Hardiplank® Siding is a nominally 8 mm thick plank intended as a horizontal exterior cladding for residential and light commercial buildings.

Harditrim® Siding is a nominally 25 mm thick plank intended as a nailable decorative siding for residential and light commercial buildings.

The plank and trim are fixed to timber battens over a timber frame or masonry walls using corrosion-resistant nails or screws.

This product is intended for use in residential and light commercial buildings

3.1 Composition
The plank and trim are made from Portland cement, ground sand, cellulose, and selected additives. They contain no asbestos, formaldehyde, gypsum or glass fibre.

3.2 Characteristics
Product: Hardiplank® Siding Harditrim® Siding
Nominal Thickness: 8 mm 25mm
Nominal Length: 3600 mm 3050mm
Nominal Width: 180 mm 90 mm, 140 mm, 185 mm
Nominal Weight: 11.23kg/m˛ 21.97 kg/m˛

3.3 Production controls

The Hardiplank® Siding product has been evaluated in accordance with the protocols and acceptance criteria of ISO 8336:1993 (E) and was found to be compliant, per evaluation report no. 3035670 (December, 31, 2002).

3.4 Associated products.

3.4.1 Screws

For screw fixing use a screw with a shank minimum 4.6 mm diameter x minimum 32 mm long with a minimum 9.5 mm head diameter with countersinking ribs formed on the underside of the head to facilitate the embedment of the screw in the face of the siding. The screw should have adequate provision for corrosion resistance, refer to Section C.6.4 of BS 4072:1999, Copper/ Chromium/Arsenic preparations for wood preservation.

3.4.2 Nails
A hot dipped, galvanised clout head, plain shank nail minimum 40 mm long, minimum 3 mm shank diameter and minimum 9.5 mm head diameter manufactured to the requirements of BS 10230-1:2000 can be used to fix the Hardiplank® siding to the treated timber wall battens if the battens are expected to be only occasionally damp.

If the treated timber is likely to become wet and a long service life is required, fixings of austenitic stainless steel should be used in preference to other fixings.

Ref: Section C.6.4 of BS 4072:1999, Copper/Chromium/Arsenic preparations for wood preservation

3.4.3 Timber wall battens
Timber wall battens are fixed in the vertical orientation to the outer face of the structural wall at 400 mm or 600 mm centres. The timber grade and treatment type needs to be consistent with the engineering requirement for exterior timber as required by the local building regulations. The timber thickness should not be less than 25 mm thick. When fixing over a masonry wall a thicker batten is required to accommodate the 40 mm minimum length of the siding fixing nail.

3.4.4 Building paper
The building paper shall comply with the requirements for a Type 1 flexible building membranes (breather type) as described in BS 4016: 1997.

3.4.5 Sealant
Where sealant is required for joint, use a sealant selected in accordance with the recommendations with BS 6213:2000, Selection of Construction Sealants guide, and apply as per manufacturer’s instructions.

4.1 Structure.
The structural wall to which the HardiplankĆ Siding and HarditrimĆ Siding is to be fixed, must be of sufficient strength and stiffness to satisfy the requirements of the local building regulations in its own right under the design dead, live and wind loads. The wall may be of masonry or framed construction.

4.2 Building paper
Fix a building paper, as described in section 3.4.4, to the outer face of the structural wall, laid along the wall, with an overlap between the layers of building paper of at least 150 mm. Ensure the building paper is lapped to drain any water to the outside of the building.

4.3 Timber wall battens
Fit the timber battens onto the exterior of the wall surface over the building paper. The battens are fitted vertically at 400 mm or 600 mm centres aligning with the structural wall studs. Ensure that the ground clearance required by the local building regulations is maintained.

4.4 Fixing the wall battens to the structure
The battens must be securely fixed to the structural wall as they transfer the wind load applied to the Hardiplank® Siding to the structure. Ensure that the batten selection and fixing meets the local building regulation requirements and the wind load requirements of BS 6399: Part 2, 1997.


5.1 Starter strip
Cut a 25 mm wide x 8 mm thick strip from a length of Hardiplank® Siding, see figure 1. Nail this along the front face of the battens so the the lower edge of the starter strip lies along the line made by the bottom of the vertical battens. This provides the lap spacing for the first row of plank. The omission of this strip will result in “kick-out” on the wall appearing inconsistent in the second, third and fourth courses.

5.2 First row of Hardiplank® Siding
Mark a line 170 mm up from the lower edge of the starter strip, see figure 1. Ensure that this line is level. This will be the top of the first row of Hardiplank® Siding. This spacing gives a 10 mm drip edge at the lower edge of the siding.

Fix the siding to the vertical timber battens using the fixings described in sections 3.4.1 and 3.4.2. Fix the siding to every vertical batten with one nail or screw. The centre line of the nail or screw should be 20 mm below the top edge of the siding. Refer figure 2. When fixing the ends of the siding ensure the fixing is placed between 9 mm and 12 mm from the end.

5.3 Second and subsequent rows of plank
The second row of plank is placed so that the lower edge of the second plank overlaps the top of the first plank by 30 mm, see figure 2, 3 and 4. It is important to carefully maintain this dimension throughout the construction of the wall. Fix the plank using the same type of fasteners and method as the first plank.

Stagger the butt joints between pieces of siding in an area of wall over two or more batten lines, i.e. avoid joints located directly in the same vertical line. Refer to figure 5.

5.4 Plank joints
Cut the siding plank neatly so that it finishes at the centre line of the timber batten. The siding planks are butted in moderate contact to form the joint. Optionally install the planks with a 3 mm gap between the ends of the siding planks and fill the gap with a sealant complying with BS 6213. See section 3.4.5. Fix the siding into position taking care to maintain the 30 mm overlap dimension between each row of siding planks. James Hardie believes it is good building practice to seal the joints around windows, doors and trim edges to prevent moisture, such as wind driven rain and snow, from penetrating the wall cavity.

5.5 Plank joints.

5.5.1Hardiplank® Siding

Where planks need to be cut to achieve the installation requirements, it is recommended that a score and snap knife be used. The procedure when using this tool is;

  Mark the line to be cut on the face of the plank
  Place a straight edge along the line to guide the score and snap knife
  Score along the line until a groove of 3-4 mm is made in the face of the sheet. This may take 2 or 3 firm passes of the knife
  Break the plank by holding one piece firmly and make the break by snapping the other piece with an upward motion.

Another option is to cut using a circular saw fitted with a HARDIBLADE™ saw blade.

5.5.2 Harditrim® Siding

Where Harditrim® Siding needs to be cut use a circular saw fitted with a HARDIBLADE™ saw blade.

5.6 Corners

The wall battens should be fitted so that they overlap at the corner forming a solid corner to which to fix the Hardiplank® Siding and Harditrim® Siding.

The corner construction is completed using Harditrim® Siding see figures 6 & 7. The corners can be formed in two ways depending on the style desired;

(i) The Hardiplank® can be run right to the corner and have the Harditrim® Siding placed over the Hardiplank® Siding, or

(ii) The Harditrim® Siding can be fixed to the corner battens directly and the Hardiplank® Siding butted up to the edge of the Harditrim® Siding.

Allow approx. 3 mm between the end of the Hardiplank® Siding and Harditrim® Siding for the application of sealant.

The Harditrim® Siding can be butt joined or mitre cut at the corner. NOT HERE

Hardiplank® Siding and Harditrim® Siding can be field finished. For field finishing paint in accordance with the paint manufacturers written application instructions. Hardiplank® Siding and Harditrim® Siding may be available prefinished.

When a penetration in the wall is required, for a pipe or tap for example, form a hole in the plank using a hole saw. Make the hole approx. 8 mm larger than the diameter of the pipe. Seal between the fitting and the edge of the hole with an exterior quality sealant. If the space between the fitting and the hole is too wide, use a polyethylene foam backing rod to fill the major part of the gap. The remaining gap should be filled with sealant..

Hardiplank® Siding and Harditrim® Siding are not intended as a load bearing or shear elements in the wall construction. Items required to be attached to the wall should be supported directly by connections to the structural sheathing and/or framing members, not attached to the siding or trim as the primary load bearing elements.



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Last modified: October 09, 2006