Wood is used across almost every part of building and DIY — roof trusses, ceilings, floors, decking, cupboards, doors, window frames, furniture and formwork. Which wood suits which job depends on strength, durability, moisture exposure and, in South Africa, resistance to termites and borer.
What is Wood?
Wood is the structural tissue of trees, made largely of cellulose fibres bound in lignin. That fibre alignment is why wood is far stronger along the grain than across it — the single most important thing to understand when using it.
In building, “wood” almost always means one of these:
| Type | Examples | Typical use |
|---|---|---|
| Softwood | SA pine, saligna | Structural framing, roof trusses, general construction |
| Hardwood | Meranti, oak, kiaat, balau | Doors, windows, furniture, decking |
| Engineered boards | Plywood, MDF, chipboard, OSB | Sheeting, cupboards, shopfitting |
| Treated timber | CCA-treated pine | Outdoor, ground contact, structural |
“Softwood” and “hardwood” describe the tree, not the wood’s hardness — they refer to conifers versus broadleaf trees. Balsa is a hardwood; yellowwood is soft to work. In practice, though, most hardwoods are denser and more durable.
Two things determine whether wood lasts in South African conditions, and both are frequently underestimated:
- Moisture. Wood is hygroscopic — it absorbs and releases water, swelling and shrinking as it does. Wood that gets wet and cannot dry will rot. Design that lets water drain and timber breathe matters more than any coating.
- Insects. Termites and powderpost borer are a genuine problem across much of South Africa. Untreated softwood in ground contact or in a poorly ventilated roof space is vulnerable, which is why treatment classes exist.
SANS treatment classes (H2 to H6) indicate what exposure a treated timber is rated for — H2 for indoor dry, H3 for outdoor above ground, H4 for ground contact, H5 for fresh water contact. Matching the class to the application is the single most useful decision when buying structural or outdoor timber.
What is Wood used for in building or DIY?
- Roof structures — trusses, purlins, battens and rafters, usually treated SA pine.
- Ceilings, using boards, panelling or as a substrate.
- Flooring, both solid timber and engineered.
- Decking, using treated pine, balau or composite alternatives.
- Cupboards and built-in furniture, typically melamine-faced board, MDF or plywood.
- Doors and door frames.
- Window frames, usually meranti or treated pine.
- Skirtings, cornices and architraves.
- Formwork and shuttering for concrete.
- Fencing, pergolas, carports and outdoor structures.
- Furniture making and joinery.
- Stud walls and drywall framing.
- Musical instruments, where specific species are chosen for tone.
Wood is unusual among building materials in being both structural and decorative, which is why it appears at every stage — from the trusses nobody sees to the finish everybody does.
Common applications for Wood
Roofing. SA pine trusses are the standard for pitched roofs, engineer-designed and factory-made for anything beyond a simple span. Use timber treated to the correct SANS class — an untreated truss in a warm roof space is exactly what borer and termites look for.
Ceilings. Timber boards, tongue-and-groove panelling or plywood are used both structurally and decoratively. Allow for movement — timber ceilings that are fitted tight will buckle as humidity changes.
Cupboards. Melamine-faced chipboard is the workhorse for carcasses; MDF takes paint well for doors; plywood is used where strength or moisture resistance matters. Chipboard and standard MDF fail badly if they get wet, which is why they are poor choices under a sink without moisture-resistant grades.
Decking. Balau and other dense hardwoods last well outdoors; treated pine is cheaper and needs H3 or higher. Leave drainage gaps, ventilate underneath, and re-oil annually — decking fails from trapped moisture far more often than from wear.
Doors and windows. Meranti is the common choice, being stable and workable. Seal all six faces, including the top and bottom edges — unsealed end grain absorbs water rapidly and is the usual place rot begins.
Where Wood fits in a typical project
- Structure first — trusses, floor joists, stud framing. Engineered, treated, and inspected before anything is closed up.
- Then the envelope — window and door frames, fascias and barge boards.
- Then internal linings — ceilings, flooring substrate.
- Then joinery and finishes — cupboards, skirtings, doors, trim.
- Finally protection — sealing, oiling or painting, and ongoing maintenance.
Timber should be allowed to acclimatise to the space before fitting, particularly flooring. Wood delivered from a dry warehouse into a humid coastal house will move — fitting it immediately is why floors cup and gaps open up.
Choosing, handling and compatibility considerations
- Match the treatment class to the exposure. H2 indoors, H3 outdoors above ground, H4 in ground contact.
- Check for straightness, splits and large knots before buying — sight along the length.
- Store timber flat, off the ground and under cover. Timber stored leaning against a wall will bow.
- Use the right fasteners. CCA-treated timber corrodes ordinary steel — use hot-dip galvanised or stainless steel, particularly near the coast. Mismatched fasteners are a common cause of premature failure.
- Seal cut ends of treated timber. Cutting exposes untreated wood, and end grain is where water enters.
- Allow for movement. Timber expands and contracts across the grain — leave expansion gaps in flooring and panelling.
- Wear a mask when cutting MDF and chipboard, and when sanding treated timber. The dust is a genuine respiratory hazard, and hardwood dust is a recognised carcinogen.
- Do not burn treated timber, or use its offcuts for braai wood — CCA-treated wood releases toxic arsenic compounds when burned.
- Check for borer holes in second-hand or reclaimed timber before bringing it into a building.
Related construction material guides
Frequently asked questions
What is wood used for in building? Roof trusses, ceilings, floors, decking, cupboards, doors, window frames, stud walls, formwork and furniture — both structural and decorative work.
What wood is used for roofing? Treated SA pine is standard for trusses, purlins and battens in South Africa. Use timber treated to the correct SANS class, as untreated pine is vulnerable to borer and termites.
What wood is used for decking? Balau and other dense hardwoods, or treated pine at H3 or above. Ventilation underneath and drainage gaps matter more than the species for how long it lasts.
What wood is used for cupboards? Melamine-faced chipboard for carcasses, MDF for painted doors, plywood where strength or moisture resistance matters.
What wood is used for ceilings? Timber boards, tongue-and-groove panelling or plywood. Allow for movement — ceilings fitted tight will buckle as humidity changes.
Does hardwood mean hard wood? No. Hardwood and softwood refer to broadleaf versus coniferous trees. Balsa is technically a hardwood.
Can I burn treated timber offcuts? No. CCA-treated wood releases toxic arsenic compounds when burned. Dispose of offcuts, never use them as braai wood.
Why does my timber floor have gaps? Usually because it was not allowed to acclimatise before fitting, or expansion gaps were not left. Wood moves with humidity, and that has to be designed for.