How to Write a Custom Unit Requirements Brief

Why a brief is more useful than a feature list

A feature list records what someone wants to add. A requirements brief explains why, under what conditions, and how the result will be judged. That distinction matters when a request involves a container or trailer because an apparently simple option can affect space, structure, access, services, transport, approvals, and future maintenance. “Add two windows” is incomplete without knowing who uses the space, what those windows need to accomplish, whether privacy matters, and where the unit will sit. A useful brief enables a supplier to identify unknowns rather than guessing at the customer's intent.

Think of the document as a shared starting point—not a technical design, engineering approval, code determination, or promise of availability. The brief helps the customer, supplier, designer, site owner, and qualified reviewers discuss the same use case. It should distinguish facts from assumptions and unresolved questions. If a dimension is estimated, label it. If someone suggested a feature without checking feasibility, mark it as an idea. That simple discipline reduces the chance that a preliminary conversation becomes an unintended commitment.

Begin with a short project statement: “We need a [type of space] for [users or contents] at [site] to support [work or storage task] during [expected period].” Add one sentence about the primary measure of success. Examples might be retrieval of particular items without moving others, a quiet place for dispatch work, or weather-protected storage near a maintenance route. Keep the statement focused on outcomes rather than a preferred modification. Then add a list of known constraints and a list of questions still requiring confirmation.

For the provider's current category descriptions, review the customized solutions page. If the use includes office and inventory functions, the office-and-storage category may also inform the conversation. Neither category page should be treated as a commitment to a particular layout or option; ask what is actually offered and can be considered for the project.

Describe users, occupancy, and tasks

If people will enter or work in the unit, describe their activities before choosing a layout. State the expected number of users at typical and peak times, the length and frequency of visits, and whether the activity is sitting, standing, handling materials, operating equipment, meeting, or another task. Identify if people need to communicate, concentrate, see a work surface, access records, or move between areas. Avoid using a vague room label such as “office” as a substitute for the actual function.

If the unit is for storage, inventory should be organized by physical characteristics and retrieval patterns. List representative item dimensions, approximate quantities, weights if known, packaging, arrival method, and access frequency. Identify unusually long, fragile, dense, dusty, temperature-sensitive, or regulated contents as issues requiring specific review. Note which objects need to be grouped together and which should be kept apart. The aim is not to prescribe an installation without expertise; it is to make the constraints legible to people who can assess the design.

Describe the workflow as a sequence. For example: a delivery arrives, is checked, placed into a storage zone, retrieved by one worker, and moved to a work area. Where does a cart travel? Where must a person stand while a door is open? Does the user need both hands free at an entrance? Is there a handoff between two teams? What activity takes the most time or creates the most congestion? A simple annotated sketch often reveals that the critical need is a clear route rather than more floor area.

If people and materials share a space, state how they interact. Can deliveries pass through the same doorway as staff? Does a task produce noise, dust, heat, odor, or vibration that affects a desk area? Is there a reason to separate functions physically or by operating rules? A combination unit can save footprint but may create circulation conflicts or expose work areas to storage activity. Consider the office-and-storage category as a comparison, then request the exact proposed arrangement rather than assuming a standard split.

Inventory equipment and utility demands

Create an equipment schedule that includes each intended device, its purpose, dimensions, nameplate or manufacturer data if available, operating hours, expected simultaneous use, and any special connection or environmental needs. Include workstations, lighting, chargers, appliances, pumps, heaters, ventilation equipment, network devices, and tools. The list helps a qualified person assess electrical demand and layout. A phrase such as “a few outlets” does not state what will be plugged in or whether multiple devices will run at the same time.

Separate utility needs from the design solution. Say, for example, that users require a comfortable environment during stated hours, rather than deciding without review that a particular heating or cooling system is appropriate. Identify known site services and their source: electrical service, water, drainage, communications, or none. Record whether a connection point is physically close, but do not infer that it has suitable capacity. Ask who verifies service compatibility, specifies equipment, performs installation, and arranges any required inspection.

For electrical work, record all loads and site information, then have qualified electrical personnel determine the appropriate design and installation. OSHA’s general-industry electrical standards set out requirements for workplace electrical systems in their applicable context; they do not demonstrate that a proposed custom unit or connection complies. Make responsibility explicit: who provides a load review, connection plan, electrician, permit application, inspection, and operating instructions?

Ventilation and indoor conditions deserve similarly specific questions. Describe expected occupancy, hours, activities, heat sources, possible contaminants, cleaning products, and any processes that may produce moisture or fumes. Do not select a fan by intuition or assume that a window resolves air-quality or thermal needs. Identify whether a specialist must determine ventilation rates, equipment, controls, and commissioning for the actual use. The technical reviewer should be told about the actual process, not simply that the unit needs to “breathe.”

If the brief involves people with varied mobility or sensory needs, describe the user journey and ask for a qualified accessibility review. The Access Board’s guide to entrances, doors, and gates discusses relevant design elements under the ADA Standards. A link to that material is not a finding that any planned arrangement meets applicable requirements. Record the approach route, entry, door use, interior circulation, work positions, and service counter needs for review against the project and jurisdiction.

Set out site, movement, and environmental constraints

Give the exact proposed address and a marked site plan if available. Identify the intended position, door orientation, property boundaries, nearby buildings, fences, trees, overhead lines, slopes, drainage paths, paved or unpaved surfaces, gates, turning areas, and vehicle traffic. A short site walk with photographs can supplement a drawing: take views from the road, each turn, the planned route, and the proposed placement location. Note the date and conditions, because surface firmness and seasonal access can change.

State whether the unit is intended to stay in one place or move during use. If movement is anticipated, describe who needs to move it, how often, between which sites, and what contents might remain inside. Do not assume that a modified unit can be transported in the same way as its original configuration. Added openings, fittings, rooftop equipment, or projections may affect handling or travel. Ask the supplier to identify the transport assumptions and the information it needs to review route and placement feasibility.

Include local conditions relevant to use: exposure to wind, snow, dust, sun, temperature swings, or nearby operations. This is not a request for the customer to design structural, weather, or ventilation systems. It is context for a qualified reviewer. Distinguish known observations from engineering assumptions. “The west side gets afternoon sun” is useful; “the unit will be safe in any storm” is not a defensible requirement. Ask who assesses site-specific conditions and what evidence or design input is needed.

The current service areas page helps establish where Mobile-Stor lists service coverage, but a listed area cannot guarantee delivery to an individual site. Share the location, route, access limits, proposed unit configuration, and likely timing with the provider. The existing delivery site preparation guide helps organize the basic site information; custom projects may need additional review of altered dimensions and handling.

Rank requirements and make tradeoffs explicit

Divide needs into three groups: mandatory, preferred, and optional. A mandatory item should have a reason and a test for acceptance. For example, “the most frequently used item must be retrievable without relocating the large equipment” is testable against a layout. “Large windows would be nice” is a preference until its benefit and effects are evaluated. Use a separate list of exclusions—things that must not happen, such as placing confidential work in view of a public entrance or blocking a designated route.

Add a priority scale if requirements compete. For each item, indicate the consequence if it is not met, who made the decision, and whether a substitute would be acceptable. This allows a designer to compare options honestly. If an additional door reduces wall area needed for shelving, the team can revisit which requirement has greater value rather than arguing from preference. A good brief allows alternatives without silently weakening the outcome.

Identify the constraints that cannot change: site footprint, delivery access, available service, schedule milestone, intended duration, budget range if the customer chooses to share one, and approval conditions. Make clear which are confirmed and which are estimates. If a date depends on approvals or a project phase, say so. Do not request a guaranteed schedule when critical inputs are still unknown; ask what events govern timing and what decisions are needed by when.

Assign questions to the right people

For each unresolved topic, name the person or organization expected to answer it. The supplier can clarify its actual product options, current availability, scope, and information needs. A structural professional may need to assess an opening or attachment. An electrician evaluates electrical design and connection. The local authority determines which local approvals apply. A property manager may control access or site rules. A project lead coordinates those decisions. Avoid assigning all technical decisions to a sales contact merely because that person is the first point of contact.

Prepare questions in categories. For the supplier: What unit and configuration are being proposed? Which dimensions are verified? What modifications are within scope, and which are not? What is included, excluded, or subject to confirmation? What information is needed to assess delivery? For qualified reviewers: What drawings, calculations, site data, or equipment schedules are required? For the authority: Which approvals or code reviews apply to this use and location? For the installer: Who completes the work and provides documentation?

Record answers with a date, name, and any limitations. “Probably acceptable” is not a final approval. “Supplier will confirm” is an action, not an answer. Mark each item open until the responsible person provides the needed evidence. For decisions that depend on local interpretation, ask the relevant authority directly rather than relying on a generalized article, neighbor's experience, or a different jurisdiction’s past project.

Turn the brief into a proposal checklist

Attach the brief to a request for an itemized written proposal. Ask for a dimensioned drawing and a description of the base unit, proposed modifications, equipment, utility boundaries, delivery and placement assumptions, schedule dependencies, exclusions, and any owner-provided work. Identify who prepares technical drawings, who obtains approvals, who supplies and installs utilities, who arranges inspections, and what documentation will be delivered. Ask for each unresolved assumption to be listed rather than buried in correspondence.

Before evaluating price, verify that the proposal responds to the required functions. Ask how each mandatory criterion is met and whether the drawing shows it. Compare allowances, exclusions, installation boundaries, assumptions, and possible change costs. Request a revision when written scope and drawing disagree. If the proposal substitutes a feature, evaluate the substitution against the original outcome rather than accepting that it sounds similar.

Preserve version control. Label the brief, drawing, and proposal with dates and revision identifiers. Keep a comment log and obtain confirmation when a change affects scope, price, delivery, technical review, or approvals. Before authorizing work, make sure the parties are discussing the same version and that the responsible people have reviewed the relevant items.

Copyable outline

Use these headings to draft your own brief:

1. Project purpose: Intended use, success measure, location, and expected duration.
2. People and workflow: User count, tasks, hours, movement, access, and interactions.
3. Contents and equipment: Dimensions, quantities, weights if known, retrieval frequency, utility data, and special conditions.
4. Requirements: Must-have, preferred, optional, exclusions, and acceptable alternatives.
5. Site and delivery: Address, placement sketch, route photos, obstacles, ground, orientation, services, and movement plan.
6. Known approvals and reviews: Authority contacts, professional reviewers, status, and unanswered questions.
7. Responsibilities: Named owner for design, utilities, installation, inspection, maintenance, and handoff.
8. Open items: Question, responsible person, evidence needed, target decision date, and current status.

The document need not be elaborate. A clear, current two-page brief is more useful than a polished rendering based on untested assumptions. For a project discussion, send the essential facts and questions through the contact page, and confirm present capabilities and feasibility rather than inferring them from a sample image. Start with the customized solutions category, supplement it with the office-and-storage category where relevant, and use the service areas information to frame a location question. A disciplined brief does not predetermine the answer; it makes the next answer more relevant and helps the project decide early whether a custom approach is worth pursuing.