Campervan Materials Calculator

Q: What thickness of plywood should I choose for the floor?

The floor will support the entire weight of your conversion (furniture, tanks and people). You should use robust plywood at least 15mm thick (ideally birch or okoumé). Avoid OSB or MDF, as they are too heavy and can swell when exposed to moisture.

Q: What thickness of timber should I use for the walls and ceiling?

For the walls and ceiling, the aim is to keep the overall vehicle weight down. Thin 5mm or 8mm plywood, or very thin tongue-and-groove panelling, is generally used. As the timber is screwed into the battens (or the vehicle body), it will naturally follow the van's curves without excessive force.

Q: How many square metres does a roll of Armaflex contain?

It depends on the thickness you buy (the carton is always roughly the same physical size). A carton of 19mm Armaflex AF contains a 6m² roll. A 13mm carton contains 8m². A 6mm carton (for thermal bridges) contains 15m².

Q: Should I deduct my windows from the area to be insulated?

Yes, absolutely! If you have large windows in the rear and side doors, plus roof vents, they can easily account for 2 or 3m² of surface area. Failing to deduct them from the calculation could mean buying half a roll of Armaflex that you don't need.

Q: What is the 6mm Armaflex recommended by the calculator used for?

The 6mm (or 9mm) is used to break thermal bridges. The van's structural ribs protrude into the living space. You can't fit 19mm insulation over them without losing too much space, and it wouldn't bend properly. Instead, use a very thin and flexible roll to cover these metal ribs.

Q: How do I calculate the amount of timber battens I need?

Battens are used to create the framework that your wall and ceiling lining will be screwed to. As a general rule, allow around 1.5 to 2 linear metres of battens for every square metre of wall and ceiling area. Always allow a generous amount of spare material, using lightweight structural timber such as softwood.

Q: Do I need to insulate the floor to the same thickness as the ceiling?

Not necessarily. Heat rises, so the ceiling is a critical area for heat loss in winter and overheating in summer. The floor is less exposed. Many converters use two layers of 19mm insulation on the ceiling, but opt for expanded cork or extruded polystyrene (XPS) boards under the floor to avoid losing too much standing height.

Q: Can I return any leftover materials?

For timber (if it has been cut to size or is slightly scratched), this is generally not possible. For Armaflex, if the packaging is intact and unopened, most specialist retailers will accept returns within 14 days, but return postage costs (especially for bulky items) will often be your responsibility. It's better to calculate carefully in the first place!

Armaflex Insulation & Timber

Stop guessing material quantities! Calculate the exact internal surface area (m²) of your van (SWB, L2H2, Trafic...)
and generate an accurate shopping list for Armaflex insulation, sound deadening, and ply lining.

📏 Interior Dimensions

Important: Enter the internal dimensions (usable space) of the cargo area to be converted, not the vehicle's external dimensions.

Van Preset (Average Internal Dimensions)

Length

Width

Height

🪟 Non-Insulated Areas (Windows & Vents)

Enter the combined surface area of windows and roof vents to deduct them from the calculation and avoid over-ordering materials.

Total Glazed & Opening Area e.g. 2 side windows + 1 roof fan ≈ 1.5 m²

m²

📦 Material Standard Sizes

Insulation Roll Size (Standard 19mm Armaflex: 6m²)

m²

Ply Sheet Size (Standard 8ft x 4ft sheet ≈ 3m²)

m²

Total Net Surface Area 0 m²

🔥

Thermal Insulation (Armaflex)

19mm Armaflex (Main Area)
Ceiling, walls, and floor

0 rolls

6mm or 9mm Armaflex
Structural ribs (thermal bridges)

0 rolls

🪵

Timber & Plywood Lining

12mm / 15mm Plywood
Subfloor lining

0 sheets

5.5mm / 9mm Lightweight Ply
Walls and ceiling lining

0 sheets

Why Calculate the Materials You Need for Your Campervan Conversion?

Starting a campervan conversion often means making some big purchases. This is the stage where your budget can take the biggest hit: you need to order thermal insulation (Armaflex, spray cork, sheep's wool) and timber sheets (plywood, tongue-and-groove panelling) to create the shell of your future home on wheels.

The problem is that these materials are expensive and bulky. Ordering one extra roll of 19mm Armaflex can mean around £100 wasted. On the other hand, if you're missing just one sheet of timber to finish your ceiling on a Sunday afternoon, your entire project can come to a standstill. Our campervan surface area and materials calculator gives you an accurate shopping list, including a safety margin for waste!

How Do You Calculate the Surface Area (in m²) of a Campervan?

Our tool automates a time-consuming calculation. It doesn't use the external dimensions (the measurements provided by vehicle manufacturers), but the usable internal dimensions of the cargo area.

It adds together:

The floor and ceiling (Length × Width)
The side walls and doors (Perimeter × Height)

It then deducts your glazed areas (windows, roof vents), because you obviously won't be covering these with insulation. Finally, it applies a vital safety margin (10% for flexible insulation and 15% for rigid timber) to account for complex cuts around wheel arches and structural ribs.

The Armaflex Trick: Don't Forget Thermal Bridges!

Armaflex (a flexible elastomeric rubber insulation) is the gold standard choice for campervans. For the floor, ceiling, and large flat wall sections, 19mm insulation is generally used (or double layers in colder climates).

However, many beginners forget about the metal ribs (the structural reinforcements in the vehicle body). If you leave them exposed, the metal will conduct cold directly into the living space, creating a thermal bridge and severe condensation point. Our calculator automatically allows for a roll of thin Armaflex (6mm or 9mm), which is flexible and specifically designed to cover these metal ribs without taking up valuable interior head height.

🛠️ Build on a Solid Foundation

Got your shopping list? Now discover how to install your insulation and optimise the weight of your timberwork in our structural guide.

Read the Structure & Insulation Guide →

Frequently Asked Questions

Should I calculate insulation based on the external or internal dimensions?

You should always use the usable internal dimensions (the rear cargo area). A vehicle's external dimensions (often referred to as L2H2, L3H2, etc.) include the bodywork, bumpers, and driver's cab, which would significantly overestimate the amount of material you need to buy.

Why does the calculator add a safety margin?

A van isn't a perfectly square box. The walls are curved, and there are wheel arches, structural ribs, and complex corners. These cuts inevitably create offcuts that cannot always be reused. As a general rule, allow a 10% margin for flexible insulation and 15% for rigid sheet timber.

What thickness of plywood should I choose for the floor?

The subfloor will support the entire weight of your conversion (furniture, water tanks, and living space). You should use robust plywood at least 12mm to 15mm thick (ideally lightweight poplar, okoumé, or birch ply). Avoid OSB or MDF, as they are far too heavy and swell when exposed to moisture.

What thickness of timber should I use for the walls and ceiling?

For the walls and ceiling, the aim is to keep overall vehicle weight down. Thin 5.5mm or 9mm plywood, or lightweight tongue-and-groove cladding, is standard. As the timber is fixed into battens, it will naturally follow the van's body contours without excessive force.

How many square metres does a roll of Armaflex contain?

It depends on the thickness you buy (the carton size remains standard). A box of 19mm Armaflex contains a 6m² roll. A 13mm box contains 8m². A 6mm box (specifically for thermal bridges) contains 15m².

Should I deduct my windows from the area to be insulated?

Yes, absolutely! If you have side windows, rear glass, and roof vents, they can easily account for 2 to 3m² of surface area. Failing to deduct them could mean buying an unnecessary extra roll of Armaflex.

What is the 6mm Armaflex recommended by the calculator used for?

The 6mm (or 9mm) is used to eliminate thermal bridges. The van's internal structural metal ribs protrude into the living space. You cannot fit 19mm insulation over them without losing too much interior space or creating lumpiness. Instead, use thin, flexible 6mm insulation to seal these metal ribs.

How do I calculate the amount of timber battens I need?

Battens create the framing grid that your wall and ceiling lining fix into. As a general rule, allow around 1.5 to 2 linear metres of softwood battens for every square metre of wall and ceiling area. Always order a modest buffer for cutting errors.

Do I need to insulate the floor to the same thickness as the ceiling?

Not necessarily. Heat rises, making the ceiling critical for heat loss in winter and solar heat gain in summer. The floor is less exposed. Many builders use 19mm Armaflex on the ceiling, but opt for thinner 10mm to 25mm XPS (extruded polystyrene) or PIR insulation board under the floor to maximize interior head height.

Can I return any leftover materials?

For timber cut to size or modified, returns are generally not possible. For Armaflex, if the box is sealed and undamaged, most UK specialist suppliers accept returns within 14 to 30 days, though return shipping fees for large boxes will be your responsibility. Calculating accurately upfront avoids this headache.