Enderby House, Greenwich

By Tom Haynes

Structural Renovations Enderby House

The site was first developed in the 1830s by the firm Samuel Enderby & Sons, who were the largest commercial whaling and sealing company in Britain. The Company was so famous at the time that Hermann Melville immortalised the Enderby family in his book ‘Moby Dick’.

Enderby House was built in 1846, as both a home and office premises for the Company, until the decline in whaling led the Enderby’s to cease their enterprise in 1854.

Glass Elliott & Co. took over the site to manufacture and lay transatlantic telegraph cables. It is interesting to note that the SS Great Eastern was used as a cable laying ship due to its sheer size being capable of holding the required amount of cabling. Numerous takeovers and mergers took place over the years and the last cables were manufactured on the site in 1975. The communications company Alcatel, who purchased the site in 1994, eventually sold a large part of the site, including Enderby House, to Barrett Developments for housing, which commenced in 2014.

Enderby House was Grade II Listed in 1973, due to it close links with local industry and technology development.

Our works were concerned with extensive masonry stabilisation, as decades of neglect had taken their toll on the 170-year-old structure. A comprehensive scheme was developed between Helifix and ourselves, which saw 6mm diameter Helifix HeliBars being installed to form load-bearing masonry beams and to stabilise cracked brickwork. This was followed by the installation of Helifix 8mm diameter CemTies to pin the window head/arches to the newly formed beams.

The project was completed within a challenging contract programme, where numerous other trades were present.

Enderby House will now re-open as a public house run by Young & Co. Brewery PLC.

Westlands Primary School, Sittingbourne

By Tom Haynes

Structural Renovations Helifix

Structural Renovations secured the works to complete concrete repair and masonry stabilisation to Westlands Primary School in Kent, working as a specialist sub-contractor to Kier Construction.

Westlands Primary School was constructed in the 1960’s and is a typical example of many schools built during the period with brick facades, reinforced concrete features such as window cills, window surrounds, columns and flat roofs with overhangs.

The window cills, lintels and surrounds are constructed from reconstituted stone or ‘engineered stone,’ using natural stone aggregates, such as portland, mixed with a cementitious binder, that is intended to resemble natural quarried stone. A recurring issue with this type of construction is that the embedded mild steel reinforcement which is used to provide tensile strength is compromised by both low cover and the relative high porosity of the reconstituted stone. This leads to expansive corrosion of the reinforcement (due to the presence of moisture and oxygen) and causes the ‘stone’ to crack and spall. Entire sections can be damaged by this process and repair is generally the most cost effective and practical method of treatment.

The treatment in this instance was to mechanically remove all loose and defective ‘stone’ together with any reinforcement that had lost significant section. New stainless steel reinforcement was fixed in position using a two part polyester resin. A temporary timber shuttter was formed to the profile of the area to be reinstated, which included drip, upstands and falls. The prepared broken back surface and reinforcement was coated with Sika MonoTop 610 and reinstated with Sika MonoTop 615 back to the original surface profile.

The brickwork in places at Westlands Primary School had diagonal, stepped cracking which required stabilisation. These were reinforced using Helifix Helibars set in Helifix Helibond Grout, a non-shrink cementitious grout, within the bed joints at regular centres along the length of the crack. Once installed the reinforced areas were repointed to match the existing pointing.

The works are to be completed over a number of phases to suit both the major refurbishment scheme by the Principal Contractor as well as the school term times and operating hours.

Royal Hospital Chelsea

By Tom Haynes

Royal Hospital Chelsea

Grade I listed and designed by Sir Christopher Wren, ‘The Royal Hospital’ was founded by King Charles II in 1682 as a retirement and nursing home for soldiers of the British Army.

The hospital is situated close to the River Thames, in the the Royal Borough of Kensington and Chelsea on a 66 acre site. The residents of the hospital are known as ‘Chelsea Pensioners.’

Structural Renovations were employed by Wates Construction to stabilise the chimney breasts within the building, reform feature brickwork dressings around windows and repairs to stonework within a number of the rooms.

The chimney breasts had the timber panelling removed exposing the cracked brickwork beneath. Bed joints at regular centres were ground out, being careful not to damage the 300 year old hand-made bricks. Stainless steel helical bars, set in non-shrink cementitious grout were installed into the pre-soaked slots. The slots were then repointed using a lime mortar.

The deep red brickwork dressings around some window openings had, over time cracked and spalled due to expansive corrosion of metal inclusions and frost damage following moisture ingress. The defective brickwork was removed using only hand tools to avoid further damage.

Stainless steel pins were drilled in to sound substrate and set in a two part polyester. Usually a specially colour matched, modified mortar, the repaired areas were reinstated and whilst still not fully cured the brickwork was carved to the required profiles to include ‘dummy’ perp and bed joints, which were subsequently pointed with another colour-matched mortar.

Stone work repairs were completed using stainless steel pins for support and a colour-matched, modified mortar.

This project was secured with Wates following successful completion of masonry repairs to Somerset House another one of London’s Grade I listed buildings.

Broadbent Building, Heron Hall Academy

By Tom Haynes

Heron Hall Academy

The Broadbent Building and adjacent gym block on the site of the former Middlesex University campus in Enfield, has undergone a major refurbishment as part of the new Heron Hall Academy project.

The art-deco facade is of a special interest and incorporates, now listed ceramic tiles. The building is constructed from brick with reinforced concrete floor slabs supported by reinforced concrete columns and beams.

Working as a specialist sub-contractor to Willmott Dixon Construction, following successful completion of other recent projects, we have been repairing and coating the external concrete elements which include the window cills, window heads and roof overhang, which project around the full perimeter of the buildings on all facades, as well as the entrance canopies.

The works have been carried out using Flexcrete materials and have included; Monolote hand-placed repair mortar for the repairs the the defective concrete and Monolevel 250F as a fairing coat, which has been specially formulated for application over existing coatings, being applied to all exposed concrete surfaces. To complete the system two coats of Monodex Smooth, a protective anti-carbonation coating primed with Bond-Prime, was applied. The system provided the client with 15 year guarantee.

Whilst on site we were also instructed to carry out internal concrete repairs using Flexcrete Monomix repair mortar, external brick stitching using Helifix Helibars and the installation of new expansion joints.

We are due to return to site in the new year to compete the second phase of the works.

Safestore, Edgware

By NTD

Safestore

The Safestore building in Edgware is a large industrial unit comprising a reinforced concrete frame (columns and floor slabs/beams) and brickwork infill panels.

An investigation was carried out by Martech Technical Services to establish the causes and the extent of defective concrete. During this investigation it was identified that the brickwork panels were moving under light hand pressure. After further investigation it came to light that there were no ties between the outer leaf of brickwork and the inner leaf of blockwork in any of the panels.

We were awarded the contract to installed Helifix DryFix remedial wall ties to tie the inner and outer leaves of brickwork together as well as the outer leaf of brickwork to the concrete columns. Specially designed steel wind posts were fabricated and installed at the midpoint of the brickwork panels by our sub-contractor, Artistic Engineering Limited. These were deemed necessary due to the brickwork panels being the largest size that building regulations permit.

In addition to the above issues, the building’s concrete frame was also in a poor state of repair. Following the full site investigation, extensive concrete repairs were undertaken. Furthermore, the concrete frame was provided with corrosion control by the installation of Margel Vapour Phase Inhibitor pellets, a migrating corrosion inhibitor in capsule form, followed by the application of a pigmented anti-carbonation coating. 

Additional works were carried out which included the waterproofing of an external staircase using one of Sika Limited’s flooring products and the removal of 2 no. large window sets and replacement with rendered blockwork.

The building remained occupied throughout with the site foreman working closely with Safestore staff and customers as well as the users of adjoining properties.

Safestore, Battersea

By NTD

The Safestore self storage facility is located in Battersea in south London and was originally constructed as a depository in 1901.

Following the successful completion of external repairs to two other Safestore sites in Islington and Edgware, we were awarded the 21 week contract for the repairs and refurbishment of the front, rear, flank ends and internal structural elements together with waterproofing to the roof.

Due to the close proximity of the railway line at the rear of the building and the requirement to keep the building in operation with as short a programme as possible, a combination of scaffold fans, temporary suspended electric cradles and abseil techniques were used to access the facades.

The faces of damaged brickwork were repaired using Remmers colour matched Restoration Mortar and where severely damaged, individual matching bricks were replaced.  Cracks were repaired by resin injection and installation of Helifix HeliBar, helical bar reinforcement, followed by extensive brickwork repointing.

New movement joints were created in external solid walls by cutting vertically and then installing horizontal sleeved HeliBars across the newly formed joints.  The joints were then completed by sealing with a polysulphide mastic.

The reinstatement of the details to the damaged dressed stonework was also carried out by ‘dubbing’ with a polymer-modified, structural repair mortar and completed using the appropriate Remmers colour matched mortar. Rendered bands were decorated using external grade masonry paint.

Concrete repairs were carried out within the penthouse structure using Fosroc Renderoc, pre-bagged, lightweight repair mortar, where soffits had failed due to the expansive corrosion of the buried filler joists, caused by long-term water ingress through the failed roof covering above.

To prevent further water penetration from the roof, Sika LPL’s Decothane System, a glass fibre reinforced liquid roof membrane, was applied to the roof areas. Once completed a Single Point Guarantee, provided by the manufacturer, was issued to the client providing assurances they required for the building’s continued serviceability.

Whilst the above works were being carried out the client also took advantage of having the steel framed windows refurbished and fully redecorated and any broken glass replaced.