Frequently Asked Questions

Thermal modification is a conceptually simple process - suitable timbers are subjected to high temperatures using heat and steam in a controlled environment without the use of any chemicals. Once the process is complete, the equilibrium moisture percentage of the modified product is around 4-7%.

• TMT Taiga has rich warm brown tones and “butterfly knots” showing up at regular intervals that give cladding and interiors a completely unique personality.
• TMT Taxon has a soft, even-grained appearance with minimal knots and a variation of deeper chocolate tones.
• While TMT Tuscan is the lighter, clearer grade option. It has a uniform light golden brown colour.

• Dimensional stability - Excellent dimensional stability through reduced moisture absorption and modified cell structure. Able to accept darker coatings with significant reduction in dimensional movement.
• Durability - Proven durability through a lowered moisture content and the removal of the food source during the TMT process, ensures low susceptibility to fungal decay.
• Responsibly sourced and non-toxic - Premium quality that is responsibly sourced. There is no presence or release of added toxic substances during the building life.
• Certified premium quality - Truly natural product with certified quality; all JSC TMT® products are sourced from reliable and world-renowned suppliers that are leaders in the timber thermal modification process.
• For all climates - Proven to work well, even in the most challenging climates. More stable in humid conditions.
• Beautiful grade & finish - Whether a feature or clearer grade, all JSC TMT® options come in beautiful rich brown tones and take oil and water-based coatings well, including dark colours.

Yes. The thermal modification process does not change the combustibility of the timber.

JSC Thermally Modified timber is a softwood truly sustainable, durable, stable alternative to tropical hardwoods.

Yes, like any other timber, the thermally modified timber cladding has to be sealed on all four sides before installation.

Yes. Thermal modification is an environmentally friendly process. It is a chemical-free process that uses only heat and steam.

Thermal modification is an environmentally friendly process resulting in an exceptionally stable, highly durable, and aesthetically pleasing timber – all desirable properties for bespoke cladding profiles.

Thermal modification is a conceptually simple process - suitable timbers are subjected to high temperatures using heat and steam in a controlled environment without the use of any chemicals. Once the process is complete, the equilibrium moisture percentage of the modified product is around 4-7%.

The thermal modification process permanently alters the cell structure which enhances the physical properties of the timber. The result of this is that the timber has a greatly reduced capacity to absorb moisture. With the reduction of moisture absorption, the timber is much less susceptible to cupping, expansion, contraction, or distortion caused by seasonal changes in the environment. Due to the thermally modified process that the timbers undergo, all the sugars and tannins in the wood are baked, removing the food source from fungi and insects as well as hardening and darkening the wood. You will see all TMT options come in rich brown tones and are suitable for a variety of interior and exterior applications such as exterior claddings, interior linings, battens, and more depending on the species you choose

• Enhanced durability and exceptional dimensional stability

• Able to accept darker coatings with a significant reduction in dimensional movement

• Low susceptibility to fungal decay

• Consistent, aesthetically pleasing colour

• Easily workable and easy to maintain

Yes, JSC are happy to provide samples of the species, profile, and even wood oil colours to ensure you get the desired outcome for your build. Send us an email with your request or pop into one of our branches to discuss your requirements!

Yes, JSC has years of experience when it comes to custom and architectural profiles to suit a range of styles and designs. There can be limitations based on things like quantity and weatherproofing considerations so talk to our technical team to discuss options!

The technical drawings are exactly the same on both sets. The main difference between them lies in their layout and purpose:

• A3/A1 Architectural Drawings:

These drawings group similar details together on larger A1 or A3 pages. They are designed to make it easier for architects, designers and specifiers to access and reference grouped details. For instance, all window details, meter box details, and corner details might be presented together on a single A1 or A3 page.

• A4 Site Drawings:

Each detail is presented on individual A4 pages. These drawings are specifically tailored for builders on-site. The larger scale of each detail on its own A4 page makes it easier to read and distribute the drawings at the construction site.

Yes, like any other timber, the thermally modified timber cladding has to be sealed on all four sides before installation.

Yes, for further information on this please see our Codemark certificates available from our downloads section, for each of the main cladding systems.

Yes, JSC are happy to provide samples of the species, profile, and even wood oil colours to ensure you get the desired outcome for your build. Send us an email with your request or pop into one of our branches to discuss your requirements!

Yes, JSC has years of experience when it comes to custom and architectural profiles to suit a range of styles and designs. There can be limitations based on things like quantity and weatherproofing considerations so talk to our technical team to discuss options!

From New Zealand history, Bevel Back weatherboards are one of the most traditional cladding types in the country, from the bungalows around 1990s, to 1940 -1960s houses, the buildings would typically have this cladding, while villas from the 1880s would be mostly clad in rusticated weatherboards.

Nowadays, Vertical Shiplap weatherboards are considered one of the most popular timber cladding profiles.

Yes, this generally requires a custom weatherboard profile. JSC are specialists when it comes to curved weatherboard solutions so contact our team today to discuss your options.

For exterior timber JSC always recommends the use of Band Sawn Face over dressed face finish. Band sawn face allows for far greater coating absorption and thus greater lifespan of the chosen coating. As dressed face timbers have the pores of the timber closed off in machining it makes it much harder for coating to penetrate the surface. Today’s bandsawn finishes are much finer than those of previous years and still provide a modern, high quality aesthetic to even the most discerning build.

Vitex is sustainably sourced from community-based operations in the Solomon Islands. More here

Yes, Vitex’s durability and aesthetic appeal make it ideal for both residential and commercial decking and exterior structures.

Yes, JSC’s Premium Garapa is FSC® certified, ensuring that it comes from responsibly managed forests.

Garapa offers a more cost-effective alternative to other hardwoods while still providing excellent durability and aesthetic appeal.

Yes, JSC Purpleheart is FSC® certified, ensuring it is sourced from responsibly managed forests.

Yes, Purpleheart’s durability and aesthetic appeal make it an excellent choice for both residential and commercial projects.

Purpleheart typically starts transitioning from its deep purple hue to a silver-grey within 6 to 12 months of exposure to sunlight and weather conditions. The exact timing can vary based on environmental factors, such as the amount of direct sunlight and exposure to the elements.

Purpleheart transitions from light brown when freshly cut to a deep purple upon exposure, and eventually matures to a silver-grey as it weathers.

Yes, Kwila is known to bleed tannins, especially when it's newly installed or gets wet. This can cause staining on nearby surfaces like concrete or tiles. To manage this, it’s recommended to allow the wood to weather before installation or to use a sealant to reduce tannin bleeding. Regular cleaning and maintenance can also help minimise the impact.

Vitex has minimal tannin bleeding, making it less likely to stain concrete and other surfaces compared to other hardwoods like Kwila.

Kwila is well-suited to New Zealand's climate, offering excellent resistance to decay and weathering, making it a popular choice for outdoor decking.

Regular cleaning and periodic re-coating with a penetrating oil are recommended to maintain the deck's appearance and longevity.

Yes, JSC's Kwila has been a subject of environmental concern due to illegal logging practices in some regions, leading to deforestation and negative impacts on local ecosystems. However, at JSC, we ensure that our Kwila is responsibly sourced and FSC® certified (FSC Licence Code - C003608), meaning it comes from well-managed forests that adhere to strict environmental and social standards. By choosing FSC® certified Kwila, you can enjoy the benefits of this durable hardwood while supporting sustainable forestry practices.

Hardwood decking should be cleaned annually. Use a soft brush with water and mild detergent. Do not direct high pressure water on any part of the hardwood timber. Where a coating is applied, periodic recoating is required to ensure its integrity is sustained. Follow the manufacturer’s instructions regarding hardwood chemical runoff. The amount and characteristics of the runoff will depend on the species, dryness of the boards when installed and how exposed the deck is to the weather.

Yes. After the construction operations are complete, acclimatize the flooring by stacking it in the in-service conditions for a minimum period of two weeks with air circulation to all surfaces as follows:

• Air conditioning operational

• Lighting operational

• Site drainage works are complete

• Space fully enclosed and secure

• Wet work complete and dry

Establish a regular cleaning routine to prevent dirt and debris from scratching the surface of the boards. Use only recommended cleaning solutions and avoid getting water on the floor. Do not use harsh detergents and avoid using any abrasive materials to clean the hardwood flooring.

If coating is to be applied, JSC will always offer this as a Dressed & sanded supply. This is because dressed face timbers close the pores of the timber, meaning coatings sit on the surface rather than absorbing into the fibre, causing delays and potential coating consistency issues. Drying times can also be further reduced by specifying JSC Scumble & Coda coating products. Speak to a JSC representative about the best surface finish and coating options for your specific project.

45+ LRV Paint colour only - no dark colours. Speak to a JSC representative about colour options including stain colours.

Both JSC Scumble® and JSC Coda® Exterior Wood Oils are ideal for timber cladding applications.

JSC Scumble® provides a higher tint coverage while JSC Coda® showcases timber grain with a good penetration into the wood and non-film forming.

The optimal weather conditions are dry weather with a minimum temperature of 13°C. If possible, avoid direct sunlight and high temperatures, so overcast days are ideal.

Do not apply coatings when the substrate moisture content exceeds 18%.

For paint finish:

• all sharp edges must be removed to provide a radius to minimize stress on the paint film

• nails are to be punched and the holes to be primed promptly,

• fill holes with a suitable filler

• filled holes to be primed again and sanded once dry.

For detailed instructions please refer to Cladding Installation and Specification Guide.

Dressed surface: You can use a PAL Speedbrush or a short nap roller.

Band Sawn surface: You can use a wide bristle brush or a medium nap roller.

Another option is to use airless spray equipment (choose a nozzle to deliver a low-pressure coarse spray)

In standard climates and on commonly used kinds of timber species:

· Touch-dry: 3 hours

· Workable: 8 hours

The drying process can be markedly delayed in unfavorable weather conditions (high humidity, low temperatures, minimal air movement). The drying time can also vary depending on the type of wood.

Yes. JSC Coda® Exterior Wood Oil can be used on decking. Coating for decking is only recommended in our clear coating option. 

For spray equipment, brushes, and clothes; clean with hot water. Use a wiping rag with hot water on smooth surfaces and a brush on rough surfaces to clean over-spray or accidental spillage. If brushes remain clogged, rinse with Isopropyl alcohol.

Yes a clear oil can be applied over the initial colour coat of woodoil. We always recommend doing a test sample on an offcut piece of timber where possible to confirm colour is as desired.

Yes, as long as you are using the same base oil i.e JSC Scumble over JSC Scumble or JSC Coda over JSC Coda then a darker coating can be applied. Always check with JSC first to confirm that the colour is suitable for your chosen timber and profile as some timbers can not handle the heat that comes with darker colours. We always recommend doing a test sample on an offcut piece of timber where possible to confirm colour is as desired.

On average, recoating is required every 2 to 4 years, affected by factors such as:

• Weather/UV exposure/Humidity

• Site location and orientation

• Timber species

• Coating colour

• Restricted light and air flow

• Proximity to vegetation and airborne contaminants

• Maintenance frequency

Pencil marks can prove difficult to remove on some coatings, always start with the lightest cleaning method, a light detergent and a stiff brush (like a fingernail brush) and brush in the direction of the grain. Using an eraser may help but can risk making a smooth spot on the board. If this occurs on bandsawn face timbers then a stainless steel wire brush can help to roughen up the texture again before a second coat is applied.

Assuming you have ordered from JSC, one coating would have been applied to the cladding at the factory, prior to delivery. A second coat can be applied 8 hours AFTER installation.

Yes, JSC are happy to provide samples of the species, profile, and even wood oil colours to ensure you get the desired outcome for your build. Send us an email with your request or pop into one of our branches to discuss your requirements!

Yes, JSC has years of experience when it comes to custom and architectural profiles to suit a range of styles and designs. There can be limitations based on things like quantity and weatherproofing considerations so talk to our technical team to discuss options!

For sure. We offer our full range from Cladding, Decking, Panelling, Screens, Battens, Thermally Modified Timber, Flooring and the supporting system fittings for each system for our Waikato & Bay of Plenty customers. Contact us to find out more.

Yes absolutely. Our reps dedicate several days each week to visiting our customers. Simply contact us and we can book that in.

For sure. We offer our full range from Cladding, Decking, Panelling, Screens, Battens, Thermally Modified Timber, Flooring and the supporting system fittings for each system for our Auckland customers. Contact us to find out more.

Yes absolutely. Our reps dedicate several days each week to visiting our customers. Simply contact us and we can book that in.

For sure. We offer our full range from Cladding, Decking, Panelling, Screens, Battens, Thermally Modified Timber, Flooring and the supporting system fittings for each system for our South Island customers. Contact us to find out more.

Yes absolutely. Our reps dedicate several days each week to visiting our customers. Simply contact us and we can book that in.

For sure. We offer our full range from Cladding, Decking, Panelling, Screens, Battens, Thermally Modified Timber, Flooring and the supporting system fittings for each system for our Wellington customers. Contact us to find out more.

Yes absolutely. Our reps dedicate several days each week to visiting our customers. Simply contact us and we can book that in.