UK SIC 2007 · 71129
Other engineering activities (SIC code 71129)
Other engineering activities is UK SIC code 71129. It sits in division 71 (Architectural and engineering activities; technical testing and analysis) of the SIC 2007 list. On the August 2026 Companies House register, 37,759 active UK companies list 71129 among their SIC codes. 26,674 of them list it first. That makes it the most used code in its division.
Architects, engineers and technical testing labs share this division. Engineering leads on numbers. Code 71129 holds general engineering activities. Code 71122 covers scientific and technical consulting. Code 71121 covers design work for industrial process and production. Architecture splits in two: 71111 for architectural practices and 71112 for urban planning and landscape work. Code 71200 marks testing and analysis houses, from materials labs to environmental testing. Many entries are chartered professionals in small limited companies. Established multidisciplinary firms sit alongside them.
Related SIC codes
Who prospects SIC 71129 companies
Construction supply chains drive most of the selling here. Main contractors and developers search these codes to find design partners. Software vendors sell CAD, BIM and project tools. Insurers push professional indemnity, which every practice has to carry. Recruiters work the engineering codes hard, because demand for chartered engineers beats supply. A new incorporation often means a senior engineer or architect has left a big practice with clients in tow. Steady filings plus visible growth mark the firms winning places on frameworks.
Lead generation for trades & construction →How to read SIC 71129
SIC 71129 is a five-digit code, and the digits are not arbitrary. The first two, 71, are the division, architectural and engineering activities; technical testing and analysis. Add the third and you have group 711; the fourth narrows it to a class, and the fifth to the subclass, which is the level Companies House actually asks a company to pick. The whole division sits under section M, professional, scientific and technical activities, the broadest tier there is. Reading a code left to right therefore goes from a whole sector down to one activity.
More on how SIC 71129 is built
A company chooses its own codes when it incorporates and can change them on any confirmation statement. It may list up to four, and Companies House does not check whether they are right. That is why 71129 is worth reading as a claim the company made about itself rather than as a verified fact, and why the first-position and any-position counts above differ.
Measured on the August 2026 register, the busiest registered-office post towns for 71129 are London (5,109), Warrington (584), Glasgow (564), Aberdeen (535) and Manchester (475). Those are registered-office locations, which is where the paperwork sits rather than necessarily where the work happens, so treat them as where to start looking rather than as a service area.
Using SIC 71129 as a filter
37,759 companies is 0.73 per cent of the 5,190,464 active companies on the UK register, and ranks 71129 most used of the 6 codes we track in division 71. That is the pool before any filter. Whether it is a big market for you depends on what you sell, but it is the number every other filter on this page cuts down from.
More on filtering by SIC 71129
26,674 companies put 71129 first and a further 11,085, 29 per cent, list it in one of their other three SIC slots. That gap is the difference between a tight list and a broad one. First-code-only is the safer filter when you are writing to them; matching any position is worth it when you need the volume.
These companies are spread out. London is the largest single cluster at 14 per cent and the top five post towns together hold only 19 per cent, so the remaining 81 per cent sits across the rest of the country. A regional filter narrows this list without gutting it, which makes it a reasonable code to work territory by territory.
In practice the code on its own is rarely the whole filter. Pair 71129 with an incorporation date to catch companies in their first months, when they are still choosing suppliers, or with a filing deadline to reach them while the year end is on their mind. A worked example for this code: 71129, registered office in London, incorporated in the last ninety days, which turns a 37,759 company pool into a list you can write to in an afternoon. Add the poor-website filter if what you sell is a website, or a recent change of officer if you sell to whoever just took the job. Every company you pull carries the Companies House record, the director's name, a verified website and a verified email, and the ones we cannot complete are not charged.
Where SIC 71129 clusters in the UK
ACTIVE COMPANIES BY REGISTERED-OFFICE POST TOWN · COMPANIES HOUSE REGISTER, AUGUST 2026
SIC 71129 companies, as leads
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About SIC 71129
How many UK companies use SIC code 71129?
37,759 active UK companies list 71129 (Other engineering activities) among their registered SIC codes. Each company may register up to four. Of those, 26,674 put it first. The figures come from the August 2026 Companies House register snapshot, and count active companies only.
Should an architect use SIC code 71111 or a construction code?
A design practice belongs under 71111, or 71112 for planning and landscape work. Division 41 and 43 codes describe businesses that physically build. Companies House does not police the choice. One thing does matter: the title architect is legally protected in the UK by the Architects Registration Board. Only ARB-registered individuals may use it, whatever SIC code the company holds.
Which SIC code fits a consulting engineer?
Most consulting engineers pick 71122 for scientific and technical consulting. Code 71121 suits industrial and production design. The broader 71129 works when neither is a clean fit. The choice is yours. Codes are self-declared at incorporation and amendable on any confirmation statement (CS01). A company can carry up to 4, so many practices pair an engineering code with a project management or testing code.
Find UK SIC 71129 companies
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