Dixon St Flats Asphalt Tune-up

The Dixon Street Flats in central Wellington were completed in 1944 as part of the first Labour Government’s state housing programme. The building was the first major high-rise building and first major apartment block to be completed in Wellington after the Second World War. Ten stories high, it contains 115 one-bedroom flats plus a two-bedroom caretaker’s flat.
View of the newly completed Dixon Street Flats in Wellington, taken by John Dobree Pascoe, circa 1943 View of the Dixon Street Flats from Willis Street circa 1943. Alexander Turnbull Library
Access to the apartments (flats) is from the rear, via 9 levels of balconies/walkways/external corridors. Access to the walkways is by two sets of stairs at each end and two sets of lifts in the center.
The walkways were originally waterproofed using 1″ (25mm) thick trafficable Mastic Asphalt.
In the 1970’s during refurbishment the original mastic asphalt was overlaid with new 1/2″ (12mm) roofing grade mastic asphalt.
By 2009/10 the exterior of the building was in need of serious repair, including the walkway mastic asphalt.
The work had to be carried out while the building was still occupied, so the option of totally removing the two layers of mastic asphalt and replacing with new was not viable. As the building has a Historic Places Category 1 classification, the Housing Corporation and their Architects wished to retain the look of the mastic asphalt walkways as close as possible, yet bring them back to being waterproof and serviceable.
The solution we came up with was to repair the mastic asphalt using traditional mastic asphalt repair techniques and then apply a Nuralite Nuracolour coating system, with added silica sand to provide a non slip, tougher wearable and UV protective finish. The colour chosen was Ship Grey, to give the appearance as close as possible to how the the original mastic asphalt would have appeared after having aged a few years.

Introduction

The images below show the extent of the work (1200m2 over nine levels) and examples of some of the defects requiring repair.
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view of the rear balconies 2007 view of the rear balconies 2007 rear of the building scaffolded and screened 2008 typical walkway balcony, level 1 typical crazing Small lines) and two splits crazing on the flat and crack in the angle fillet split forming along bay joint low view along a typical balcony two splits at the top of the external stairs some splits, also clear difference in the bay areas another few splits a bubble, and an old repair top left a radiated impact crack a split near the external stairs an old repair, but it has split again twos shades show bay areas, split out of corner small alcove defect in plaster mortar has exploded a radiated impact crack an old repair, but it has split again bay joint is splitting apart more splitting, possibly old impact crack defect in plaster mortar has exploded (See 19 and put before) bubble/blister and split radial splitting along bay joint old repair has been impacted again, radial splitting cracks in skirting along internal wall bay joint is splitting apart another typical walkway/balcony pipe has been cut through skirting mastic asphalt a gobbed up with sealant, drill likely cracked the asphalt splitting at angle fillet bay joint is splitting apart doorway has had plywood step fitted over mastic asphalt more bay joints splitting apart external stairs slumping on risers external stairs slumping on risers top of the external stairs splitting at angle fillet splitting at angle fillet split at top of stairs external stairs slumping on risers

Mastic Asphalt repair Work

the asphalt blocks were melted in this LPG fired repair pot areas of splitting along bay joint, to be repaired the split is warmed then dug out with a hot trowel the hot mastic asphalt is applied as a poultice it is smoothed and levelled to the surrounding area some repairs along the angle fillet, internal wall stairs slumping, to be repaired hollow slumping is chipped out first coat of mastic is applied second coat is applied, flush with the surrounding area bubble/blister heated an d dug out with hot trowel poultice of hot mastic asphalt is applied finished repair flush with surrounding area poultice of hot mastci being applied to repair split in angle fillet finished repair to angle fillet more angle fillet repairs more step slumping to repair, bucket pot at top melting asphalt spreading the asphalt into the riser more step repairs later surrounding asphalt is ground with diamond grinder to remove crusty old surface and crazing more angle fillet repairs at high level more repairs to splitting long bay joint more angle fillet repairs severe bubbling/blistering in this area at top of stairs, repaired more angle fillet and bay joint repairs at lower level cracks in skirting along internal wall cracks are repaired with mastic asphalt more kirting crack repairs, and bubble/blister repaired on the flat later when the old surface is diamond ground the repairs are almost invisible grinding the old asphalt with diamond grinder to remove crusty old surface and crazing upstands have been skim ground to remove crazing and provice a key for the Asphalt Primer close up view of grinding off over repaired area next step after grinding is pressure washing to remove dust and debris
pressure washing example balcony after grinding and cleaning, dry ready for asphalt primer

Nuracolour UV protective and wearable Coating System

application of Asphalt Primer begins level 4 half of level 4 is primed with Asphalt Primer wall side and under parapet fence is primed with asphalt primer half of door entry is primed, signs directing foot traffic Asphalt Primer complete to level 4 ramp for tenants to access over newly primed asphalt in doorway entry Asphalt Primer complete to level 8 reverse view of previous image, level 8 another primed balcony another primed balcony Asphalt Primer complete to level 3 first coat of Nuracolour to skirtings and doorways, ramps for access at doorways level 5 skirtings and under parapets have first coat of Nuracolour level 4 skirtings and doorways have first coat of Nuracolour level 9 has first coat of Nuracolour to half area half width balcony level 2 is cordoned off to traffic for first coat of Nuracolour reverse view of previous image half width balcony is cordoned off to traffic for coating level 5 has first coat of Nuracolour level 3 has first coat of Nuracolour level 1 has first coat of Nuracolour  level 6 first coat of Nuracolour, painters have been working on the walls level 8 second coat to skirting side just been applied, foot traffic keep right level 8 second coat to parapet side just been applied, foot traffic keep right level 8 finished, coating is dry, cordon and ramps removed second coat completed level 9 another level completed another level completed level 7 completed level 2 completed second coat in doorway wear and tear on our brushes, newer at top
set of stairs ground smooth ready for coating same stairs with finished Nuaracolour system

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