Basements 

The new way to find space within your property is to extend down.  The Basement is now what the loft conversion was 20 years ago.  However, unlike a loft conversion a basement is a far larger structural undertaking and not for the faint hearted.  

The form the basement the existing building is underpinned with reinforced retaining walls.  These are cast in small sections to reduce the instability from above.  These retaining walls must be correctly designed and the conditions accounted for.  The London Clay is stable in the short term, but if a lens of sand is encountered this may flow into the excavation undermining large sections of walls.  Croft Structural Engineers has been called in on various occasions to take over when projects have gone a rye.

The practice has an extensive knowledge of basement design.  We have completed two storey basements and swimming pools under buildings.

Bendall Mews, Marylebone

A private developer required a basement to a new build property to ensure realisation of investment. The building was on a small site with multi-storey buildings either side.

Through commission an appropriate level soil investigation Croft was able to prove that the foundations to one of the buildings were sufficient and not additional work was required.  By removing the need to stabilisation a  saving of £12,000 was realised.  Stabilisation was required to the adjacent building and Croft provided a unique design to stabilise the high rise building.

Bolingbroke Grove, Clapham

Basement design requires the formation of new habitable areas under existing buildings, either by extending or deepening existing basements or, creating completely new spaces.

The knowledge that Croft has gained through a succession of basement developments means that we have the skills to implement work in this specialist field.  Close ties built up with various firms allow us to provide integrated solutions from initial consultancy to final fit out.

Opposite are photo of one such completed project.

Billing Rd, Chelsea

A new basement was completed under the existing house.  The house was also extended to the front rear and side at basement level, leaving only one wall line untouched.  During the works the entire early C18 property was temporary propped, new retaining walls cast and steel frames inserted.

The main structural design for this project was completed by a separate firm appointed by the building owner.  Croft Structural Engineers were called in by the contractor to provide specialist expertise to for the temporary works while the basement was constructed.

We work in close relation with the lead engineers and the contractor to ensure a safe temporary works solution was provided. 

The contractor appointed Croft Structural Engineers due to our large knowledge of basement works.

Fitzwilliam, Clapham

A new full length basement was requested and designed.  We worked closely with the contractor on site during the works to ensure that when unforeseen complications arose they could be answered quickly.

Major alterations were also design to the main building.  The ground floor walls to the rear were removed and the upper floors supported off steel frames.  The sequencing of this was crucial with the basement works.

Addison Place, Kensington

A new basement was required under a tight site.  Numerous alterations and variations of retaining walls were required to account for the varied party wall conditions. 

the property was unusual as it was a steel framed building not masonry.  Detailed and technical plastic analysis was completed to the steel frame to ensure the lengthened columns were still stable.

Addison Ave, Kensington

A private client required a new basement to his home.  We provided details and design to allow for a new basement to be constructed under the whole foot print of the property.  

With the whole foot print utilized adjacent properties had to be considered to ensure they were not undermined.  A major proportion of the work entailed ensuring Party Wall Awards were in place and agreed upon.