UB postcode district map, Ashford
Supplier statuses last checked .
The UB postcode area covers 12 districts and 7,216 live postcodes, from UB1 to UB18. It is centred on Ashford and also covers Gerrards Cross and Bushey.
Districts here average 601 postcodes.
Where the UB districts sit
Where UB sits
It falls across Greater London and Buckinghamshire.
Water supply across UB
All 12 UB districts are supplied by Affinity Water. That makes UB simple in a way many areas are not: one company, one set of rules, one status to check.
Affinity Water has a hosepipe ban in force from 11 July 2026, covering the whole of UB.
The shape of the UB area
UB3 is the largest district with 987 postcodes around Ashford, and UB11 the smallest with 19. The area divides into 40 postcode sectors.
The numbering is not continuous. UB runs up to 18 but has only 12 districts, so 6 numbers are unused:.
District by district: UB1 serves Ashford, UB2 serves Ashford, UB3 serves Ashford, UB4 serves Ashford, UB5 serves Bushey, UB6 serves Bushey, UB7 serves Ashford, UB8 serves Gerrards Cross, UB9 serves Gerrards Cross, UB10 serves Gerrards Cross, UB11 serves Ashford and UB18 serves Ashford.
Several districts share a settlement, which is a common source of confusion when a form rejects an address: UB1, UB2, UB3, UB4, UB7, UB11 and UB18 all point at Ashford, UB8, UB9 and UB10 all point at Gerrards Cross and UB5 and UB6 all point at Bushey.
What borders UB
UB sits next to HA (Bushey) to the north east, TW (Sunbury-on-Thames) to the south, W (London) to the east, WD (Rickmansworth) to the north and NW (London) to the east.
Its neighbours run in 4 different directions, so UB is landlocked by other postcode areas on most sides.
UB districts, settlements and water supply
| District | Principal settlement | Water company | Hosepipe ban status |
|---|---|---|---|
| UB1 | Ashford | Affinity Water / Thames Water | Ban in force |
| UB2 | Ashford | Affinity Water / Thames Water | Ban in force |
| UB3 | Ashford | Affinity Water / Thames Water | Ban in force |
| UB4 | Ashford | Affinity Water / Thames Water | Ban in force |
| UB5 | Bushey | Affinity Water / Thames Water | Ban in force |
| UB6 | Bushey | Affinity Water / Thames Water | Ban in force |
| UB7 | Ashford | Affinity Water / Thames Water | Ban in force |
| UB8 | Gerrards Cross | Affinity Water / Thames Water | Ban in force |
| UB9 | Gerrards Cross | Affinity Water / Thames Water | Ban in force |
| UB10 | Gerrards Cross | Affinity Water / Thames Water | Ban in force |
| UB11 | Ashford | Affinity Water / Thames Water | Ban in force |
| UB18 | Ashford | Affinity Water / Thames Water | Depends on your supplier |
Principal settlement is the town or city each district sits in or nearest to, derived from OS Open Names. It is not the Royal Mail post town, which is licensed data and not published openly. Status is resolved live from each company’s own notice.
Water hardness in UB
No water company covering UB publishes hardness figures as open data. The gap is named per district below so you know who to ask.
| District | Hardness | As published | Supply zone | Published by |
|---|---|---|---|---|
| UB1 | Not published by Affinity Water. Check with your supplier. | |||
| UB2 | Not published by Affinity Water. Check with your supplier. | |||
| UB3 | Not published by Affinity Water. Check with your supplier. | |||
| UB4 | Not published by Affinity Water. Check with your supplier. | |||
| UB5 | Not published by Affinity Water. Check with your supplier. | |||
| UB6 | Not published by Affinity Water. Check with your supplier. | |||
| UB7 | Not published by Affinity Water. Check with your supplier. | |||
| UB8 | Not published by Affinity Water. Check with your supplier. | |||
| UB9 | Not published by Affinity Water. Check with your supplier. | |||
| UB10 | Not published by Affinity Water. Check with your supplier. | |||
| UB11 | Not published by Affinity Water. Check with your supplier. | |||
| UB18 | Not published by Affinity Water. Check with your supplier. | |||
Hardness is published per census area, not per postcode, so these figures characterise a district rather than measuring one address. They are a scale and taste matter, not a safety one. Hardness data version wessex-water@2022-2025+yorkshire-water@2026.
Download the UB data
No signup, no email wall. GeoJSON carries the district points, the supplier and the live status, so it can be dropped straight into a map.
District positions are averaged postcode centroids from OS Code-Point Open. They show roughly where a district sits, not where its boundary runs, and are not legal boundaries.
Frequently asked questions
How many postcode districts are in the UB area?
There are 12 UB postcode districts, running from UB1 to UB18, and they contain 7,216 live postcodes across 40 sectors.
What towns does the UB postcode area cover?
UB covers Ashford, Gerrards Cross and Bushey. The area takes its name from Ashford, and each district is listed with its settlement in the table on this page.
Which water company supplies UB postcodes?
Affinity Water supplies all 12 UB districts. Supply boundaries follow the pipe network rather than postcode geography, so confirm against your water bill if you are near the edge of the area.
Why do UB1 and UB2 both say Ashford?
UB1, UB2, UB3, UB4, UB7, UB11 and UB18 all serve Ashford, covering different parts of it. A single town routinely needs more than one postcode district once it passes a few thousand delivery points, so this is normal rather than an error in an address.
Can I download a free UB postcode map?
Yes. This page offers the UB districts as GeoJSON, CSV and SVG, free and with no signup or email address required. The GeoJSON carries each district's position, its water company and its current restriction status, so it can be dropped straight into a mapping tool.
Which councils cover the UB postcode area?
UB reaches into Greater London and Buckinghamshire. A postcode area is not a council area: they were drawn for different purposes and a single district can sit across a council boundary, so your postcode does not tell you which authority you pay.
Why is there no UB17 postcode district?
UB17 is not in use. Postcode districts are allocated as sorting requirements change rather than numbered straight through, and a code that is retired or never brought into service is not reissued, so gaps in the sequence are normal.