Mind your wall claddings

By - , Build 172

Proper on-site management of the wall cladding is critical to delivering quality buildings. In the third article in this series, we look at the storage requirements for many different types of wall claddings.

Weatherboards protected under secure covers.
Store bricks shrink-wrapped on pallets clear of adjacent buildings.
Prefinished weatherboards protected in covered storage (note that the ends are not yet sealed).

WALL CLADDINGS are what we see when we approach a building, and any defects from poor handling, storage or installation may be visible. They can also affect the durability of the cladding.

Challenges with storage and handling

Looking after wall claddings during delivery, storage and installation means:

  • planning for deliveries
  • providing access for delivery vehicles
  • designating an appropriate storage area where cladding can be stored:
    • protected for wall claddings that need to be kept dry before installation
    • on their delivery pallets outside for bricks and concrete blocks
  • planning for handling, such as lifting and carrying for upper-floor claddings
  • employing the correct manual handling techniques to distribute materials around the site to their installed location.

Additional challenges when storing and handling cladding materials include:

  • accommodating long lengths – for example up to 8 m long uPVC weatherboards or 12 m long profiled metal and flashings
  • carrying long and relatively floppy sheet materials – additional labour may be required
  • wind loads on sheet materials stored outside
  • weight and bulk for bricks and concrete blocks
  • prefinished materials.

Bricks, concrete blocks and stone

Leave these shrink-wrapped on the pallet until required. Pallets should be lifted onto a flat surface clear of buildings and fences to allow adequate air circulation and give easy access for handling.

They should be hoisted or transported using a pallet jack. Avoid carrying bricks and blocks in a wheelbarrow unless absolutely required.

Store bricks shrink-wrapped on pallets clear of adjacent buildings.

Fibre-cement sheets and weatherboard

Fibre-cement sheets, weatherboards, planks and trims must be stored laid flat on a smooth level surface and edges protected from chipping.

Sheets and weatherboards should be carried in the vertical position, not flat, to avoid excessive bending.

To ensure optimum performance, store under cover and keep dry prior to fixing. If they become wet, allow to dry thoroughly before fixing. Sheets stored outside are susceptible to wind damage unless securely tied down.

Sheets and weatherboards that will be painted but are supplied without a primer or sealer coat should be coated immediately to seal and minimise the risk of unacceptable water absorption before the product is installed.

Primer applied to weatherboards or sheets should not be exposed to the weather for more than 30–45 days, depending on the primer. Ideally, the next coat of paint should be applied as quickly as practicable.

Timber weatherboards

Timber weatherboards must be stored laid flat on a smooth level dry surface, clear of concrete slab or timber floors. Store on slats to allow air movement and under cover. Keep dry prior to fixing. If they become wet, allow to dry thoroughly before fixing.

Timber weatherboards supplied without a primer or sealer coat that will be painted should be coated immediately in dry conditions to seal and minimise the risk of unacceptable water absorption before the product is installed.

Primers used to factory preprime timber in New Zealand are typically thin holding primers designed to provide temporary protection during the building process. The timber must be sanded and primed with a primer.

Timber weatherboards should only be painted when dry and the board is near equilibrium moisture content (MC<16%). H3.1 treated weatherboards and trim require all surfaces to be painted before installation including all holes and notches.

Similar handling and storage practices to those above for timber weatherboards can be applied to:

  • timber boards and battens
  • plywood weatherboards
  • reconstituted wood weatherboards.
Weatherboards protected under secure covers.

uPVC weatherboards

uPVC weatherboards are delivered plastic wrapped and must be:

  • stored in dry undercover conditions if they are not going to be installed within a few days
  • stacked flat, clear of the ground with no other materials on top of the planks
  • supported on bearers at 600 mm maximum centres
  • restrained from collapse
  • carried on edge, taking care to avoid damage to the plank edges, ends and the weather surface.
Prefinished weatherboards protected in covered storage (note that the ends are not yet sealed).

Plywood

Flat sheet plywood cladding and rigid air barriers may be treated or untreated.

Untreated plywood is generally dispatched with a moisture content of 8–15%. It will respond to changes in ambient humidity so the eventual moisture content will depend on the environmental conditions. The veneers swell or shrink across the grain in response.

CCA-treated plywood is dried following treatment to an average moisture content of approximately 18%.

Storage and handling

Carry sheets on edge and locate storage so that sheets will not be exposed to mechanical damage.

When storing plywood, keep dry and protected from sun, rain and wind that can bring rapid changes in temperature and humidity and cause staining, fading and surface checking. Keep the stack clear of the ground in a well ventilated area. The H3.1 LOSP solvent smell can be quite strong, and venting is recommended until most of the solvent has evaporated.

Stack sheets flat. Support the sheets at both ends and the middle to avoid distortion – align bearers in packs over bearers in packs below. Do not store other materials on the plywood or use it as a platform or table. Secure sheets stored outside against wind uplift.

Fillets used to separate sheets in drying may leave marks on the sheet surface, but these will fade. They can be disguised with paint but may be visible under stain.

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Once installed

Ensure plywood cladding is below 18% moisture content before installing moisture-sensitive materials, coverings, coatings or adhesives.

Untreated plywood will withstand rain wetting and exposure during construction for up to 3 months. In high temperatures and high rainfall, this period may be less. Discolouration and face checking of the sheet surface can be expected when exposed for longer periods.

Where the moisture content exceeds 18% for prolonged periods, plywood must be H3.1 LOSP or H3.2 CCA-treated to resist decay or insects.

When coating H3.1 LOSP-treated plywood, there may be traces of residual solvent on the sheet surface from the treatment process. Sheets that are greasy to touch should be placed in a well ventilated area and allowed to flash off to ensure proper adhesion of paints and stains to the sheet surface.

Prefinished profiled or plank metal claddings

There is risk of damage to the prefinished surface and denting of the materials. Once installed, they must be protected from cement splashes that can mar the surface.

Store under a water-resistant cover, clear of the ground to provide airflow around the bundle. If the material has become wet during transportation or in storage, wipe it down to remove moisture and then fillet or cross stack it to ensure air circulation between the sheets. If sheeting has been wet in storage for over 3 days, it should not be used because of the permanent surface staining that may have occurred.

When handling and storing:

  • evenly position the materials on untreated evenly spaced dunnage to prevent deformation – packs should be no greater than 1000 mm high and on a slight incline to allow water run-off
  • store the material in the order it will be installed
  • peel and lift the sheets off the bundle – do not slide or drag sheets or planks across each other or over rough surfaces
  • sheets or planks longer than 3 m should be handled by two people and carried on edge to avoid buckling
  • keep material clear of any substances that may cause damage
  • tie down stored material and accessories as they are susceptible to wind damage
  • strippable protective film must not be exposed to sunlight or UV during storage – remove the film immediately after installation.

Zinc claddings

Transport and store zinc claddings under dry ventilated conditions so white rust does not form. Avoid any contact between wet sheeting or tarpaulins and the surface of the metal during storage.

For good transportation and storage of zinc, ensure:

  • there is good air movement around stored materials
  • it is stored on dry covered pallets on a dry floor
  • it is tightly stacked to prevent chafing
  • sheets are protected from abrasion
  • material is allowed to sit unopened for several days to allow for acclimation to the storage area’s temperature and humidity
  • acidic perspiration and fingerprints are immediately removed – wear clean gloves when handling material during transportation, fabrication and installation
  • all strippable film (PVC) is removed as soon as possible after installation – partial removal may give an uneven patina, and avoid shop-applied protective films as these may trap air and moisture leading to formation of zinc hydroxide stains.

Glass as a cladding

Glass used as a curtain wall cladding material is arguably the most fragile material covered here and, when used with some other claddings, the most susceptible to damage. Handling and storage requirements for glass include:

  • leaving the glass within any protective crating until immediately before use
  • storing individual sheets of glass on edge supported by dunnage with an isolating layer between sheets
  • storing and handling clear of metal and other brittle materials and operations such as placing concrete
  • keeping the glass dry
  • using the correct lifting apparatus to prevent edge or surface damage
  • securing the glass back to a rigid structure to prevent overturning.

Metal-faced panels

Metal-faced panels with aluminium, steel or magnesium oxide board come in various options, including thin-stressed prefinished aluminium or steel skin panels with a polystyrene or polyurethane foam core in several thicknesses.

While more commonly used on commercial buildings, both panel types are utilised as wall cladding systems on residential buildings.

Ideally, panels should be delivered and lifted into their final position. If they need to be stored:

  • stack clear of the ground on evenly spaced bearers
  • leave the protective film in place until panels are installed
  • fully cover to keep them dry.

Exterior insulation and finish systems

Specific material storage and handling requirements for exterior insulation and finish systems (EIFS) – polystyrene overcoated with acrylic or polymer modified cement plaster – include:

  • storing polystyrene sheets under cover on a level platform protected from UV
  • providing a dry storage area for the powdered components of the plaster
  • minimising exposure of the polystyrene to UV once erected – any yellowing of the surface from UV must be removed before plastering commences.

Precast concrete

Precast concrete component deliveries should be planned so that the panels can be lifted directly into position and braced. Where panels must be stored, they must be placed on strong and level supports positioned so the precast components are not subject to excessive stress.

Recommended quality control checks include:

  • structural defects – cracks
  • dimensional tolerances are within the limits specified
  • surface finish quality is as specified
  • physical damage – chipping or staining
  • shrinkage cracking.

Lightweight aerated concrete

Lightweight aerated concrete is supplied as panels or blocks that are then plastered. Storage requirements include:

  • providing dry storage for panels and blocks and components of the plaster system
  • avoiding sagging or damage to ends, edges and surfaces
  • storing uPVC accessories flat and protected from direct sunlight
  • a maximum stack height of two panel bundles
  • stacking panels on edge on dunnage.

When handling lightweight aerated concrete:

  • utilise supplier-developed handling systems such as hoists, lifters and trolleys – some suppliers require the use of approved lifting devices for unloading and moving materials
  • keep manual handling to a minimum for larger items
  • ensure appropriate bracing is installed to packs prior to removal of strapping to prevent panels from falling
  • packs should be unloaded and stored as close as possible to the intended installation area.

Cladding system components and accessories

Some cladding systems require the application of plasters or use of mortars to complete the installation. Store dry components such as:

  • cement and finishing plasters in a dry, protected area
  • sand covered to protect from contamination such as dirt and cat faeces
  • fibreglass mesh protected from sunlight
  • flexible wall underlays under cover to protect from damage, water and UV
  • bright steel nails in dry conditions.

Liquid or flexible components must be stored in frost-free conditions. There are also recommended temperatures that should not be exceeded. Silicone rubber stored at 27°C, for example, will have a shelf life of about 6 months. Material stored at 38°C will have a shelf life of about 2 months.

It is also important to rotate stored stock such as cement, primer, sealants and adhesives to ensure material is within it use-by date.

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Articles are correct at the time of publication but may have since become outdated.

Weatherboards protected under secure covers.
Store bricks shrink-wrapped on pallets clear of adjacent buildings.
Prefinished weatherboards protected in covered storage (note that the ends are not yet sealed).

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