FAQs

» HardieBacker® cement board provides a stable, water resistant substrate and a strong surface to bond tile to.

» Although both products can be used on floors, walls or worktops, HardieBacker® 250 cement board is primarily used on floors, because the thinner board decreases the transition to the other floor surfaces. HardieBacker® 500 cement board is primarily used on walls to match up to the 12.5 mm plasterboard and to provide improved impact resistance. It also has a high load carrying capacity so will support the weigh of heavy natural stone products better.

» It is made of Portland cement, ground sand, cellulose and selective additives. It contains no asbestos, formaldehyde, gypsum or glass fibre.

» It can be installed anywhere in your home where ceramic or natural stone tiles are to be applied over timber floors or on studwork walls. HardieBacker® cement board is suitable for use on interior floors, walls and worktops.

» Yes. HardieBacker® backerboard is water resistant and immune to water damage. It won't rot, swell or warp.

» Yes. However If you are installing HardieBacker® 250 cement board on the wall, you must ensure that all the edges of all boards are fully supported on battens. This will increase the supporting structure significantly, but is necessary if the product is to perform correctly.

» The primary function of HardieBacker® cement board is to provide a water resistant flat surface to tile on; it is not designed for use over concrete. The minimum sub-floor specified is 15.8 mm exterior grade plywood sub-flooring with a deflection not greater than 3mm for live and dead loads over joists that do not exceed a span of 400 mm centres.

» We recommend installing the grid side up on HardieBacker® 250 and the smooth face up for HardieBacker® 500 cement board, as these surfaces have been especially treated to receive the tile adhesive.

» Cementitious tile adhesive is specified between the HardieBacker® cement board and the sub-floor to eliminate any deviations between our product and the sub-floor. This decreases the probability of popping or cracking tiles due to deflection and air pockets.

» The tape will tie the sheets of HardieBacker® cement board together helping to disperse any movement of the substrate and therefore decreasing the probability of popping or cracking tiles along the seams.

» The screws that you are using do not have the power to rout out the material in order for the screw head to sit flush. Be sure to use HardieBacker® cement board screws for wood or metal, as they are specifically designed for the job. If you continue to have difficulties, we recommend switching to galvanised clout nails.

» Fix HardieBacker® cement board sheets with HardieBacker® screws for wood or for metal (as the substrate dictates) every 200 mm around the perimeter and on all supporting studs. Keep fixings 15mm from sheet edges and 50 mm in from sheet corners.

» No. HardieBacker® cement board is not suited to this type of fixing application.

» Yes, HardieBacker® cement board is suitable for under floor heating. It should always be placed between the structural timber floor and the heating element. Never place heating under HardieBacker® cement board, as there is a risk of damaging the system when fixing it down.

» We recommend HardieBacker® 500 cement board as it is more suited to wall applications. If you need to fix HardieBacker® 250 cement board to a wall please contact our UK Customer Service on 0800 068 3103.

» Floors - maximum deflections:
When installing ceramic tile – L/360
When installing natural stone – L/720

Okay, you are now going to have to do some simple math’s. Sorry, but it will be worth it.

To calculate the deflection in any floor you plan to tile take the width of the room in mm (L in the above formulae) and divide it by either 360 if you are laying ceramic tiles or 720 if you are laying natural stone. (Generally speaking natural stone is more brittle and less tolerant of floor deflections). Record this figure in mm. This is how much your floor can deflect without causing a problem to the tiling. e.g. a 2400mm width room divided by 360 for a ceramic tile = 6.6mm deflection across the whole floor.

Now you need to measure the deflection you will actually have in your room:
Take a string or strong fishing line and pull in tight from wall to wall across the middle of the room. Anchor it by driving in a nail or screw each side and tying it off. It must be tight. Now measure any dip from the string to the top of the floorboards in mm and record the figure. Next, place a weight in the centre of the room equivalent to the maximum anticipated load for the room (for example a couple of adult family members would work in a bathroom and don’t forget the weight of the tiles, adhesive and grout), now re-measure the deflection from the string and record it. Next deduct the original unloaded measurement from this one to see how much the floor has deflected under load. If this figure is greater than the width divided by 360 or 720 in mm in your original calculation then the floor must be stiffened up to prevent tiles from cracking in the future. If it is less then you should be okay to carry on installing your HardieBacker. So for example: the unloaded measurement = 4mm,the loaded measurement = 8mm. 8mm minus 4mm = 4mm deflection under load. Your original calculation gave you a maximum allowable deflection of 6.6mm so you should be okay to continue.

Please note it only takes a small amount of movement in a floor to crack a tile so it is important that movement is reduced below the stated figures before tiling commences. A bath or washing machine full of water is heavy; do not underestimate how much this can deflect the floor.

» HardieBacker® cement board is available from most leading builders merchant and tile shops. Please check the Locate a Dealer section of our website to find the supplier nearest to you. If you have any difficulties obtaining the product please contact our UK Customer Service department on 0800 068 3103.

» Your local HardieBacker® cement board stockist can provide you with a HardieBacker® Score-and-Snap Knife. Please check the Locate a Dealer section of our website to find the supplier nearest to you.

» See your local HardieBacker® cement board stockist, or call UK Customer Service on 0800 0683103.

» Yes, in some situations. The boards must be fully bedded on a 6mm notched trowel bed of flexible tile adhesive. The wall should then be drilled and plugged and the boards fixed back to the wall with a suitable screw. (See our Technical Fixing manual for details).

» No. While HardieBacker® cement board is an interior non-combustible product, it is not a fire protection board, and therefore it is not recommended or warranted for these applications.

» No. The primary function of HardieBacker® cement board is to provide a water resistant flat surface to tile on; it is not designed for use over concrete.

» Yes, HardieBacker® cement board can go over linoleum or vinyl composite tile. Even though you may go over vinyl composite tile, James Hardie does not recommend you install HardieBacker® cement board over cushioned vinyl. Follow HardieBacker® cement board floor installation instructions for complete details. However, it is much better to remove all existing floor coverings and fix the HardieBacker® cement board direct to the substrate.

» No. HardieBacker® cement board is not a waterproof board. You should seek professional advice regarding the waterproofing of cellar walls and floors.

» No. HardieBacker® cement board is not suitable for external use, however we do have products suitable for external applications. If you have an external application requirement, please contact our UK Customer Service on 0800 0683103.

» HardieBacker® backerboard should be cut using HardieBacker® score-and-snap knife, available from your HardieBacker® cement board stockist.

» No. HardieBacker® cement board is ready to tile once installed, just wipe it down with a damp cloth to remove any dust prior to tiling.

» Yes. However, occasionally it may be necessary to paint a wash coat of diluted PVA (diluted with water to about the consistency of skimmed milk) over the boards once installed to prevent the water being drawn out of the plaster too quickly during application. Applying PVA to HardieBacker® cement board will slow down suction allowing you to "work" the plaster to a smoother finish. The wash coat should be allowed to become tacky (a few minutes in normal temperatures) before plastering commences. We suggest that a small discrete area be tested first for workability of the plaster before application of the wash coat. PVA is available from any good builders merchant.

Please note if the wash coat is allowed to dry, is not diluted sufficiently or too much is applied then it may seal the face of the HardieBacker permanently which will prevent the plaster from bonding to it — think in terms of trying to plaster over wall sealed with gloss paint, it will not work, the plaster will dry out and fall off. The surface of the HardieBacker must be slightly porous for plastering to be successful.

» Yes, HardieBacker® cement board is suitable for a wide range of paint coatings. We do however recommend that you plaster the board first, to ensure the best possible finish.

» We sell a range of specialist tools designed to cut our products quickly, effectively and with a minimum of dust. The best are hand tools like the score-and-snap knife and HardieGuillotine™ both of which are available from your distributor. Always use approved safety glasses and appropriate EN approved respiratory protection (PPE #2 or #3) for particulate hazards when working with HardiePlank® siding and HardieTrim™ siding.

» Yes. All cut ends on HardiePlank® siding should be painted with our ColorPlus® touch-up paint. This prevents unwanted water ingress into the cut edge.

» There are approximately two planks to the square metre. Measure the width and height, in metres, of each wall to be clad. Multiply the two dimensions together to give you the area in square metres of each wall and then multiply this total by two to give you the total number of planks for each wall. Add all your walls up and this will be a reasonable guide to how many planks you need to order.

» No. There is no need to pre-drill HardiePlank® siding for either nail or screw applications.

» You can use Impulse or pneumatic nail guns as well as nailing by hand. Nails should be placed 20-25mm down from the top edge of each plank and driven into the batten with the heads flush with the surface of the plank.

» Planks should be overlapped 30mm leaving a visible margin of 150mm.

» Planks should be butt jointed over a batten. Do not joint planks between battens as this could lead to failure of the product. Some rainwater may penetrate the butt joint, and whilst this is not a problem in itself as the system operates as an unsealed rain screen, it is good building practice to provide protection to the batten reducing the risk of the batten rotting over time. This can be easily achieved by fixing a small piece of EPDM tape on the batten at the point where the boards will abut each other (see installation guide for details). Alternatively a small bead of transparent general mastic placed at the line of the joint will perform a similar function. Any excess should be wiped off the face of the plank immediately.

» A clearance of 150 mm should be maintained between the bottom edged of the lowest layer of HardiePlank® siding and any unpaved ground. This will allow for clearance when soil is back-filled against the foundations and footings and prevent the bottom plank being damaged by contact with soil and rainwater splashing up the wall.

» HardieTrim™ siding is the preferred trim material for use with HardiePlank® siding. HardieTrim™ siding has the durability and paint holding characteristics to match the proven performance of HardiePlank® siding. Other trim materials may be used; however some of these may need a more intensive maintenance program.

» Yes. The use of a weather resistant barrier reduces the potential for the entry of moisture into the exterior wall of the building. It is good building practice.

» Any weather-resistant membrane complying with BS-EN1521 and having a vapour resistance of 0.6 MNs/g is acceptable.

» Yes. Apply a sheathing layer of OSB or marine plywood followed by, a weather resistant membrane and timber battens over the face of the metal frame, and install the HardiePlank® siding as per the installation instructions. The site engineer should ensure that the fixing specification of the sheathing and battens to the steel studs sections satisfies the engineering demands placed on the structure.

» Straight cuts:
we recommend using a HardieBlade® saw blade for use with circular saws.

» Curved cuts or pipe cut outs:
a Jig Saw fitted with a TC tipped blade. Typical reference numbers for these are Bosch T141 and Hitachi JA10.
It is possible to cut the board with hard point hand saws but they will become blunt very quickly.
Under no circumstances should the product be cut with high speed continuous tools like hand grinders or disc cutters.
In all cases cut the panels with the face side up.

» Yes. All cut ends on HardiePanel® siding should be painted with our ColorPlus® touch-up paint. This prevents unwanted water ingress into the cut edge.

» Yes. HardiePanel® siding can be supplied pre-primed for on site painting. It is called PrimePlus®. You'll need to paint within 90 days after installation.

» Any good quality external grade acrylic paint can be applied to HardiePanel® PrimePlus® siding.

» 150mm.

» No. Most nails or JH colour matched Torx screws can be used without pre drilling.

» At the edges fixings should be 50mm in from a horizontal edge and 15-20mm in from a vertical edge. The vertical spacing of fixings is determined by the local wind load characteristics and can range from 300mm to 600mm. We seriously advise that you check with an engineer to determine the specific fixing spacing's for your project.

» Horizontal joints should be finished using the James Hardie® Metal-Trim Horizontal Joint Profile.
Vertical joints can be either left open (Express joints) with EPDM TAPE on the battens or covered with a length of HardieTrim® profiles or connected with an H profile (available from other suppliers).

» The plastic film helps protect the finish from damage during transportation, storage and installation. We would suggest that it is removed last thing from the top edge down as the fixings are inserted.

» Yes. Apply a sheathing layer of OSB or marine plywood followed by, a weather resistant membrane and timber battens over the face of the metal frame, and install HardiePanel® siding as per the installation instructions. The site engineer should ensure that the fixing specification of the sheathing and battens to the steel studs sections satisfies the engineering demands placed on the structure.

» Any weather-resistant membrane complying with BS-EN1521 and having a vapour resistance of 0.6 MNs/g is acceptable.

» 600mm, but this should be checked by a qualified engineer as this is linked with your local wind loads.