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O&M manual vs building manual vs building log book: what's the difference?

The handover list has three lines on it. O&M manual. Building manual. Building log book.

You've got a fat O&M manual nearly done, so you tick the first one. Then someone asks whether the other two are "just the same thing with a different cover". And nobody in the site cabin is quite sure.

They're not the same thing. They overlap, they feed each other, and on most jobs you'll be asked for at least two of them. Here's how to tell them apart.

The short version

  • The O&M manual is the detailed reference. Every system, every product, every certificate. It's what the maintenance engineer opens when something needs fixing.
  • The building manual is the operator's guide to the whole building. Shorter, joined up, written for whoever runs the place day to day.
  • The building log book is how Approved Document L says to hand over the energy information regulation 40 requires, so the building can be run without wasting energy. It points to the other two rather than repeating them.

Think of it as zoom levels. The log book is the overview, the building manual is the operator's view, and the O&M manual is the close-up.

The O&M manual

This is the one you know. The operation and maintenance manual holds the detail for each installed system: system descriptions, datasheets, manufacturers' instructions, maintenance schedules, test and commissioning certificates, warranties and as-built drawings.

What goes in it, and when it's due, is usually set by your contract and the specification, so check those first. Our guide to what goes in an O&M manual covers the full contents list.

Who it's for: the maintenance team and anyone who has to service, repair or replace kit later.

The building manual

BSRIA's guide Building Manuals and Building User Guides (BG 26/2011) describes the building manual as an operator's guide to the building, capturing its design and how it needs to be run. It's a single document that can also record later changes to the building and yearly summaries of energy use and maintenance.

BSRIA recommends the delivery team compiles one, along with a shorter building user guide for the occupants. It isn't a legal requirement in its own right. You'll see it when the client or the spec asks for it, and on some BREEAM projects.

Who it's for: the facilities manager who needs to understand how the building works as a whole, not product by product.

The building log book

This is the one with a rule behind it, so it's worth getting right.

Regulation 40 of the Building Regulations 2010 applies where the energy efficiency requirement in Part L applies to the work. It says the person carrying out the work must, no later than five days after completion, give the owner enough information about the building, the fixed building services and their maintenance requirements for the building to be run using no more fuel and power than is reasonable.

For buildings other than dwellings, Approved Document L, Volume 2 explains how to do that. The 2021 edition, in section 9, says the operating and maintenance instructions should go to the owner in a building log book that follows CIBSE TM31. It says the log book should include:

  • information on the building, the fixed building services and on-site electricity generation, and their maintenance requirements, so the building can be run efficiently
  • a copy of the completed commissioning records
  • for new buildings, the data used in the energy calculations and the recommendations report from the on-construction energy performance certificate
  • for new buildings over 1,000m² of useful floor area, a forecast of actual energy use in kWh a year, broken down by fuel type
  • for work to existing buildings, details of what you actually did, such as new or upgraded thermal elements, windows and doors, and new energy meters

The approved document also says the log book may draw on or refer to the O&M manuals and the health and safety file. So you don't have to copy your whole manual into it. Point to it.

On a fit-out in a shell and core building, the log book should be updated for the first fit-out work too. That one catches people out.

Who it's for: the building owner, and whoever is trying to keep the energy bills sensible.

A change coming in 2027

A 2026 edition of Approved Document L, Volume 2 has been published. It takes effect on 24 March 2027 for most building work in England, and on 24 September 2027 for work on higher-risk buildings, with transitional arrangements set out in Circular Letter 01/2026. The log book guidance moves to section 8. It keeps the guidance on recording energy performance when you replace or alter systems in existing buildings (now paragraphs 8.7 to 8.10), with one change: work that 'alters' a system's energy performance, not only work that 'fundamentally alters' it, now means assessing the whole altered system.

The content list stays broadly the same, but the 2026 text no longer says the log book should follow CIBSE TM31. If your spec still names TM31, follow the spec. If it doesn't, check which edition applies to your job before you pick a template.

How they fit together on a real job

Picture a three-storey office refurbishment. New heating, new ventilation, new LED lighting.

  • The O&M manual has a section per system. The boiler datasheets, the AHU commissioning sheets, the emergency lighting certificate, the maintenance schedule.
  • The building log book is a short document. It says what systems are in the building, how they're meant to run, what the maintenance needs are in brief, and where the commissioning records sit. Each section points to the right part of the O&M manual.
  • The building manual, if the client asked for one, explains how the building works as a whole. How the heating and ventilation work together, what the occupied hours are, who to call for what.

Same facts, three levels of detail. Write the detail once in the O&M manual, then summarise and point to it from the other two. If a boiler changes during the job, you fix it in one place and the summaries still hold.

Three mistakes we see

  • Treating the log book as optional. Where Part L applies, regulation 40 needs that information handed over within five days of completion. The log book is how the approved document says to do it.
  • Copying the whole manual into the log book. It's meant to be a summary. A 400-page log book helps nobody. Summarise and point to the O&M manual.
  • Leaving the commissioning records out. The approved document lists them by name. If they're in the O&M manual, the log book should say where.

A quick check before you hand over

  • Does your contract or spec ask for a building manual or building user guide? If yes, it's a separate deliverable.
  • Does Part L apply to the work? If yes, the owner needs the regulation 40 information within five days of completion, usually as a building log book.
  • Which edition of Approved Document L applies to the job? That tells you whether TM31 is named.
  • Does the log book point to the right sections of the O&M manual?
  • Are the commissioning records in, and easy to find?

Where Handover Works fits

Handover Works builds the O&M manual from the job's documents, flags what's missing, and nothing is published until you approve it. Your client opens it in one scan. Get the detail right in one place and the other documents have something solid to point to. You can start free and pay when you publish.

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Related reading: What goes in an O&M manual?, How to write a system description for an O&M manual and Health and safety file vs O&M manual: what's the difference?

Sources

Handover Works team