How to compare floor EPDs

At a glance

All seven must pass. RICS references are to Version 3 of the 2nd edition (August 2024). EN 15804 itself was not read.

Can you compare them at all?

You can compare the embodied carbon of two floors, but only when two numbers are the same quantity. A headline figure for an oak floor and one for a stone floor are usually not. They may be given per square metre of installed floor or per tonne of stone, they may cover the factory gate only or the whole life, and they may treat the carbon stored in timber differently. Put two such numbers in a table and the table will look rigorous and be wrong.

The risk is a reputational one. A client or a bid team will repeat your table, and the Competition and Markets Authority’s Green Claims Code expects comparisons to be fair and meaningful (see the sustainability paperwork sheet). This sheet therefore gives the method and a blank worksheet, and it does not give per-square-metre values for timber, stone, terrazzo or resin. We have not collected the EPDs that would justify them, and a number from another project cannot stand in for the product you are specifying.

Start with the seven checks in the table above. They are cumulative: one that fails is enough to stop a comparison. The sections that follow explain the three that cause most trouble: the modules, the biogenic carbon, and transport.

Modules: compare only what both declare

The RICS professional standard on whole life carbon assessment (2nd edition, effective from 1 July 2024; Version 3, August 2024, was the text read) groups a building’s life into modules. A1 to A3 is the product stage, covering extraction, transport to the factory and manufacture. A4 and A5 are the construction stage: transport to site, then installation, including waste. B is the in-use stage, C is end of life, and D covers benefits and loads beyond the system boundary and is reported separately. The drawing shows the three scopes a carbon figure can cover.

The one floor EPD we read for the earlier sheet declared A1 to A3 and some later modules; an EPD marks those it does not declare as ‘MND’, as the sheet on reading an EPD explains. Many EPDs concentrate on the product stage. Upfront carbon in the RICS standard means A1 to A5. A figure that stops at A3 does not include the lorry from the quarry or the factory to your door, or the offcuts you throw away on site. Two floors can swap places in a ranking when A4 and A5 are added.

The rule that follows is simple. Write down the modules each figure covers and compare only the modules both cover. If one EPD declares A1 to A3 and the other A1 to A3 plus C, compare A1 to A3 with A1 to A3 and say that is what you did.

Declared unit: what ‘per m²’ hides

The declared unit is the quantity the results are given for. The EPD we read for the earlier sheet used 1 m² of installed flooring, and that is a common unit for floors, but not the only one: stone is often described per tonne or per cubic metre and a slab EPD may stop at the slab. To compare, you need the same unit and the same function. A floor is more than its wearing surface: stone is bedded on a mortar or adhesive layer, and a glued timber floor needs an adhesive, and perhaps a primer. Whether those layers are in the declared unit depends on the EPD. Our reasoning is that you should add them in explicitly, from the build-up (see floor build-up heights), and say so.

Thickness also matters. A figure per square metre belongs to the thickness it was declared for; an EPD that covers a range of thicknesses should say how to scale between them. A 15 mm board and a 20 mm stone slab have different masses per square metre, and so a different transport load. If the EPD gives results only for the thinnest and thickest board of a range, a board in between has to be interpolated by the rule the EPD states, not by guesswork.

Finally, durability is not in a per-square-metre figure for the product stage. A floor that is replaced twice in a hotel’s life carries three times the product-stage impact. RICS asks for the assessment period to be stated and for replacement to be handled in the in-use stage; this sheet does not read the reference service life of any floor, so it does not rank floors by life.

Timber and biogenic carbon

Timber takes carbon dioxide out of the air as it grows, and the carbon stays stored in the wood while the floor is in use. The RICS standard says that sequestered carbon in timber may be counted as a removal only if the timber is sustainably sourced, for example through FSC or PEFC certification or equivalent, or sourced from countries that account for forest carbon under Article 3.4 of the Kyoto Protocol and report increasing forest carbon pools (section 4.11.1). Timber that cannot show this counts no removal. Its biogenic carbon, when it is released, is treated as a land-use emission like a fossil one.

The standard also says that biogenic carbon must be reported separately when you report only upfront carbon (glossary, and section 4.11.1), and that, over the whole life, removals in A1 to A3 should be balanced by emissions at end of life in C3 and C4. In practice the headline in an EPD can look very low or even negative for a timber floor in A1 to A3 once the stored carbon is netted off, and a stone floor has no such credit. The RICS standard itself warns about this: using more biomass purely to reduce the carbon number in A1 to A5 is a perverse incentive.

So ask three things of a timber EPD. Does the headline figure include the stored carbon, or is it reported apart? Is the timber certified, so the removal may be counted at all? And what happens to the floor at end of life in the scenario (C3 and C4), because the balance depends on it. If two floors are being compared, show the figure with and without the biogenic carbon, and say which one the client asked for. This sheet does not read EN 15804 itself, so the exact indicators an EPD reports for biogenic carbon should be checked in the document.

Adding transport (A4): imported stone, UK timber

Module A4 is the transport from the factory gate to the site. The RICS formula for it (section 5.1.3) is the mass of the product times the distance times a carbon conversion factor for the outward journey, with the return journey added using an empty-running factor. It does not include the journey to the factory, which is already in A1 to A3. For a UK project in early design, when the supply route is not known, RICS gives default transport scenarios in its Table 17. Examples from that table: nationally manufactured goods such as structural timber, 120 km by road; European-manufactured goods such as cross-laminated timber, 1,500 km by road and 100 km by sea; and globally manufactured goods such as specialist stone cladding, 500 km by road and 10,000 km by sea. The standard says to allocate each product to a category with the design team.

Those are scenarios for early design, not the route of any floor. For a specified floor you should use the real origin and route, which means asking each supplier, in writing, where the product is cut, finished and loaded, and by what mode. Imported Italian stone and UK-grown oak differ in distance and in mass per square metre, and A4 is proportional to both. We have not read the conversion factors that RICS points to, so this sheet does not calculate kilograms of carbon dioxide for either: the worksheet at the end asks for the inputs, and your assessor supplies the factors.

For a floor that is laid on a bed or an adhesive, remember that A4 applies to every layer, not just the visible one.

Specific, collective or generic data

RICS ranks carbon data for the product stage. For a construction or post-completion assessment, the first choice is an EPD from the chosen manufacturer that covers the actual product used. Failing that, a collective EPD from all the members of a UK trade association, then one from a representative selection of producers; where a product is commonly imported, a collective EPD with a wider geographical basis; then generic data from a geographically relevant database. RICS names the Built Environment Carbon Database (BECD) as a source of generic UK data. Collective EPDs often represent an average of a group of products, and RICS says they should describe what they represent and the variation across the range if it is significant, normally more than 10 per cent either way.

That ladder explains what the market looks like for floors. Stone Federation Great Britain’s page links ten EPDs for UK stone products, mostly masonry, walling or paving, and states that an EPD is usually valid for five years; it gives no carbon figures and says nothing about how to compare them. We did not find a terrazzo or resin floor EPD for this sheet. If the only data for one floor is a generic value and for another a verified product EPD, you are not comparing like with like, and the honest answer to the client is that the two floors have data of different quality. RICS also asks for the data source to be stated in a report.

Different programme operators and product category rules (PCRs) can produce declarations that are not directly comparable. Check the PCR named in each EPD. We have not read any programme operator’s rules, so we cannot tell you which pairs of operators are compatible; ask the assessor.

Answering the client, and the worksheet

When a client asks which floor has the lower carbon, a safe answer has four parts. Say which products, with their EPDs. Say which modules and which unit you compared. Say whether biogenic carbon is shown separately. And say what was assumed for transport, with the route. Where the data is not comparable, say that too, and offer what can be said: the supplier’s own figure for its product, labelled with its scope, and a recommendation that the project’s carbon assessor models both floors with the same method.

Do not use phrases such as ‘low carbon floor’ or ‘carbon negative’ unless a verified document supports the exact claim in the exact context. Keep the EPDs, the date you checked each, and your worksheet in the project file. For the wider set of documents a tender may ask for, see the tender sustainability sheet, and for furniture and lighting data, embodied carbon data for FF&E.

Comparison worksheet

[Supplier] is to provide, with the tender return, a verified EPD for the exact product offered, to BS EN 15804:2012+A2:2019, stating programme operator, registration number, valid-until date, declared unit [1 m2 installed] and the modules declared. Modules A1 to A3 are required as a minimum; [A4 and A5 / C and D] where available. For timber, the chain of custody claim as clause [FSC and PEFC clause reference].

Where a carbon figure per [m2] is quoted, it is to state the modules it covers, whether biogenic carbon is included or reported separately, and the product thickness, species or quarry, and finish to which it applies. Figures for different scopes are not to be compared.

[Supplier] is to state the place of manufacture and finishing, the mass per [m2] as delivered, and the transport mode and distance to the site, so that module A4 can be assessed by [the project carbon assessor].

[Client target, kgCO2e per m2] applies to modules [A1 to A5] as assessed by [assessor]. A supplier figure is not compliance until the assessor confirms the same modules and unit.

Standards and sources

• RICS: Whole life carbon assessment for the built environment, 2nd edition: Version 3, Aug 2024; read 7 Nov 2026. Confirm current.
• BS EN 15804:2012+A2:2019: BSI: Current, under review (30 Sep 2021); listing only.
• Stone Federation Great Britain: natural stone EPDs: ten EPD links; validity statement; read 7 Nov 2026.

Questions we are asked

Can I compare an oak floor EPD with a stone floor EPD?

Only if they share the standard edition, the declared unit and function, the modules and the biogenic carbon treatment, and both cover the product you are specifying. Often they do not. If they differ, compare only the modules both declare, and say so.

Why does a timber floor sometimes look very low in carbon?

Because carbon stored in the wood can be netted off in the product stage. RICS says sequestered carbon may be counted only for sustainably sourced timber, must be reported separately for upfront carbon, and is balanced by end-of-life emissions over the whole life. Show the figure with and without it.

Is A1 to A3 enough for a client report?

It is the product stage only. For an upfront figure RICS uses A1 to A5, so transport to site and installation are missing from an A1 to A3 figure. State the scope on every number.

How do I add transport for imported stone?

Use the real origin, the mass per square metre as delivered and the route, then apply your assessor’s conversion factors with the RICS A4 method. In early design RICS gives default scenarios (Table 17) by how far a product travels. Do not mix a real route for one floor with a default for the other.

Do terrazzo and resin floors have EPDs?

We did not find floor EPDs for either for this sheet, and we have not looked at databases. Ask each supplier; where none exists, say that the data is generic or unavailable.

Does the studio hold EPDs for its floors?

This sheet says nothing about what the studio or a partner workshop holds. Ask for the EPD of the exact product at enquiry; the studio coordinates manufacture through partner workshops, so the document depends on the product and the workshop.