# Building Assemblies & Specs

> How architects specify building assemblies — fire-resistance-rated walls and floors, R-values and U-factors, and STC acoustic ratings — with typical build-ups and where the authoritative tested listings come from.

- Canonical: https://harth.build/resources/assemblies/

Architects don't specify materials in isolation — they specify **assemblies**: layered build-ups whose fire, thermal, and acoustic performance is measured as a system. A rated wall is only rated when built exactly as the tested listing describes; a stud, a layer of gypsum, and an insulation type are meaningless numbers until they are assembled and tested together.

These pages explain the ratings architects put on drawings and in specifications — fire-resistance ratings, R-values and U-factors, and STC — and show typical build-ups that achieve them. Every specific number here is **illustrative** and meant to build intuition. For a project, the governing values come from a tested assembly listing (UL Product iQ, the GA Fire Resistance Design Manual) or a manufacturer's submittal, referenced by design number.

_Prepared by Harth as generated collection navigation. Evidence and review scope are recorded on each linked page._

## Pages

- [Fire-Rated Wall Assemblies Explained (1-Hour vs 2-Hour)](https://harth.build/resources/assemblies/fire-rated-wall-assemblies-explained.md)
- [Understanding R-Value and U-Factor](https://harth.build/resources/assemblies/understanding-r-value-and-u-factor.md)
- [STC Sound Ratings for Walls](https://harth.build/resources/assemblies/stc-sound-ratings-for-walls.md)
- [Typical Exterior Wall Assemblies (Layer by Layer)](https://harth.build/resources/assemblies/typical-exterior-wall-assemblies.md)
- [IBC Construction Types Explained: Type I, II, III, IV & V](https://harth.build/resources/assemblies/ibc-construction-types-explained.md)

![Labeled wall-assembly cutaway diagram: Building Assemblies & Specs](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/assemblies/index/diagram-1344.webp)

*How architects specify building assemblies — fire-resistance-rated walls and floors, R-values and U-factors, and STC acoustic ratings — with typical build-up…*

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