# Codes and rules: finding and following the requirements that apply

> Rules and scope, safety, accessibility, comfort and services, and approvals: finding the requirements that apply and carrying them to completion.

Source: https://guide.rayon.design/knowledge/foundations/codes-and-rules · Foundations · Updated 2026-10-18

© 2026 Rayon. Quote short excerpts with a link to the source page. Full terms: https://guide.rayon.design/about

## Introduction

Every interior answers to rules that protect the people who use it. This page shows how to find which ones apply, design to them, and carry them through to completion.

## Rules and scope

Establish which requirements apply before designing.

Start by telling apart three kinds of document. **Regulations** are law: building codes and the rules that enforce them. **Technical standards** describe how to test, size or build something, and become mandatory when a regulation cites them. **Guidance** explains one accepted way to comply. Then pin down the project: where it is, what the building is used for, how many people will be in it and what work is proposed. These decide which codes apply, which editions and which local amendments. In a renovation, investigate what is already there, including the structure, the services, any protected features and possible hazardous materials such as asbestos. Alterations, and above all a change of use, can trigger requirements that the existing building never had to meet.

*Interactive diagram:* One tenancy fitted out as an office, then as a restaurant, with the checks each use brings and the ones that change.

*The same tenancy as an office, then as a restaurant. The new use brings new checks and changes others.*

Work through these steps before drawing anything. They establish which rules apply, which editions and amendments are in force, and what the existing building and the proposed changes will demand. Record the answers as you go: they become the reference every later decision is checked against.

1. 01**Locate**Identify the jurisdiction and the authorities responsible for approvals.
2. 02**Classify**Record the existing and proposed use, the occupant capacity and the scope of work.
3. 03**Survey**Identify existing constraints and the specialist investigations needed.
4. 04**Check triggers**Investigate the requirements that the proposed changes bring with them.
5. 05**Record**List the applicable sources and editions, and the questions still open.

## Safety

Prevent everyday injuries and enable safe escape.

Safety covers two situations. In an emergency, people must reach a place of safety: escape routes, exits, travel distances and widths, and the fire and smoke separation that protects them, including doors, finishes and the services that pass through fire-resisting walls. Every day, people must move around without harm: stairs and changes in level, guarding at drops, glazing people might walk into, slippery floors and collision risks. Furniture changes the usable width of a route, so test layouts with chairs pulled out and doors open. A product is only as good as its application: a fire-rated door or a slip-resistant tile performs as tested only within the complete assembly it was tested in. See [circulation](https://guide.rayon.design/lexicon/circulation) and [clearance](https://guide.rayon.design/lexicon/clearance).

*Interactive diagram:* One office floor read for everyday hazards, then for escape and fire separation, then with a cabinet moved into the escape route.

*One floor read for everyday hazards, then for escape, then with a cabinet pushed into the route.*

Review each layout with these checks, on the [plan](https://guide.rayon.design/lexicon/plan) and again with the furniture in place, doors open and chairs pulled out. Repeat them whenever the layout changes: a moved partition or a new piece of storage can narrow a route or block an exit.

1. 01**Trace escape**Check routes, travel distances, widths and exits against the applicable requirements.
2. 02**Test movement**Account for furniture in use, door swings and changes in level.
3. 03**Review hazards**Check stairs, guarding, glazing and floor surfaces.
4. 04**Check separation**Coordinate fire-resisting walls, doors and service penetrations.
5. 05**Verify [specifications](https://guide.rayon.design/lexicon/specification)**Confirm the required performance of finishes and assemblies.

## Accessibility

Enable people with different disabilities to use the space.

Treat accessibility as a continuous journey: arriving, entering, moving around, using the facilities, receiving information and leaving safely, including in an emergency. Design for mobility, visual, hearing and cognitive needs, not only for wheelchair users: clear floor space alone does not make a space accessible. Identify the obligations that apply. In the United States these are the **ADA Standards for Accessible Design**, issued under the Americans with Disabilities Act, together with state and local codes, which can be stricter. Elsewhere the equivalents are national and local provisions, such as Part M of the Building Regulations in England, the Equality Act 2010 in the United Kingdom, or EN 17210 in Europe. Then decide, with the client, where the design should go beyond the legal minimum: inclusive design serves far more people than any rule requires.

*Interactive diagram:* A wheelchair user's journey from the entrance to reception, a workstation and the accessible toilet, with what each stop needs.

*One journey through an office: at each stop, a different requirement comes into play.*

Walk the plan as a disabled visitor would, from the street to every space they need and back out in an emergency. Test each step for people with mobility, visual, hearing and cognitive needs, not only for wheelchair users.

1. 01**Identify**Establish which accessibility rules apply to the project and to the alterations.
2. 02**Connect**Trace an accessible route to the spaces and amenities people need.
3. 03**Test operation**Check doors, manoeuvring space, controls, seating and work surfaces.
4. 04**Check facilities**Review toilets, washing areas and other amenities against the relevant requirements.
5. 05**Communicate**Consider readable signage, [contrast](https://guide.rayon.design/lexicon/contrast), lighting, and audible and visual information.
6. 06**Review evacuation**Coordinate provisions for occupants who may need assistance to leave.

## Comfort and services

Provide healthy indoor conditions and coordinate essential systems.

Codes also set the conditions people live and work in: ventilation, lighting, acoustics, thermal comfort and, increasingly, energy use. The guide covers each in its own page: [Light](https://guide.rayon.design/knowledge/foundations/light), [Acoustics](https://guide.rayon.design/knowledge/foundations/acoustics) and [Temperature](https://guide.rayon.design/knowledge/foundations/temperature). In wet areas, add drainage, waterproofing and protection against scalding from hot water. Interiors and services meet everywhere: partitions change how air moves, ceilings carry lights, detectors and sprinklers, and joinery can hide the equipment that needs servicing. Bring in specialists early, compare the layouts drawn by each of them, and keep every control, valve and access panel reachable: an attractive layout must also let the building work.

*Interactive diagram:* A room with its ceiling void open: light and air, then the services, then a partition and a cupboard that get in their way.

*A room with its ceiling void open: light and air, then the services, then the conflicts a new partition and a cupboard create.*

Coordinate the interior with the services before the design is fixed, when changes are still cheap. Lay each specialist's drawings over your own, look for clashes between partitions, ceilings, joinery and equipment, and keep every point that needs maintenance within reach.

1. 01**Review conditions**Identify the applicable indoor-environment and energy requirements.
2. 02**Check layouts**Consider how room depth, partitions and occupancy affect light, air and sound.
3. 03**Resolve wet areas**Coordinate fixtures, drainage and moisture protection.
4. 04**Overlay services**Compare the ceiling, lighting, electrical, ventilation and fire-safety layouts.
5. 05**Preserve access**Keep equipment, controls and maintenance points accessible.

## Checks and approvals

Carry requirements from design decisions through to completion.

Keep a simple record of each requirement: where it comes from and how the design responds. Building-control approval, which checks compliance with the building regulations, is separate from planning permission, which controls use and appearance, and from other permissions such as landlord, heritage or licensing consents. Agree who prepares, coordinates and checks each requirement, who submits what and when, and who attends which inspections. Collect evidence for products and assemblies, and recheck every substitution and site change: an equivalent product is not equivalent until its evidence says so. At the end, keep the completion records and the operating information, so the finished interior can be used and maintained as intended.

*Interactive diagram:* One fire-resisting door followed from the plan to its specification, installation and completion evidence, then a substitution that resets the checks.

*One fire-resisting door, from the plan to its completion evidence. A substitute leaf resets every check.*

Carry each requirement from the first drawings through to the finished interior. Make sure every decision has an owner, every product has its evidence, and every change on site is checked again before it is built.

1. 01**Assign**Identify who prepares, coordinates and checks each requirement.
2. 02**Document**Link each requirement to drawings, details and specifications.
3. 03**Submit**Establish the permissions required and their timing.
4. 04**Recheck changes**Review substitutions and site changes before they are carried out.
5. 05**Close out**Collect inspection records, certificates, as-built information and operating instructions.

## Questions

What people ask most about codes and rules.

### What is a certificate of occupancy?

It is the document the local building department issues to confirm that a building, or a space within it, complies with the codes and can be occupied for its intended use. It is usually needed after new construction, after a major renovation and whenever the use changes, for example when an office becomes a restaurant. Without it, a tenant may not be allowed to open.

### What is a building permit, and does an interior project need one?

A building permit is permission from the local building department to carry out specific work, followed by inspections. Interior projects usually need one when they move or remove walls, alter the structure, change the layout of rooms or exits, or add or alter electrical, plumbing, gas or ventilation work. Painting, new flooring and like-for-like cabinet replacements often do not. The rules vary by place, so check with the local department before the design is fixed.

### What does ADA compliant mean?

It means a space meets the 2010 ADA Standards for Accessible Design, the technical rules under the Americans with Disabilities Act. They apply to public accommodations, commercial facilities and state and local government buildings in the United States, including shops, restaurants, offices and hotels. Private homes are generally not covered, although state and local codes may add their own requirements.

### What are the requirements for an ADA-compliant bathroom?

Under the 2010 ADA Standards, a single-user toilet room needs a 60 inch turning circle or a T-shaped turning space, a door with at least 32 inches of clear width, a toilet centred 16 to 18 inches from the side wall, grab bars on the side and rear walls mounted 33 to 36 inches above the floor, a sink no higher than 34 inches with knee space below, and a mirror whose reflecting surface starts no higher than 40 inches. Controls must work with one hand, without tight grasping or twisting.

### What is the maximum slope of an ADA ramp?

The 2010 ADA Standards allow a running slope of no more than 1:12, which is one inch of rise for every 12 inches of run. Each run may rise at most 30 inches before a level landing, the cross slope may not exceed 1:48, and a ramp that rises more than 6 inches needs handrails on both sides. A gentler slope is easier for everyone.

### What is the ADA counter height?

Sales and service counters need a section at least 36 inches long and no higher than 36 inches above the floor, so a wheelchair user can approach and be served. Work surfaces and dining surfaces for public use should be 28 to 34 inches high, with [knee clearance](https://guide.rayon.design/knowledge/foundations/space) below.

### What is the minimum ADA door width?

A door must give at least 32 inches of clear width, measured with the door open at 90 degrees between the face of the door and the opposite stop. [Thresholds](https://guide.rayon.design/lexicon/threshold) may be no higher than half an inch, bevelled, and the door needs clear manoeuvring space on both sides and hardware that works without tight grasping.

### What is an egress window?

An egress window is a window large enough for people to escape through and for firefighters to enter. In the United States, the International Residential Code requires one in every sleeping room and in habitable basements, with a net clear opening of at least 5.7 square feet, at least 24 inches high and 20 inches wide, and a sill no more than 44 inches above the floor. A basement bedroom without one cannot legally be called a bedroom.

### What is the standard height of a handrail?

Both the International Residential Code and the International Building Code set stair handrails at 34 to 38 inches above the stair nosings. In England, Approved Document K sets 900 to 1000 mm. Handrails must be continuous and easy to grip, and accessible routes often need one on each side.

### What is the building code for stairs?

Under the International Residential Code, a stair in a home may have risers of at most 7¾ inches and treads of at least 10 inches, with at least 6 feet 8 inches of headroom. The International Building Code is stricter for other buildings: risers of 4 to 7 inches and treads of at least 11 inches. Keep every riser and tread in a flight the same size: uneven steps cause falls.

### What is a fire-rated door?

A fire-rated door is a complete door assembly, including the leaf, frame, hinges, closer, seals and any glazing, that has been tested to hold back fire for a set time, such as 20, 60 or 90 minutes. It carries a label, must close and latch on its own, and only performs as tested when installed as tested. Changing any part, from the hinges to a vision panel, can void the rating.