No two homes are built the same way. Each home was built during a unique time and by unique builders. Because of this, they cannot all be seismically retrofitted in the same manner. Practicality and knowledge must be applied, accordingly.
Initially, we will inspect your crawl space area (which is likely the most vulnerable part of your home).
Next, we will give you a customized plan to address your structure's needs.
Other issues that we look for include:
#1: Water Drainage Issues (From roof water, surface water, and subterranean water).
#2: Foundation Issues: We look for cracks, upheaval, settling, over-turning, and earth-to-wood contact.
#3: Framing/Structural Issues: We evaluate the centerline beams, centerline posts, the floor joists (whether they are singular or bypassing), the top plates of your cripple walls and the redwood or pressure-treated sill plate on your foundation.
#4: Dry Rot / Termite Issues: Although this is not our main reason to visit, we will mention if there are any noticeable signs of termite damage or dry rot present.
On average, the Hayward Fault lets go/slips every 140 years. This statistical average was due in 2008. We are now more than 17 years overdue for the big one, which is why we believe it is important to prepare now for the inevitable.
Do recently built homes still need to be seismically retrofitted?
There are a lot of different variables to consider, but most houses that were built before 1960 will be most vulnerable to damage from a major earthquake, as plywood and bolts were not widely used before that time. Even with the usage of plywood and bolts, vulnerabilities within structures can still be present. Homes that were seismically retrofitted after the year 2000 often times are missing their wall to floor bracket attachments, making it so the walls are properly attached to the concrete foundation, but the floor system still has a potential of separating from the wall systems.
What is the most common cause for foundation settling/over-turning?
The most common cause of foundation settling/over-turning is due to differential moisture content from the outside of foundation to the inside of the crawl space, as the crawl space will typically stay dry with the outside soil becoming super-saturated from rain, irrigation, etc. Over time, the weight of the foundation has an easier time compressing the wet,soft soil more readily than the dry,hard soil within the crawl space. Once the foundation starts to over-turn the process becomes inversely worse as the foundation becomes more and more imbalanced.
How exactly does water drainage work and what is the importance?
French drains, which are used to channel unwanted water away from the house, are implemented with deep trenches within the soil surrounding your structure. The trenches are lined with fabric to filter the dirt from the water (which will prevent the system from becoming clogged over the years. We then place a perforated pipe in the bottom of the trench with the holes facing down and toward the sides (having the holes face up towards the sky is a common misinstallation). Next a filtration sock will be placed around the perforated pipe for added protection from silt. Then, the entire trench will be filled with 3/4" gravel. Because these rocks are jagged and uneven, gaps will be present which will allow water to flow between the rocks and down towards the perforated pipe. Once the water reaches the perforated pipe, it will be free to flow away from the house. If the bottom of the trench is lower than the top of the street then you will need a sump pump pit to lift the water up and out to the street.
