What Demolition Often Reveals in Older Marin and San Francisco Homes

Written by Home Team Services on September 2, 2026. Posted in Uncategorized.

If your home was built before the 1960s, and a lot of Marin and San Francisco housing stock was, there’s a good chance that once demolition starts, your contractor is going to find something you didn’t plan for. That’s not a sign of a bad house or a bad contractor. It’s simply what happens when walls that have been closed for 60, 80, or 100 years finally get opened.

The problem isn’t that these findings happen. It’s that most homeowners go into a remodel without knowing what categories of surprises are common, which ones require a decision on the spot, and which ones can be planned around in advance. Knowing that ahead of time changes how you budget, how you schedule, and how much stress the project actually causes.

Here’s what tends to show up, and how to think about each one.

Framing That Doesn’t Match the Plans

Older homes were often built without formal engineered plans, or with plans that were modified during construction and never updated on paper. Once framing is exposed, it’s common to find:

Ceiling joists or floor framing that’s undersized by current standards
Load paths that don’t match what the original drawings (if any exist) suggest
Notched or drilled framing members from decades of prior plumbing or electrical work, sometimes cut deeper than they should have been

None of this means the house is unsafe to live in as-is. It does mean that a wall you assumed was purely cosmetic might be doing structural work, or a beam you planned to remove might need a larger replacement than budgeted. This is one of the findings that most often needs a decision before work continues, since framing changes affect sequencing for everything that follows.

Electrical Systems From a Different Era

Homes built before the 1960s frequently still have some original wiring, even after partial updates over the years. Common finds include:

Knob-and-tube wiring, which isn’t inherently dangerous when intact and undisturbed, but often can’t be safely extended or buried in insulation
Ungrounded circuits feeding rooms that now need to support modern appliance loads
A main panel with less capacity than a remodeled kitchen, an added bathroom, or a future EV charger will need

Electrical findings are usually addressable, but they affect the order of operations. If a panel upgrade turns out to be necessary, that’s a decision worth making early, since it affects permitting and can affect timing for the rest of the electrical rough-in.

Plumbing Behind the Walls

Marin and San Francisco homes from this era commonly used galvanized steel supply lines and cast iron drain lines. By the time a wall opens, it’s common to find:

Galvanized pipe with significant internal corrosion, which restricts water flow even if there’s no visible leak yet
Cast iron drain lines with buildup or early-stage failure at joints
Old shutoff valves that no longer fully close

A pinhole leak or a valve that won’t shut isn’t a crisis, but it’s exactly the kind of thing that’s far cheaper to address while a wall is already open than to discover later as an emergency repair. This is a good example of a decision that’s easier to make in the moment, once your contractor can actually see the condition of the line, than to try to plan for months in advance.

Insulation and Moisture Conditions

Many older Bay Area homes were built with little or no wall insulation, and moisture management wasn’t handled the way it is today. When walls open, it’s common to find no vapor barrier at all, or one installed incorrectly for the home’s specific exposure. We’ve written separately about how moisture management and vapor barriers should be handled in a Bay Area remodel, and older homes are exactly where this matters most, since the original construction usually didn’t address it at all.

Lead Paint and Other Materials Worth Testing

If your home was built before 1978, painted surfaces may contain lead, and federal rules govern how contractors are required to handle that during renovation work. This isn’t something to guess about. The EPA’s Renovation, Repair and Painting Rule explains what’s required when painted surfaces are disturbed in pre-1978 housing, and a licensed contractor should be following lead-safe work practices as a matter of course on any home from that era. Depending on the scope of work, testing for lead paint or other materials before demolition begins is worth discussing with your contractor as part of early planning, not something to find out about after the fact.

Foundation Conditions, Especially on Marin’s Hillsides

Many older Marin homes, particularly those built on sloped or hillside lots, were constructed on raised foundations with cripple walls, short wood-framed walls that connect the foundation to the first floor. These are a known seismic vulnerability point in older construction, and it’s common for a remodel, especially one involving structural work, to reveal that cripple walls were never braced or that the foundation connection is minimal. San Francisco’s older flat-lot Victorians and Edwardians have their own version of this issue, often involving perimeter foundations that were adequate when built but don’t meet current seismic expectations. Whether any of this needs to be addressed as part of your specific project depends on the scope of work and what the jurisdiction requires, which is worth confirming directly with your local building department rather than assuming.

How This Affects Permits

What gets found during demolition can, in some cases, change what your project needs to include, particularly if structural, electrical panel, or foundation work becomes part of the scope. Permit and inspection requirements vary by project scope and by jurisdiction. San Francisco projects go through the Department of Building Inspection, while unincorporated Marin County projects go through the Marin County Community Development Agency; incorporated Marin towns each have their own building department. If demolition reveals something that changes the project’s structural or systems scope, that’s worth a conversation with your contractor about whether it affects your existing permit or requires an amendment, rather than something to work around quietly.

What to Decide Before Demolition, and What Can Wait

Not every finding needs an answer on day one. In general:

Worth deciding before demolition begins:

Whether you want any suspected lead-containing surfaces tested
Whether a panel upgrade is realistically part of this project or a near-future one
Your comfort level with a contingency allowance for framing or foundation findings

Can typically be decided once the wall is open and the actual condition is visible:

Whether a specific run of galvanized pipe gets replaced now or flagged for a future project
The exact scope of an electrical rewire in a given wall or room
Minor framing repairs that don’t affect the overall structural plan

A contractor who’s done this kind of work in older Marin and San Francisco homes before should be able to tell you, before demolition starts, which category a likely finding is going to fall into. That’s a fair question to ask any contractor you’re considering, and a useful way to compare proposals: not just what’s included, but how each contractor plans to handle what isn’t visible yet.

Budgeting for the Unknown

We won’t publish specific percentages or dollar figures here, since every home and every project scope is different, and unsupported numbers do homeowners more harm than good. What we will say is that a well-structured proposal for an older-home remodel should account for the possibility of unforeseen conditions, rather than assuming a best-case scenario throughout. Ask your contractor directly how they structure allowances for this kind of finding, and how change orders get communicated and approved if something significant turns up.

Frequently Asked Questions

Does every older-home remodel involve opening walls to check wiring and plumbing? Not necessarily. The extent of demolition depends on the project’s scope. A cosmetic kitchen refresh may not expose much, while a whole-home remodel or a project involving structural changes is far more likely to open walls where original systems are visible.

How can I budget for problems I can’t see before the work starts? Ask your contractor how their proposal handles unforeseen conditions, specifically how allowances are structured and how change orders are communicated and approved if something significant is found. A detailed, itemized proposal should address this directly rather than leaving it as an assumption.

Do I need to test for lead paint or asbestos before renovating an older home? If your home was built before 1978, lead-safe work practices are federally required when painted surfaces are disturbed, and your contractor should already be certified to follow them. Whether formal testing makes sense for your specific project is worth discussing directly with your contractor, since it depends on the scope of work and the materials involved.

What is a cripple wall, and why does it matter for a Marin remodel? A cripple wall is a short, wood-framed wall that connects a home’s foundation to its first floor, common in homes built on raised foundations, including many hillside homes throughout Marin. Older cripple walls are often under-braced by today’s standards, and whether yours needs attention depends on your home’s specific construction and the scope of your project.

Can something found during demolition affect my permit? It can, particularly if the finding changes the structural, electrical, or systems scope of the project. If that happens, it’s worth talking to your contractor about whether your existing permit needs an amendment, rather than proceeding without addressing it.