Timber framed houses are considered to be weak and can easily be damaged on the onset of an earthquake or any other natural catastrophe. To prevent such scenarios one is advised to put into place structural modifications to strengthen the wooden frame.
When building a house from scratch, a lot has to be considered especially the type of wood to be used so as to ensure that the structure is strong and stable. Lightweight framing should be avoided. The wood used should be allowed to dry so as not to lose shape during its drying process. The foundation is the next section to consider since the whole structure lies on it. It should be reinforced with steel bars so that it can be strong enough. The sill plate is typically anchored to the foundation or slab of concrete, depending on the application. The sill plate must be anchored to the foundation to ensure proper construction and safety. After it is well bolted then, the wooden frame is to be attached to it.
Large unreinforced opening in wooden framed structures are the next key potential areas which should be strengthened. The openings include halls, garages, balconies, and stairs. The pillars used in the construction of these openings are the ones to be reinforced. A steel reinforcement is advised for balconies in the upper stairs rooms. For pillars on the ground floor, they are supposed to be attached to the foundation and also reinforced using hardened steel metals; this is because they support the whole building.
A seismic survey is conducted on an already built structure so as to identify potential problems in the structure. Such problems may include; joints which were not well fastened or deformed wooden parts which dried off unevenly and lost its shape. Such problems should be addressed immediately, or it may end up causing a fatal damage at the end. In such a situation joints are fastened and the deformed sections removed and reinstalled with stronger material.
How to strengthen timber framed houses
Timber framed housing has performed extremely well here in Christchurch, New Zealand during the Canterbury Earthquakes in 2010. We design these homes to handle seismic loads and the solutions usually consist of braced wall panels from plasterboard, plywood or steel frames. The main area for attention is the connection to the roof and floor structure to ensure that the entire building works together to distribute loads to as many wall elements as possible.
Agree with you willem. Unreinforced masonry poses a significant hazard in seismically active areas. The City of Portland, sitting astride a major fault line, has over 1,200 unreinforced masonry structures dating back to the mid 19th century. Retrofitting many of these with internal shear walls using timber technologies such as CLT would avoid the costly "corsets and girdles" of steel that are usually employed for this purpose. The epoxy coating that the all-brick and timber frame Ghiradelli Square in San Francisco employed is also a technique well worth looking into for walls and facades that need more than an internal shear wall structure.
I believe the opening statement of this article is extremely incorrect and cast an unfair opinion on timber framed construction. Like the answer from Roy Hamilton above we have been designing timber framed houses for many years that have withstood severe seismic shocks. Here in New Zealand we have just experienced another spate of good shock in several areas around the country. Most of the damaged buildings are concrete and masonry construction....not the timber structures.
Cross Laminated Timber shear walls and floor diaphragms replacing stick framing can make a huge difference to the safety of timber framed buildings (and unreinforced masonry buildings) during earthquakes. The 4.125" thick 3-Ply panels manufactured by D.R. Johnson in Riddle, OR, for example, make perfect shear walls. These panels are unobtrusive, can be drywall finished and to the casual eye few people would notice they are there especially if they simply replace a questionable stick-framed shear wall. Flooring would need 5 or 7 ply panels depending on the live loads and span conditions.
Several significant shake table tests have shown that CLT shear walls and floor diaphragms can withstand seismic events that would cause the average stick frame building to collapse into the first floor.
snore