We are a full-service construction company located in San Francisco. We do mostly residential and some commercial projects. We have been doing this for many years. We do everything from foundation repair and replacement to entire house remodels. Because of the complexity and variation of building styles and topography, remodeling and retrofitting in San Francisco requires a broad knowledge base. We have that knowledge base.
The most common issue is deterioration. Most of the homes we encounter were built between the late 1800s and mid 1900s. They didn't have the construction protocols and materials we have today. People will have either brick or concrete foundations. The brick foundations, by their very nature are substandard. They are only as strong as the bond provided by the mortar joint. For simply carrying the load of a house, a properly constructed brick foundation is fine. One problem is we live in earthquake country. Once the ground starts moving, all bets are off.
The other issue is the mortar joints begin to deteriorate, which compromises the bond between each brick. Many areas of San Francisco are built on sand. Many years ago, contractors would simply use beach sand for their mortar mixes. Using beach sand dramatically reduces the lifespan of the foundation. This actually is one of the reasons the older concrete foundations fail as well. We see many concrete foundations that were built using substandard sand and they are crumbling apart.
One of the few practical repairs is underpinning. We typically underpin foundations when the load exceeds the ability of the foundation to carry it. The signs that your foundation may need underpinning are cracking of the foundation and settling.
The other repairs are capping and sistering. Capping your foundation is good when your existing mudsill is at or below grade. The mudsill is the horizontal framing member which sits on top of the foundation. The cap raises the sill height above the grade which prevents moisture from touching the framing of your building.
I almost never recommend sistering a foundation. "Sistering" a foundation is basically pouring a new foundation wall against the existing foundation wall. I don't recommend sistering because it creates a very bulky foundation. If your existing foundation is bad enough to warrant sistering, I usually consider it a good candidate for replacement.
I often see foundations that are deteriorating a bit, but there are no visible signs of cracking. If it looks rather solid, I usually recommend leaving the foundation alone and concentrate on making sure the anchor bolts and sheer are up to code.
Once it is determined that your foundation needs to be replaced, you need to hire an engineer or a company like mine to prepare the structural drawings. I work with several engineers. If you have any as-built plans, this can save you a little bit of money. As-built plans are plans of your building and lot that show what is currently there. Once the plans and calculations are developed, they are submitted to your local building department and a permit is pulled for the project. If you are working with an engineer, you can put your plans out to bid. If you are working with a contractor, you are ready to go.
The basic process for foundation replacement is as follows: First we need to shore the building. This is the temporary support of your building. This is what takes the weight off of your foundation which allows us to do our work. Next we break out the existing foundation and excavate for the new one. Then we install the forms and rebar for the new foundation. Install new mudsills, anchor bolts and necessary rods. Pour the concrete. Remove the forms. Tighten the bolts and do finish work.
Quite often there is more work involved because the foundation replacement is done in conjunction with bringing the ground floor up to code. Expect there to be other items such as mechanical connectors and sheer walls that will need to be dealt with.
I would say one of the biggest challenges is determining what really needs to be done. Then, actually getting the finances together and doing the work. Foundation work isn't like having your kitchen remodeled. People have a tough time spending $50,000 - $150,000 on an item that doesn't improve the aesthetics of their building. Well, unless you consider how it might look after an earthquake!
Advantages - It increases the value of your property. It increases the safety of the people inside the home. It helps maintain the value of your property after an earthquake. It increases the lifespan of your home. A good foundation limits settlement which means less cracks throughout the house.
Disadvantages - It costs money, but can potentially save you lots of money and headache in the future. Also, your home becomes a construction zone during the replacement process. It's never fun having workers banging nails at 8:00 in the morning.
Many people ask if they need to move out during the work. Typically no, but expect occasional disruption in some services. We will let them know ahead of time if anything needs to be shut off.