Room Additions: A Hidden Danger
You might retrofit your house by precisely following the various retrofit guidelines, including the most recent one FEMA P-1100 and your house will be just as exposed to damage as it was before you did anything at all. This webpage will help you make sure this does not happen to you. Many older homes have additions which can seriously compromise a retrofit if not dealt with properly.
It is not uncommon for an older home (such as the 1955 house I live in) to have originally been 900- 1200 square feet. Over time demand for larger homes increased considerably. Many homeowners built additions on the back of their houses (such as the house I live in).
The building code does not tell a contractor how to connect an addition to the main house. Contractors do no consider future earthquake forces.
The Removal of Existing Cripple Wall Bracing
What To Do About It
Sometimes the addition is attached to the floor in such a way that you can’t attach a shear wall to the addition. Contractors usually leave the stucco on the cripple wall. There is no one size fits all solution to this. Frankly, you simply need to know what you are doing. These situations usually involve a lot of problem solving.
That being said, lag screws, machine screws, and nails are the most common types of connectors. Assuming the two floors are butted up to each other, Simpson SDS Heavy Duty Connectors often do the trick. Be sure the screws go all the way though both floor joists or blocking when you screw them together. They come in 4 1/2″ to 8″ lengths. Sometimes custom made floor to floor connectors must be designed on site using allthread. As far as the quantities go, just put in a whole bunch. That is a lot cheaper than paying someone to figure out how many you need.
Floor to Floor Connectors
Separation can also occur when the main addition rotates away from the addition. To the right is one solution using horizontal hold downs.