Walk into an Eichler that still has its original heating and you won’t see vents. The warmth comes from the floor. That one design choice shapes how these homes are inspected, repaired and bought.
Eichler radiant heating is a hot-water system. Pipes are cast into the concrete slab, a boiler warms the water, and the slab releases that heat upward into the rooms. It’s simple when it works. When it doesn’t, the pipes are underneath the concrete. That’s why buyers ask about the system early, and why it helps to understand how it’s built.
How the original system works
Eichler’s builders poured hot-water pipes into the concrete slab that forms the floor of the home. A boiler heats the water, and the water flows through loops in the slab. The warmed concrete radiates heat into the room. Most homes have one or two zones, each with its own thermostat.
The pipe material depends on the era. Systems from the early 1950s used steel, and later systems mostly used copper. Which one a particular home has depends on when it was built and what has been replaced since. A tract that looks uniform from the street doesn’t guarantee a uniform system. The San Mateo Highlands, built between 1956 and 1964, is a good example. Homes built to the same plans can heat differently today, depending on what each owner has repaired, replaced or abandoned. The San Mateo County neighborhood guide shows how much neighborhoods on the Peninsula differ from one another.
How the system fails, and the signs
Steel pipe corrodes. After several decades it can rust through, and contractors interviewed in the Eichler Network article Joint of No Return say repeated repairs to a steel system tend not to hold. Copper lasts far longer. One radiant contractor in the same article calls failures that force an owner to abandon a system rare in his work. Leaks often develop near expansion joints or cracks in the slab, and pinhole leaks are the most common kind.
A leak in a slab is hard to see. Owners and inspectors look for a rising water bill, hot spots on the floor and the sound of running water when everything is shut off. Cracks in the flooring, mildew under carpet and a white powdery deposit along the foundation outside are other signs. Uneven heat is another sign. The floor can warm in stripes where the tubing runs and stay cooler in between.
What owners do about a failed system
A failed system doesn’t have one fix. The first step is finding the leak, which contractors do with thermal imaging, pressure testing or helium detection, according to this guide to radiant heating in Eichler homes. A single leak can sometimes be repaired with localized work in the slab. A system with many leaks is a different decision.
Owners who want to keep radiant heat can have the slab cut with new grooves and fit new PEX tubing. They can also install a panel system with channels for tubing over the existing floor. Others give up on radiant heat and heat the home another way, with forced air, baseboard units or ductless heat pumps. Re-grooving means cutting into the finished floor. A forced-air conversion means adding ducts to a home that was designed without them.
The questions that settle what the system is worth
The pipes can’t be inspected from above, so the visible clues are the evidence. Patched concrete, space heaters in the living room and added wall units often mean the radiant system had trouble in the past. A few questions then fill in the rest. What are the pipes made of? Steel and copper age very differently. When was the system last repaired or replaced, and is there a record? A pressure test confirms whether the system is holding, which a verbal “it’s been fine” can’t. How old is the boiler, and does every zone heat evenly? Uneven heat points to trouble in the loops. Sellers can gather those records before listing. This guide to preparing a Bay Area home for sale covers the wider checklist, and the page on selling your home covers the process.
Frequently asked questions
Do all Eichler homes have radiant heating?
Most were built with it. Some original systems have since been replaced or abandoned. The present system has to be confirmed for each home.
What’s the difference between steel and copper pipe?
Steel corrodes and tends to fail first. Copper doesn’t rust. It can last much longer.
Can a leak be fixed without replacing the whole system?
A single leak can sometimes be repaired once it has been located. Whether that makes sense depends on the pipe material and how many repairs the system has already had.
How do you find a leak under a slab?
Contractors use thermal imaging, pressure testing or helium detection. Owners usually notice the symptoms first. Hot spots and a higher water bill are common ones.
What the heating says about the home
In an Eichler the heating system is built into the floor. Its material, age and repair history belong in any conversation about the home’s condition, because they decide what the floor will need next. If you’re buying or selling an Eichler in San Mateo County, I’m happy to go through the heating records, or the disclosure packet, with you. For background on the style itself, see this guide to mid-century modern architecture.
About the Author:
Mark Tauber is a San Mateo County real estate agent who works with buyers and sellers across the San Francisco Peninsula.
