In recent years, a new trend in high-rise construction has emerged – the development of skyscrapers constructed largely of wood products (can also referred to as mass timber, cross-laminate timber, and/or engineered-wood).
Use of these natural materials have the benefits of a reduced carbon footprint (15-20% lower than steel), lighter weight (approximately 1/5 that of concrete), quicker construction times (25% faster), prefabrication, and being a renewable resource.
The list below identifies those skyscrapers (completed or under construction) which are primarily built of timber and =/+ 100 feet in height.
- Ascent (Milwaukee, Wisconsin: preliminary site work underway) = 283 feet (as revised in March 2020)/25 stories
2. Mjøstårnet Tower (Brumunddal, Norway: 2019) = 280 feet/18 stories
3. HoHo Tower (Vienna, Austria: 2020) = 276 feet/24 stories
4. Terrace House (Vancouver, British Columbia: under construction) = 232 feet/19 stories
5. Sara Cultural Centre (Skellefteå, Sweden: under construction) = 226 feet/20 stories
6. Brock Commons Tallwood House (Vancouver, British Columbia: 2017) 174 feet/18 stories (hybrid timber tower with a steel and concrete core)
7. Treet (Bergen, Norway: 2015) = 173 feet/14 stories
8. Light House (Joensuu, Finland: 2019) = 157 feet/14 stories
9. Sensation (Strasbourg, France: 2019) = 125 feet/11 stories
10. SKAIO (Heilbronn, Germany: 2019) = 112 feet/10 stories
11. Forte (Melbourne, Australia: 2012) = 105 feet/10 stories
UPDATE – Proud Kanda Surugadai (Tokyo, Japan: under construction – to be completed 2021) = Unknown height/14 stories
A number of other timber high-rises have been proposed worldwide. But, because projects are often proposed without actually being built, the list above only includes those that have been completed or are underway.
One may wonder about possible dangers of tall buildings constructed of wood, particularly fire. In some instances this has been addressed by constructing a concrete and/or steel core surrounded by mass timber or cross-laminated timber construction. Secondly, studies have shown that charred mass timber/cross-laminate timber remains very strong. In fact,
“The unburnt wood, protected by the charred wood, retains up to 100 percent of its initial strength.”
Source: Fire Performance, reThink Wood
Furthermore, studies show:
“During a fire resistance test of a 5-ply cross-laminated timber (CLT) panel wall, the panel was subjected to temperatures exceeding 1,800 Fahrenheit and lasted 3 hours and 6 minutes, far more than the two-hour rating that building codes require.”
As more information becomes available, building codes, particularly here in the United States, will need to be modified to allow taller mass timber structures that the current limit(s). When completed, Ascent in Milwaukee will greatly supersede the current tallest mass timber tower in the United States, Carbon 12, an 85 foot tall apartment building in Portland, Oregon (see image below).