Architectural & Decorative Features

Architectural and decorative features are the projecting and ornamental parts of a façade: cornices, string courses, parapet balustrades, pediments, window surrounds, columns and pilasters, finials, brackets and sculpture, in natural stone, terracotta and faience, cast stone, render on armatures, pressed metal and, more recently, glass-reinforced concrete and fibreglass. They are concentrated on buildings from the mid nineteenth century to about 1940, and on later buildings in the classical or art deco manner.

Two facts decide how they fail. First, most ornament is held in place by hidden metal: iron or steel cramps, dowels and armatures, or anchors tying hollow terracotta units back to a steel frame. Second, projections shed water poorly unless their top surfaces were protected, typically with lead, copper or a weathered top, so water sits exactly where the hidden metal is.

What shortens life:

• Missing weatherings on cornices and string courses, so water sits on the top surface and runs into joints.
• Cement repairs and cement pointing, which trap moisture and force decay into the stone or terracotta beside them.
• Impermeable coatings painted over stone and render.
• Abrasive or acid cleaning, which removes the protective surface of stone and the glaze of terracotta.
• Vegetation and birds: roots in joints, guano holding moisture.
• Pollution, which forms sulfate crusts on limestone and marble.

Corrosion jacking of hidden metal

Iron cramps and dowels set in stone, and steel anchors holding terracotta, rust when water reaches them. The rust expands and splits the unit along the line of the fixing, often shearing off a corner or the front of a moulding. The fixing that was holding the piece in place is now what releases it. Cracks that follow the line of a hidden cramp, often with rust staining, are the signature.

Terracotta failure

Terracotta units are hollow, fired clay with a glaze or slip on the face. Crazed or cracked glaze lets water into the body; the water freezes or carries salts, and the glaze and face spall off. Water inside the unit reaches the steel anchors and, often, the steel frame behind. Units were frequently filled with brick or mortar, which holds water.

Stone decay

Sandstone scales in sheets parallel to the surface (contour scaling) from salt crystallisation, and stone laid with its bedding planes parallel to the face (face-bedded) delaminates. Limestone and marble form black gypsum crusts in polluted air that blister and fall away taking the surface with them. Soft stone erodes, losing the detail of mouldings.

Render ornament delamination

Render mouldings run on site or cast over brick cores and metal armatures lose their bond to the backing as water gets behind them. They sound hollow, crack around their perimeter, and can fall as a large piece.

Cornice and projection failure

A cornice is a cantilever of stone or terracotta held in place by its own back weight and by cramps, sometimes by the parapet above. Water on the unprotected top surface penetrates the joints, corrodes the cramps and decays the backing. Removing or lowering a parapet above, often done in past alterations, reduces the weight holding the cornice in.

Failed previous repairs

Cement patches and plastic repairs debond and fall; steel pins used in earlier repairs corrode in turn; resin repairs discolour.

From the street and from aerial imagery

• Missing pieces of moulding; fresh breaks lighter in colour than the weathered surface.
• Cracks along the line of mouldings and at the ends of units; rust staining from joints and cracks.
• Crazed, spalled or missing glaze on terracotta; replaced units in a different colour.
• Vegetation growing from cornices and parapets; birds nesting in projections.
• Netting over ornament, scaffolding sheds or hoardings at street level.
• Aerial imagery of the top surfaces of cornices and parapets: weatherings missing, vegetation, ponding.

Close up on site

• Hollow sound when tapped; movement of units under hand pressure.
• Sheet-like scaling and blistering of stone surfaces; black crusts.
• Open joints on top surfaces; failed or missing lead and copper.
• Previous cement patches debonding; corroded pins exposed.

In the records

• Façade inspection reports and ordinance filings with unsafe findings, and make-safe records.
• Records of fragments falling, and insurance or council correspondence about them.
• Conservation management plans and heritage consents for previous repairs.

Findings are graded by what they demand: safety (can hurt someone now), failure (failed and damaging the building), condition (distress present and progressing), lifecycle (renewal due on age and exposure), deadline (a regulator or ordinance sets the date), check (investigate before sizing works) and nil (cosmetic or stable).

A façade engineer or building surveyor with conservation experience leads, with a conservator or stonemason. Where the building is listed or heritage-registered, a conservation architect advises on method and consents.

• Close-up hammer survey of every unit over public areas and a sample elsewhere, removing anything loose at the time and recording it unit by unit on elevation drawings.
• Metal detection and ground-penetrating radar to locate cramps, dowels and anchors; borescope through joints.
• Opening up at representative locations to see anchor condition and the frame behind terracotta.
• Material analysis: stone identification, petrographic examination, mortar analysis, salt analysis.
• Infrared thermography to locate delamination in terracotta and render.
• Review of past repairs and their materials.

The report should map defects unit by unit, distinguish make-safe items from repairs, and specify methods and materials appropriate to the fabric.

• Make safe: remove loose pieces and store them for reinstatement; netting or sidewalk sheds until repaired.
• Re-anchoring: remove corroded cramps and replace with stainless steel; drilled stainless pins set in resin or grout through units into sound backing.
• Weatherings: lead or copper flashings over cornices and string courses; repointing of top joints with lime mortar.
• Stone repair: indents (new stone pieced in), lime mortar repairs for small losses, replacement units cut to profile.
• Terracotta repair: crack repair and glaze consolidation for minor damage; replacement units from a specialist manufacturer, or GRC or cast stone substitutes where approved.
• Removal of harmful earlier repairs: cement patches, impermeable coatings, corroded steel pins.
• Cleaning by low-pressure water, poultices or other methods suited to the material, not abrasive blasting.

Survey is a lump sum plus access. Repairs are priced per unit, per anchor, per linear metre of cornice or string course, or by area for repointing and cleaning. Access, often by scaffold over a footpath, dominates. Protective netting and sidewalk sheds are recurring costs until the work is done. Replacement terracotta has long lead times.

Two-part lines are normal. Make-safe and ordinance repairs are code compliance or repairs and maintenance; re-anchoring and weatherings are lifecycle; conservation repairs follow the heritage approval process.

• Australia. State heritage legislation (for example the Heritage Act 2017 in Victoria and the Heritage Act 1977 in New South Wales) and local planning heritage overlays control works to listed fabric; the Burra Charter of Australia ICOMOS sets conservation practice. There is no periodic façade inspection regime; the owner's duty to the public is general.
• United Kingdom. Works to listed buildings need listed building consent under the Planning (Listed Buildings and Conservation Areas) Act 1990; BS 7913 guides the conservation of historic buildings and BS 8221-1 and BS 8221-2 cover cleaning and repair; Historic England publishes technical guidance on stone, terracotta and lime.
• United States. The Secretary of the Interior's Standards for the Treatment of Historic Properties and the National Park Service Preservation Briefs (Brief 7 covers glazed architectural terra-cotta) set practice; local landmarks commissions control listed buildings. New York's FISP examines ornament on buildings over six storeys every five years, and its parapet rule requires annual observation of street-facing parapets; Chicago, Boston and San Francisco have similar regimes.

• Façade inspection reports, ordinance filings and make-safe records.
• Records of falling fragments and any incident reports.
• Heritage listing, conservation management plan and consents for past works.
• Specifications and records of previous repairs, with materials used.
• Netting, shed or hoarding records and their duration.

• Records of cleaning methods used on the façade.