Maintenance guide for char-surface cladding products

This guide applies to: Hiili Korppi

About maintenance in general

Charred wood is generally easy to care for and requires less upkeep than wood that has been only oiled. With proper care and correct maintenance, charred wood remains beautiful for decades.

This guide describes the maintenance of Carbon and Raven cladding products made from pine and spruce, in the use cases they are suited to.

Read the section that applies to your use case as well as the common finish section.

Maintenance: exterior cladding

Avoid mechanical strain. A char surface does not tolerate hard abrasion or impacts.

Keep the cladding surface clean. When needed, rinse or gently wipe off leaves, pollen, cobwebs and other dirt. If you rinse the surface, use as little water as possible and make sure water does not get into the structures behind the cladding.

Prevent build-up of organic matter. Make sure that shrubs, grass or tree branches do not collect against the façade.

Wash carefully if necessary. If the surface needs washing, use a mild, pH-neutral detergent. Avoid excessive scrubbing and harsh detergents which can damage the surface. Test the detergent on a small area first.

Mind the structures. Ensure that eaves, trims and flashings direct water away from the façade.

Inspect the cladding regularly and re-oil where needed.

Need for re-treatment

The char surface protects the wood from the sun’s UV radiation, and char-surface exterior cladding does not grey in the same way as wood that has only been oiled. The linseed oil applied at the factory binds the char to the surface so that it does not dust or flake off under light contact.

Outdoors, the protection provided by the oil weakens gradually. How quickly depends on how much sun, rain and snow the surface receives. For this reason we do not give a fixed maintenance interval; instead, we recommend inspecting the façade regularly, especially south- and west-facing walls and areas not sheltered by the eaves.

Maintenance treatment with oil may be due if:

a significant amount of char comes off on your hand when you touch the surface lightly (small particles are not a problem)
the char surface has sustained a substantial area of damage

In that case, treat the affected areas as described in “Maintenance treatment”. If in doubt, please contact us.

Maintenance: interior cladding, sauna and wet rooms

Avoid mechanical strain. A char surface does not tolerate hard abrasion or impacts.

Dust lightly. Use a soft duster, microfibre cloth or lightly damp cloth. Do not use abrasive cloths or strong detergents.

Prevent standing water. The structure must be able to dry out. Interior cladding rarely needs wiping with a damp cloth.

Wood surfaces in sauna and wet rooms. Charred surfaces also suit saunas and wet rooms. Even in these spaces, surfaces should be dried after use and good ventilation maintained. Avoid heavy scrubbing when cleaning. If you use cleaning products, choose ones with as neutral a pH as possible.

Prevent stains from setting. If anything is spilled on the surface, wipe it off carefully and immediately.

Re-treatment of interior cladding

Hiil products used as interior cladding do not structurally require re-treatment with oil.

Maintenance treatment

Use the same finish product that the factory originally applied. Hiil products are treated with special linseed oil. The oil shade depends on the surface — order maintenance oil using the product’s surface name. If you are uncertain, ask us for a suitable finish and more detailed instructions.

Always follow the instructions of the finish product. Test the maintenance treatment on a small area in an inconspicuous spot before treating the visible surfaces more widely. Wipe off any excess finish that the surface has not absorbed.

Protect sensitive surfaces from possible oil splashes and drips (paving, floors, plinths, windows, etc.).

Note that in direct sunlight or on a hot day, oils can dry too quickly. The oil then does not have time to soak into the product adequately, and proper protection does not form.

WARNING — risk of spontaneous combustion

WARNING! Many drying natural oils pose a risk of spontaneous combustion.

Rags, sponges and sawdust soaked in oil can ignite spontaneously if left in a pile.

Lay rags and sponges flat to dry one by one outdoors on a hard surface, or submerge them in water — never leave them bundled in a bin.

Repairing a damaged char surface

If damage occurs that breaks the factory-treated surface and exposes fresh, untreated wood, DO NOT repair the damage with a gas torch. Finish products generally do not tolerate fire and may ignite or smoulder.

On char-surface products (Carbon, Raven), the damaged area can be re-treated with the same linseed oil used on the product, or with the black linseed oil supplied for cut ends.

Re-treatment does not restore the broken char surface, nor does it tint the wood exposed under the char to the same shade. Instead, it protects the exposed wood with oil.

We do not recommend black paint for repairs, since its sheen and colour differ from the charred surface in the repaired spots.

If the damaged area is large, repairing the char surface may be impossible. In that case we recommend replacing the damaged panel or product entirely with a matching new one.

Tips for successful surface treatment

Check conditions. Temperature +10…+25 °C and low direct sun are ideal. In too high temperatures the oil dries too quickly and does not absorb properly.
Use the original finish product. Re-treat with the same product that the surface was originally treated with (black oil is also suitable).
Protect surroundings from possible splashes — paving, floors, plinths, windows.
Test first on a small, inconspicuous area to confirm the result.
Apply a thin, even coat and let the oil absorb. Wipe off any excess that the surface has not absorbed.

Re-use and disposal

All Hiil products are designed for long-term use lasting decades. If the products are dismantled for any reason, reuse the timber elsewhere if possible. This way the carbon bound in the product stays bound, the work that went into manufacturing remains useful, and the wood gets a new life.

All Hiil products contain only wood, linseed oil, and possibly a small amount of colour pigment. The finishes used in the products are not classified as hazardous. If you choose to dispose of the product, the timber can be used as an energy source.

Contact

Hiil Oy
info@hiil.fi
https://hiil.fi

Up-to-date contact information is available at hiil.fi.