Architectural drawings for Marylebone's terraces and mews

How each audit treats a roof extension

The audits agree on the principle, though each words it differently. Harley Street: Upward roof extensions would disrupt the unity of long terraces such as Mansfield Street and are unlikely to be acceptable. Portman Estate: Roof extensions are not always acceptable; Policy DES6C lists unimpaired terraces and complete compositions as unsuitable.

East Marylebone: Policy DES6 says roof extensions are unlikely where buildings are complete compositions or rooflines are exposed to long views. Dorset Square: On terraces with a consistent roofline, upward extensions would disrupt group unity and are unlikely to be acceptable. The pattern is consistent enough that we plan a mansard here only after we have found a justification in the existing roofline. The route is explained under mansard roof drawings.

Railings, ironwork and mews windows

Several audits treat boundary ironwork as part of the architecture. For the Harley Street area the audit says: The extensive original railings and ironwork are a key unifying part of the area's character. For Dorset Square: Railings enclosing the square's terraced housing are a prominent feature and key to its character.

Mews houses get a separate warning. Mews upper-floor windows lost to uPVC or different glazing patterns are noted as harm to mews character. Our elevations therefore record the original glazing pattern before any window is changed.

No Article 4 direction in two audits

The Harley Street audit and the Dorset Square audit each record that they carry no Article 4 directions. That does not leave a house free of control, because the conservation area itself still applies, and Westminster publishes 10 directions across the borough. We check the live register for your address.

Below ground and in the record

Westminster's City Plan 2019-2040 (2026), Policy 50, supports basements only where they extend under no more than 50% of the garden land and are no more than one storey beneath the lowest original floor level, with exceptions for large sites. The Marylebone Village Area of Special Archaeological Priority lies largely within the Harley Street Conservation Area around the north end of Marylebone High Street. Both points arrive early in a basement scheme, which is why our basement conversion drawings page puts the garden calculation first.

Westminster records 4,015 list entries, and our neighbouring guide to Mayfair's conservation area is the closest comparison for a listed Marylebone house.