corridors in multi-tenant buildings
  • Shared foyers or public lobbies
  • Public thoroughfares or public car parks
  • External awnings or balconies

In a single-tenant building, nearly everything is included in the GLA because the tenant controls the entire space.

But in multi-tenanted buildings, shared areas are excluded because they don’t belong to any one tenant.

 

How Is Gross Lettable Area Calculated?

GLA is defined and calculated under the Property Council of Australia’s (PCA) Method of Measurement which is the national industry standard.

According to the PCA, GLA is measured:

From the outside face of the external walls or the centreline of shared walls, including all enclosed structures such as plant rooms, stairwells, service areas, and covered loading docks.

For single-tenant buildings:

  • All enclosed spaces within the external walls are included.

For multi-tenant buildings:

  • Includes those parts exclusive to a tenancy are counted in its GLA.

Example: Measuring a Warehouse

Imagine a modern warehouse that’s 1,200m² in total, measured externally.

It includes:

  • 950m² of warehouse floor space
  • 150m² of office
  • 50m² of amenities (toilets, kitchenette, plant)
  • 50m² of covered loading dock

Total GLA = 1,200m²

The entire built footprint under the roof is rentable, because it’s enclosed and functional.

Now, if that same building had two tenants, with separate amenities and shared accessways - those shared spaces would be excluded from each tenant’s GLA and instead allocated proportionally or managed as common area.

 

GLA vs NLA - What’s the Difference?

This is one of the biggest sources of confusion in commercial leasing.

Feature

Gross Lettable Area (GLA)

Net Lettable Area (NLA)

Used For

Industrial, warehouse, showrooms, retail

Office buildings, commercial suites

Measured From

External wall surfaces

Internal finished walls

Includes

Toilets, plant rooms, stairs, loading bays

Usable office space only

Excludes

Public corridors, external spaces

Lobbies, lifts, toilets, tea rooms

Best For

Single-tenant or large industrial

Multi-tenant office spaces


Think of It Like This:

  • NLA = Usable workspace
  • GLA = Everything under the roof

If you’re leasing an office suite then NLA is your metric.

If you’re leasing a warehouse then GLA is the king.

You can read more about the comparisons between Net Lettable Area and Gross Lettable Area here.

Why GLA Matters (and How It Impacts Your Bottom Line)

You might be thinking,

“Okay, it’s a measurement standard... so what?”

Here’s why it matters:

GLA determines how much rent you can charge or pay and how your property is valued.

That means getting it wrong can destroy your returns or blow out your expenses.


For Landlords

GLA drives your income potential.

If you overstate your GLA:

  • Tenants can challenge the lease
  • You risk rent disputes or refunds
  • Your property looks overpriced compared to market rates

If you understate it:

  • You leave money on the table - permanently

Every single square metre counts.

When you multiply your rent rate (say $450/m²) by an incorrect GLA, even a small error compounds across the term of the lease.

For Tenants

For tenants, knowing your GLA ensures you’re not paying for space you can’t use.

Questions to ask:

  • Was the area measured externally or internally?
  • Does it include loading docks or stairwells?
  • Are shared amenities or service areas fairly allocated?

In retail and industrial leases, this clarity can save you thousands annually in rent and outgoings.

For Valuations and Finance

Lenders and valuers use GLA as a core input in property appraisals.

If your building’s GLA isn’t validated against PCA standards, it can distort your asset’s value and refinancing potential.

 

The PCA Method - Australia’s Gold Standard

The Property Council of Australia’s (PCA) Method of Measurement for Lettable Area was designed to eliminate inconsistency between owners, tenants and valuers.

Here’s what it enforces:

Standardisation: Every property uses the same benchmark

Transparency: Both parties know what’s included/excluded

Fairness: No “creative measurements” to inflate rent

Auditability: Independent surveyors can verify accuracy

When negotiating leases, make sure your agreement explicitly references the PCA Method of Measurement not just “GLA by plan” or “approx. GLA.”

That one clause could save you from expensive disputes later.

 

Case Scenario Example - A $45,000 GLA Oversight

A client purchases an industrial site in Brisbane.

The previous owner’s lease stated 1,000m² GLA.

Our audit found the actual built area was 1,074m².

The old agent had rounded down “to keep the rent simple.”

That “simplification” meant the landlord had missed:

74m² × $600/m² = $44,400 in annual rent

Over a 5-year term? That’s $222,000 lost.

All from a measurement error that would have taken one professional surveyor an afternoon to verify.

That’s the cost of not understanding your Gross Lettable Area.

 

When to Use GLA

GLA is the standard for:

  • Warehouses and distribution centres
  • Industrial complexes
  • Showrooms and bulky goods retail
  • Standalone retail (e.g. supermarkets, car dealerships)
  • Large format retail centres

It’s perfect for single-tenant buildings, where internal amenities form part of the leaseable footprint.

For office towers and multi-tenant buildings, NLA is used instead.

 

GLA in Valuation and Yield Calculations

When valuers calculate a property’s worth, GLA directly affects:

  • Rental yield
  • Cap rate
  • Gross realisable value

Example:

$500/m² × 3,000m² GLA = $1.5M annual rent

At a 6% yield, that property’s worth ≈ $25M

If that 3,000m² was mismeasured and should actually be 2,950m², you’ve just wiped $830,000 off the valuation.

That’s why I tell my clients:

“You don’t just manage what you measure - you profit from what’s measured correctly.”

 

Common GLA Mistakes That Cost Owners Big

Using architectural drawings, not as-built measurements

- Plans change. Only measure the final structure.

Ignoring PCA definitions

- Not all “floor space” is lettable. Follow the standard.

Failing to remeasure after renovations or extensions

- Every wall shift can change your GLA - and therefore, your rent potential.

Not differentiating between GLA and NLA

- Different property types demand different standards.

No documentation or survey verification

  • If it’s not documented, it’s disputable.

 

How GLA Affects Outgoings and Rent Reviews

Your GLA also determines your share of outgoings, maintenance costs, and insurance allocations.

For example:

  • Body corporate fees and insurance are usually calculated by area.
  • Rent reviews (CPI or market) apply to the rent based on GLA.

That means an inaccurate measurement can ripple through every financial aspect of your lease, not just the base rent.

 

GLA and Lease Negotiations

When negotiating a lease:

Confirm the measurement source.

Ask: “Is this GLA PCA-compliant and independently verified?”

Document it in the lease.

The lease should specify the exact GLA (to one decimal place) and the measurement method.

Adjust for tenant modifications.

If a tenant installs or removes structures that change the enclosed area, update your GLA accordingly.

Review after fit-outs or subdivisions.

New walls or mezzanines may alter usable space and GLA should reflect that.

 

The Relationship Between GLA, Rent and Market Position

The market rent rate ($/m²) means nothing unless your GLA is right.

A property advertised at $400/m² for 1,000m² equals $400,000/year.

But if your actual lettable space is 950m², your real rent is $421/m² - suddenly you’re overpriced compared to competitors.

That can make the difference between a signed lease and a 6-month vacancy.

 

GLA, GFA and NLA - Understanding the Hierarchy

In case you’ve seen these terms thrown around interchangeably:

Term

Meaning

Used For

GFA – Gross Floor Area

Total built-up area including walls

Town planning & construction

GLA – Gross Lettable Area

Enclosed lettable area

Industrial & retail leases

NLA – Net Lettable Area

Usable tenant space

Offices & commercial

They’re related but not the same.

GFA is for design, GLA is for leasing, NLA is for occupancy.

 

The Smart Investor’s Approach

Successful landlords don’t just accept the numbers handed to them.

They verify, document and leverage them.

Here’s the playbook:

  1. Commission a PCA-compliant surveyor to measure your GLA.
  2. Store that certificate with your lease documentation.
  3. Use verified GLA figures in all rent, valuation and insurance calculations.
  4. Reassess after every major building alteration.

Because the smartest investors don’t just own assets, they understand them.


At the end of the day, Gross Lettable Area (GLA) isn’t just a technical definition.

It’s the backbone of every rent, lease and valuation decision you’ll ever make on a commercial property.

When measured right, it protects you.

When measured wrong, it bleeds you dry quietly over years.

If you’re buying, leasing, or managing an industrial or retail property - get your GLA verified, documented and aligned with the PCA standard.

Because what you don’t measure correctly, you can’t profit from confidently.

Back to blog