Yesterday, as night was nearly falling, I was returning on my bicycle and passed by a house under construction (photo 1). It was barely visible in the darkness, but my phone managed to capture it. Almost all of our buildings under 5 floors are of this frame type. The frame is made of wood, and the walls are usually made of OSB boards, and less frequently of CLT boards.
An OSB board is made of chips/flakes bonded with resins and compressed under pressure and heat. The chips are layered so that the top and bottom layers run along the board, while the middle layer runs across. It’s cheaper than plywood. The foundation of the building is always concrete. The elevator shaft is also made of concrete. Later, the exterior walls will be covered with finishing materials for the facade—siding and/or brick, and the interior will be lined with drywall. In terms of fire resistance, it’s all up to standard—drywall can withstand flames for a minimum of one hour, enough time for the fire services to not only arrive but definitely extinguish the fire.
Despite the apparent vulnerability of wood to fire, treated wooden supports can also be safer in the event of a fire than it seems. Their greater thickness (plus impregnation) allows them to burn slowly and evenly, and they can remain standing even during severe fires, unlike steel supports, which can deform and collapse at high temperatures.
There are also wooden poles along the road. Nowadays, cables are increasingly laid underground, but where supports are needed (up to 10kV), they are often wooden.
The cost of a wooden pole is less than that of a similar item made from concrete or steel. Wooden poles are lighter, meaning they’re easier to transport, and naturally, easier to install on-site. A standard timber truck can transport about 40-50 tree trunks, while the number drops by half with concrete piles. A wooden support has a certain flexibility, which is a major advantage in regions with strong winds. If a line is made of such supports and one pole is damaged, it won’t pull the others down with it, creating a “domino effect”. Moreover, mounting something on a wooden support is simpler than on a concrete or steel one.
The lifespan of a wooden support ranges from 40 to 80 years. To ensure its durability, it is treated in dryers, submerged in a special pressure chamber where air is evacuated and a solution containing chromium, copper, and arsenic (CCA — chromated copper arsenate) is injected, and because the substances are absorbed deep into the wood up to 9 centimeters, it’s no longer quite the same wood 🙂 In contrast, the lifespan of iron-concrete supports ranges from 35 to 50 years.
Moreover, in the event of disasters or accidents, it is easier to remove a support from the road. Simply by sawing it into pieces with a manual chainsaw. Which, for obvious reasons, is not as feasible with a support made from metal or iron-concrete.
Such are the advantages of what seems like a quite archaic item as a wooden utility pole. Apparently, the engineers in the states are quite conservative, for whom all the aforementioned benefits are far more important than appearance.
Hi, I'm Rauf Aliev. 