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Steadmans’ AS Twin-Skin Steel Cladding Roof and Wall systems consist of coated steel sheets rolled to five different profiles; they may be used form roofs – down to 4 degrees pitch (6 degrees if rooflights are required) and walls. The system includes a comprehensive range of fixings, sealants, guttering, flashings and rooflights.

The AS Twin-Skin Steel Cladding systems offer rapid coverage and swift completion of a weatherproof building envelope to give a high performance building.

Applications

Twin-Skin Steel Cladding applications are used where an insulated system is required, often to improve the efficiency of the building. Steadmans twin skin system is used in a wide range of buildings and situations from warehousing and industrial applications to office and showrooms. Steadmans’ AS Twin-Skin Steel Cladding roof and wall systems consist of coated steel sheets rolled to six different profiles to suit the needs of wide range of applications. The system may be used to form roofs – down to 4° pitch (6° if roof lights are required) – and walls.

We offer a wide and comprehensive range of spacers, fixings, sealants, guttering, flashings and roof lights to suit the differing situations that this versatile system can be used within. Steadmans AS Twin-Skin Steel Cladding system offers rapid efficient coverage and swift completion of a weatherproof building envelope to give a high performance building.

Specifications

AS Twin-Skin Steel Cladding roof and wall profiles are manufactured in a process certified to ISO 9001:2008.

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References

  • Approved Documents
    • A Structure
    • B Fire safety
    • C Site preparation and resistance to contaminants and moisture.
    • L2A Conservation of fuel and power in new buildings other than dwellings.
    • L2B Conservation of fuel and power in existing buildings other than dwellings.
  • The Scottish Building Standards: Technical Handbook.
    • Non-domestic.
  • BS 476 Fire tests on building material and structures.
    • BS 476-3:2004 Classification and method of test for external fire exposure to roofs.
    • BS 476-7:1997 Method of test to determine the classification of the surface spread of flame of products.
    • BS 476-22:1987 Methods for determination of the fire resistance of non-loadbearing elements of construction.
  • BS 5250:2002 Code of practice for control of condensation inbuildings.
  • BS 5950 Structural use of steelwork in building.
    • BS 5950-2:2001 Specification for materials, fabrication and erection. Rolled and welded sections.
  • BS 8206 Lighting for buildings.
    • BS 8206-2:2008 Code of practice for daylighting.
  • BS EN 10143:2006 Continuously hot-dip coated steel sheet and strip. Tolerances on dimensions and shape.
  • BS EN 10346:2009 Continuously hot-dip coated steel flat products. Technical delivery conditions.
  • BS EN 12056 Gravity drainage systems inside buildings.
    • BS EN 12056-3:2000 Roof drainage, layout and calculation.
  • BS EN ISO 10211:2007 Thermal bridges in building construction. Heat flows and surface temperatures. Detailed calculations.
  • BS EN ISO 13788:2002 Hygrothermal performance of building components and building elements. Internal surface temperature to avoid critical surface humidity and interstitial condensation. Calculation methods.
  • MRCMA Technical paper 14. Guidance for the design of metal roofing and cladding to comply with Approved Document L2: 2001
  • TM 37: Design for improved solar shading. 2006

Performance

Performance data for the Twin-Skin Systems: AS Series Roof & Wall Profiles’ covers tables for wind suction, imposed load and drifting snow load for all the available colours and thicknesses of roof and wall profiles. It also includes profile dimensions, the durability and the life to first painting of the plastisol coated profiles, fire resistance results, thermal conductivity and the effects of biological attack.

Steel profiles

Standard external weather sheets are available in 0.5mm and 0.7mm thicknesses; the AS20/1000 liner sheet is available in 0.4mm and 0.7mm thicknesses.

Tables 01 and 02 give the standard profile dimensions, weights, and manufacturing tolerances.

For technical and performance details of all profiles click here.

The steel used in the AS series roof and wall profiles is hot-dip galvanised to BS EN 10346:2009 or Aluzinc coated, then finished with one of the coatings listed in Table 03 or one of an equivalent quality.

Weather sheets are available in a number of different profiles, many with matching roof and wall profiles.

In order to maintain our high standards of customer service we may replace the steel listed here with that of similar quality from different suppliers.

Table 01: Profile dimensions

Cover
AS13/3 990mm
all other panels 1000mm
Standard lengths 1000 – 12000mm
(others available on request)

 

Weight
0.4mm thick 3.49 kg/m2
0.5mm thick 4.57 kg/m2
0.7mm thick 6.49 kg/m2

Table 02: Manufacturing tolerances

Cut to length: L < 3m +/- 5mm
Cut to length: L > 3m +/- 10mm
Cover width -0mm / +3mm
End square -3mm / +3mm

Table 03: Twin-Skin Steel Cladding coatings

Weather Sheet 200LG 200 micron PVC Plastisol A high performance pre-painted steel system on a hot dipped galvanised substrate. The outer face is finished with a leather-grain embossed PVC while the inner face is finished with a heat cured epoxy paint system.
Dobel Nova A 50 micron thick acrylic polymer coating which has high wear resistance, excellent colourfastness and good flexibility. The coating contains no PVC or Isocyanates and the material is wholly recyclable.
Polyester A polyester coating with a medium term life.
Corus HPS200 A durable organic coating with Scintilla finish on a substrate treated with hot-dipped zinc-aluminium alloy.
Corus and Dobel PVDF A 27 micron thick stoved flurocarbon coating: excellent colour stability at temperatures as high as 120ºC.
Liner Sheet White lining enamel Single coat, 18 micron thick finish offers an easy to clean surface. Standard colour ‘bright white’.
200LG Plastisol 200 micron thick coating for areas with high internal humidity or a corrosive environment.
Dobel Foodsafe 150 micron coating, suitable for the interiors of cold stores, food processing buildings and other hygiene applications.

Construction Details

Common roof, wall and rooflight details for the Twin-Skin Steel Cladding Systems. The details contained in the PDFs are the coloured versions shown on pages 23 to 40 in the ‘Twin-Skin Systems: AS series Roof & Wall Profiles’ ‘ technical brochure.

These sheets are available for download in PDF format:

Design details – Roofs

Common details for the Twin Skin Roof Systems.

Design details – Walls

Common details for the Twin Skin Wall Systems.

Design details – Rooflights

Common details for fitting site assembled, in-plane rooflights to Steadmans Twin Skin Roof Systems.

AS Twin-Skin Steel Cladding profiles are available directly from Steadmans. AS Twin-Skin Steel Cladding profiles are supplied in plastic wrapped packs: fully timber crated packs are available for sea freight shipping at additional cost.

AS Twin-Skin Steel Cladding profiles are usually delivered to site. Off loading is the responsibility of the customer. Delivery by self off-load vehicles can be arranged.

ONE ORDER • ONE DELIVERY • ONE INVOICE • ONE NUMBER • 01697 478 277

Handling and storage

AS profiles are delivered to site in packs. Packer sheets are used at the bottom of the packs to provide protection and the ends of the packs are wrapped with plastic. Maximum pack weight is 2 tonne.

The packs can be off-loaded directly to the roof, or to a storage area, which should be dry and well away from traffic. Packs may be stacked using suitable wooden bearers and packers. Bearers should be placed above each other.

Handle AS profiles carefully to avoid marking weather sheets or liners. Lift sheets from the pack – do not drag them. Observe site health and safety procedures and the results of manual handling and other assessments.

Preparation

Before fixing any sheets check the squareness and accuracy of the steelwork. Determine the direction of the prevailing wind. Check sheets for damage before fixing.

Installation

There are two methods for installing the AS Twin-Skin Steel Cladding system:

  • working across the roof building up the whole system in one pass, or
  • laying the liner across the whole roof, then laying the
    insulation and weather sheet. Using 0.7mm AS20/1000 or AS30/1000 as a liner will give a non-fragile roof which makes the rest of the installation process safer, and enables a higher standard of installation.

The following installation guidance presumes the second method.

Roofs – general sequence

Observe the general installation sequence:

  1. Lay liner sheet (see laying sequences for sheets below). Seal side laps with 50 × 1mm polyband tape.
  2. Assemble and fix support rails and brackets.
  3. Lay insulation in a continuous layer.
  4. Lay and fix weather sheet (see laying sequences for sheets below).
  5. Fix flashings. Use foam filler pieces and butyl sealant to form weather tight junctions.

Roofs – single tier laying sequence

The following sequence applies to weather sheets on single tier roofs:

  1. Lay the first sheet with the female edge to the gable, away from the prevailing wind. Use a string line to lay the sheet straight and true. Fix the sheet.
  2. Apply butyl sealant along the top of the male crown. The surfaces receiving the sealant must be dry: joints in the sealant must be lapped by 25mm not butted.
  3. Lay the second sheet with its female crown over the male crown of the first sheet. Fix the sheet.
  4. Stitch the lap with self-drilling fixings.
  5. Continue to lay sheets across the roof, checking the alignment of the sheeting and correcting any deviations.

Roofs – double tier laying sequence – liner sheets

On a double tier roof lay the liner sheets in the order shown in figure 40.

  1. Lay liner sheet one with the female edge to the gable, away from the prevailing wind. Use a string line to lay the liner sheet straight and true. Fix the liner sheet at every purlin except the top one.
  2. Apply a single run of 4mm diameter butyl sealant to the head of liner sheet one (figure 41).
  3. Lay liner sheet two with its female edge to the gable and the tail lapping the head of sheet one. Fix the liner sheet.
  4. Lay liner sheet three with its female crown lapping the male crown of sheet one. Fix the liner sheet at every purlin except the top one.
  5. Apply a single run of 4mm diameter butyl sealant to the head of liner sheet three (figure 42).
  6. Lay liner sheet four with its female crown lapping the male crown of sheet two and its tail lapping the head of sheet three. Fix the liner sheet.
  7. Apply a run of 50mm polyband sealant tape along the side lap of liner sheets one and three and liner sheets two and four (figure 43).
  8. Continue to lay the liner along the roof, checking the alignment of the sheeting and correcting any deviations.

Roofs – double tier laying sequence – weather sheets

On a double tier roof lay the weather sheets in the order shown in figure 40.

  1. Lay weather sheet one with the female edge to the gable, away from the prevailing wind. Use a string line to lay the sheet straight and true. Fix the sheet at every purlin except the top one.
  2. Apply two runs of 6 × 5mm butyl sealant to the head of weather sheet one and a run of butyl sealant to the male crown for the length of the lap (figure 44).
  3. Lay weather sheet two with its female edge to the gable and the tail lapping the head of sheet one. Fix the sheet.
  4. Apply a run of butyl sealant to the male crown of sheets one and two (figure 45).
  5. Lay weather sheet three with its female crown lapping the male crown of sheet one. Fix the sheet at every purlin except the top one.
  6. Stitch the side lap with self-drilling fixings.
  7. Apply two runs of 6 × 5mm butyl sealant to the head of weather sheet three and a run of butyl sealant to the male crown for the length of the lap. Ensure the sealant laps the run on the male crown of sheet two (figure 46).
  8. Lay weather sheet four with its female crown lapping the male crown of sheet two and its tail lapping the head of sheet three. Fix the profile.
  9. Stitch the side lap with self-drilling fixings.
  10. Continue to lay the sheet along the roof, checking the alignment of the sheeting and correcting any deviations.

Walls – general sequence

Observe the general installation sequence:

  1. Fit liner sheets with temporary screws (see sequences for liner sheets above).
  2. Assemble and fix support rails and brackets.
  3. Fit insulation in a continuous layer: clip in place until the weather sheets are installed.
  4. Fit and fix weather sheets (see sequences for weather sheets above).
  5. Fix flashings. Use foam filler pieces and butyl sealant to form weather tight junctions.

Walls – laying sequence

The following sequence applies to weather sheets on walls:

  1. Set sheet one upright against the framing at the corner of the building with the female edge to the corner. Make sure the profile is vertical.
  2. Fix with one fixing in alternate valleys at each rail.
  3. Apply a run of butyl sealant along the male crown.
  4. Set sheet two upright with its female edge lapping the male edge of sheet one.
  5. Fix the sheet.
  6. Stitch the lap with self-drilling fixings (weather sheets only).
  7. Continue to lay sheets along the wall, checking the alignment of the cladding and correcting any deviations.

Cutting profiles

Where profiles have to be cut on site:

  • Use a powered reciprocating saw or circular saw. Do not use an abrasive wheel.
  • Support the profile along the line of the cut.
  • Protect the pre-coated finishes of the profile.
  • Clean any swarf or debris from the pre-coated finish of the profile immediately.

Completion

When all the sheets have been installed check:

  1. All fixings are correctly fitted and tightened
  2. The fixings do not distort the profile
  3. All fixing caps are fitted
  4. Minor scratches have been treated
  5. The surface of the roof is clean and free of any swarf or debris

Annual inspection

It is good practice to carry out an annual inspection of the building exterior and to carry out any remedial work identified during the inspection, see table 31.

Touch-up

Minor scuffing to the colour coating should not be treated. Deeper scratches which reach the substrate should be repaired with touch-up paint.

The touch-up paint should only be applied to the original scratch using a fine paint brush. As touch-up paint will dry to a slightly different colour than the original coating the area which is touched up should be kept as small as possible.

Table 31: Checklist for annual inspection

Check for: Remedial action:
Blocked gutters, which may cause overflow into the building. Clean gutters and wash out any blockage.
Build-up of debris, which can retain water and cause corrosion. Remove debris.
Dirt retention on areas not washed by rainwater: that affects the appearance of the building and, if left untreated, could cause the coating to breakdown. Wash down with fresh water using a hose and soft bristle brush. Heavy deposits can be removed with a solution of water and household detergent or proprietary cleaner.
Mould growth, which is rare, but can affect the appearance of the building. Wash down, then apply a cleansing solution: consult Steadmans Technical Department for guidance.
Local damage – breakthrough of the panel coating could result in corrosion of the substrate. Assess the extent of the damage and either touch up (see opposite) or overpaint the affected area or replace damaged sheets.
Drilling swarf and fixing debris. Remove debris.
Condition of fixings – faulty fixings can cause leaks or rust staining on the surface of the panels. Replace faulty fixings and missing clips.
Corrosion of cut edges. Cut or abrade edges back to clean bright metal and repaint: consult Steadmans Technical Department for guidance.

Associated Projects

Fixings

Steadmans supply a bar and bracket spacer system for installing the liner and weather sheet, as well as a full range of fixings.

Insulation

Mineral or glass wool insulation can be used to provide appropriate fire, thermal and acoustic performance.

Gutters

Steadmans manufacture and supply a range of gutters to match the profiles.

Gutters are produced from a variety of materials including pre-galvanised steel (to BS EN 10143:2006) and pre-coated steel, either painted or PVC-coated on one or both sides; aluminium can be supplied to order. Complete gutter systems and accessories can be manufactured to specification, up to 10m long and 3mm thick: contact Steadmans’ sales office for details of sizing.

Flashings

Steadmans manufacture a range of flashings to match the profiles in Plastisol leathergrain, polyester, Nova, Scintilla, galvanised, or PVDF finishes. Flashings can be supplied in lengths up to 6m in traditional profiles, or can be shaped to meet special customer requirements.

Sealants

Steadmans supply a range of NFRC Class A butyl sealants, profile foam fillers and expanding foams to enable profiles to be sealed to each other and to other building components, so avoiding thermal bridging and air leakage.

Rooflights

Steadmans offer a range of site assembled in-plane rooflights to match the dimensions of AS Twin-Skin Steel Cladding profiles (see table 27). Triple skin site assembled rooflights are available for projects where U-values of 2.2W/m²K* are required: they consist of two skins of GRP, which are installed with the liner and weather sheets, and an intermediate insulating layer of polycarbonate. Twin-Skin Steel Cladding rooflights may be used on projects where higher U-values are acceptable.

Rooflights can be supplied to meet project requirements for light transmission, durability, non-fragility rating and fire resistance: contact Steadmans’ sales office for details.

Property Units Value
Minimum slope ° 6
Maximum length m 7
Width (centre-centre) mm 1000
U-value W/m2K 2.2*

*Figures supplied by Brett Martin Daylight Systems Ltd. Other manufacturer’s figures may vary.

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