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Supplied floors and rafts
Some floors do not have a layer stack you can build from products. A proprietary insulated raft (an engineered pod-and-rib slab system) has an R-value that depends on the specific geometry of the job, and the manufacturer determines it. Thermly has a dedicated path for these: you enter the supplied R-value and record where it came from.
Why a raft's R-value is per-project
A raft slab's thermal resistance depends on its area-to-perimeter ratio and its rib and pod geometry, both specific to your building. There is no single catalogue R-value that is correct for every job. Manufacturers publish a calculator (or an H1/VM1 determination) that produces the R-value for your particular floor's dimensions and configuration.
So Thermly does not store a raft R as a catalogue constant. Instead you run the manufacturer's calculator for your floor, then enter the result with its source. This keeps the number honest and traceable to the determination it came from.
Entering a supplied floor
For a proprietary raft, open the supplied-floor path ("Proprietary insulated raft - supplied R-value") and complete:
| Field | What to enter |
|---|---|
| Raft system | Pick the manufacturer system from the list (or "Other / not listed"). |
| Manufacturer / system | The system name, for example "MAXRaft". |
| Construction R-value (m²·K/W) | The R-value from the manufacturer's determination for this floor. |
| Source document / determination reference | Where it came from, for example "[manufacturer] R-value calculator output (job 12345), 2026-06-22". |
| How was it determined? | Manufacturer R-value determination, H1/VM1 Appendix E calculation, ISO 13370, or another basis. |
If the selected system publishes a calculator, Thermly shows a "[system] calculator →" link that opens it in a new tab. Run it for your floor's area-to-perimeter and configuration, then enter the result - it is valid only for the geometry you computed.
Thermly requires both the manufacturer and the source document: "A supplied floor R-value must record its manufacturer and source document (E.1.1.1(b))." That is what makes the value defensible on the consent record.
How it appears on the report
A supplied floor is used verbatim - Thermly does not recompute it - and the basis is stated clearly. The wizard's summary shows:
- "Whole-floor construction R: R[value] (manufacturer-supplied, used verbatim)"
- "Source: [your source document]"
- "Basis: H1/AS1 Appendix E, Paragraph E.1.1.1(b) - not the Appendix E performance tables (E.1.2.1)"
The generated report then carries an always-on disclosure that the value was externally determined per Paragraph E.1.1.1(b) - naming the manufacturer and source document, and stating that it is not a Thermly engine calculation and not derived from the Appendix E performance tables - so a reviewer can see exactly where it came from.
A sense-check, not a cap
Thermly does not alter a supplied R-value, but it will flag one that looks physically implausible. A value above R6.5 - a deliberately generous ceiling, set just above the Appendix E tables' maximum - raises a caution on both the calculator and the report (it catches a decimal slip, for example R28.7 typed for R2.87). The value is used as entered; the caution simply asks you to confirm it.
Standard slabs and generic rafts
A plain slab-on-ground, or a generic system used generically (standard RibRaft, Expol Tuff Pods, a plain waffle pod), is not a supplied-R case. Those use Thermly's slab wizard, which looks the R-value up from the floor's area-to-perimeter ratio, edge insulation and cladding per H1/AS1 Appendix E (Paragraph E.1.1.1(a) and the performance tables). See How Thermly calculates compliance.