Timber in construction is one of the oldest and most versatile building materials. Used for centuries for everything from houses to bridges, it offers a unique combination of strength, workability, and aesthetics. From framing entire structures to adding decorative elements, timber continues to be a popular choice for builders today due to its many advantages. Having said this, it is important to know the main important aspects of wood that require extra attention during the design and construction process.  

In this blog, we will discuss three very important aspects that need to be taken into consideration when dealing with timber in construction. Furthermore we will advise to add extra protection to enhance the timbers durability. 

Need-to-know Characteristics of timber in construction.

By understanding the “NEED-TO-KNOW” aspects, you can create stunning, functional, and durable timber structures that overcome common concerns and leverage the inherent advantages of wood. The following aspects are important to keep in mind: 

Water and Moisture is the enemy of wood 

Stagnant water creates the perfect environment for biological agents that break down wood. The key to designing with timber is to prevent water from becoming trapped.  

Even small amounts of trapped moisture can lead to rot, mould, and structural issues. Let’s break it down: 

Roof: The Guardian Against the Elements 

Flashing Fundamentals:

Flashing plays a starring role. Think of it as a hidden suit of armour for your roof. Properly installed flashing around chimneys, vents, skylights, and roof valleys (where two sloping sections meet) creates watertight seals. Water following these channels is directed away from the timber structure below. Different flashing types are used depending on the specific application (e.g., valley flashing for roof dips, and step flashing for chimneys). 

Drainage Champions: Gutters and Downspouts:

Even with flashing, some water will make contact with the roof. A well-designed drainage system ensures this water is swiftly directed away from the building. Seamless gutters collect water, and properly sized-downspouts channel it away from the foundation. Remember, improperly placed downspouts can direct water toward the timber framing, so their positioning is critical. 

Slope Matters:

The roof pitch should be sufficient to shed water effectively. Steeper pitches encourage faster water runoff, minimizing the time it spends in contact with the roof surface. However, local building codes and aesthetic considerations also play a role in determining the optimal roof pitch. 

Windows and Doors: Keeping the Wet Stuff Out 

Flashing Friends Again: Flashing also plays a crucial role around window and door openings. It’s meticulously installed around these perimeters to channel water away from the timber framing. Think of it as a hidden moat, directing water away from the castle walls (your timber structure) and towards the moat’s edge (the building’s exterior). 

Weatherproofing Warriors:

High-quality windows and doors with proper weatherstripping are essential. Weatherstripping creates a tight seal between the window/door frame and the building envelope, preventing water infiltration. 

Overhangs for Added Protection:

Strategically placed overhangs above windows and doors provide an extra layer of defense. They act like umbrellas, shielding these openings from wind-driven rain and preventing water from directly hitting the timber components. 

Foundation: The Bridge Between Structure and Ground 

Waterproofing the Base:

The foundation is the bridge between the timber structure and the ground. Proper waterproofing of the foundation walls is vital to prevent moisture from wicking up into the timber elements. A waterproof membrane acts as a barrier, keeping the ground’s moisture at bay. 

Drainage Done Right:

A well-designed drainage system around the foundation perimeter is crucial. This system channels water away from the building, preventing it from accumulating around the foundation and potentially seeping into the timber framing. French drains or gravel channels can be effective solutions. 

Crawlspace Considerations:

If your timber structure has a crawlspace, adequate ventilation is essential. This prevents moisture from accumulating and creates a damp environment conducive to rot and mould growth. Proper ventilation allows moisture to escape and helps maintain a healthy environment for the timber structure. 

Banishing Horizontal Hold-Ups 

Sloped Surfaces for Speedy Drainage: Horizontal surfaces like decks and balconies are prime locations for water to pool. When designing these elements, incorporate a slight slope to encourage water to drain properly. Imagine a tilted stage – water naturally flows downhill and away from the building. 

Drainage Channels as Allies:

Don’t rely solely on the slope. Incorporating drainage channels within the deck or balcony construction further enhances water flow. These channels collect and direct water towards designated drainage outlets, preventing it from accumulating and potentially causing problems for the timber structure below. 

Weathering the Storm 

South Africa’s climate can be tough on wood. The combination of heat, dew, frost, and fluctuating humidity accelerates weathering compared to more moderate climates. Here’s how to design for longevity: 

Sound Decisions: Acoustics and Insulation 

Timber structures can sometimes struggle with soundproofing. However, there are numerous design solutions available to achieve excellent acoustic performance on both walls and floors. A separate discussion on these techniques is beyond the scope of this blog post, but it’s important to acknowledge that good soundproofing is achievable in timber buildings. 

On the flip side, thermal insulation is a major advantage of timber. Wood is a naturally poor conductor of heat, offering roughly 400 times the resistance of steel and 10 times that of concrete (per unit volume). However, poorly designed and constructed walls can negate this benefit. Here’s how to maximize thermal insulation: 

The Power of the Wall System:

The design and construction of the wall system, including the type and thickness of insulation used, plays a critical role in achieving optimal thermal performance. 

Timber Done Right: A Winning Proposition 

By understanding the unique characteristics of wood and incorporating best practices into the design, timber structures can outperform buildings constructed with other materials in all the areas discussed above. Unfortunately, not all designers and contractors are equally familiar with these nuances. 

The good news is that South Africa has a comprehensive timber frame standard, SANS 10082. Following the design criteria outlined in this standard helps avoid the pitfalls associated with poorly designed timber structures. Specifying high-quality, structurally graded timber is also crucial. 

When it comes to building strong and reliable structures, the quality of your materials matters. That’s why we’re proud to offer SABS-approved H3 CCA pressure-treated and untreated construction timber. This certification ensures that our timber meets the rigorous standards set by the South African Bureau of Standards (SABS). 

Specifically, our timber falls under the S5 Construction grade. This means it’s been thoroughly tested and proven to possess the strength and durability needed for a wide range of building projects, from small renovations to large-scale construction. Whether you’re building a new home, adding an extension, or tackling another project, you can be confident that our SABS-approved S5 construction timber will provide the reliable foundation you need. We have a wide range of Construction timber sizes available, to download our pricelist, please click on the following link:  Construction Timber

Adding a little extra to your timber structure

Both untreated and graded CCA-treated timber are suitable for construction projects, with pine being a popular choice. However, as a softwood, pine is more susceptible to insect damage, rot, and harsh weather. CCA treatment significantly enhances durability, but additional protection can further extend the lifespan of your project. 

We offer a high-quality sealer ‘Timberlife’ that’s fully compatible with CCA-treated wood. This exceptional product can be applied to all our poles and timber and comes in a clear finish or a variety of attractive tints. Please click on the following link to learn more: Timberlife Sealers