Four things cost money. One is local.

An Eichler roof is not a pitched roof with shingles. It is a low-slope membrane over exposed decking with no attic above it, and a roofer who has not done one will quote it wrong and install it worse.

Bay Area figures published by GMJ Construction as 2025 planning benchmarks: spray polyurethane foam at $6–$12 per square foot, roughly $12,000–$24,000 on a 2,000 square foot roof. TPO runs about the same. PVC is higher at $8–$15, so $16,000–$30,000. Their stated Bay Area average across roof types is about $28,500 before anything Eichler-specific.

Those are 2025 benchmarks and the source says so. Treat them as the shape of the number, not a quote. The sequencing matters more: a re-roof is the moment to deal with insulation and any penetration, because the deck is open. And if your house has the 1968 outrigger beam ends, tell the roofer before they start — those get removed by people who do not know what they are.

GMJ Construction’s Bay Area figures, published October 2025: a fixed insulated glass panel of roughly four by eight feet runs $3,000–$5,000 installed, and an elevation of three to five panels comes to $9,000–$25,000. Sliding glass wall systems run $900–$2,000 per linear foot. A full elevation spanning sixteen to twenty-four feet lands around $15,000–$40,000 and up. Permits add $250–$600.

The federal Energy Efficient Home Improvement Credit covers thirty per cent of qualified cost but caps at $600 a year, which on these numbers is a rounding error.

Replacing every pane on a house that has held up for sixty years is rarely right. Replacing the failed units and the worst elevation usually is.

Eichler heated these houses with hot water run through tube cast into the concrete slab. No ducts, no registers, no radiators — which is precisely why the walls could be glass. After sixty years some original systems have failed.

We are not going to publish a repipe figure. There is no independent, Eichler-specific one we can stand behind, and the general Bay Area repipe numbers online are for domestic water supply, a different system and a different trade.

What is specific to Foster City is what the slab sits on: engineered hydraulic fill over former bay marsh. We looked for any study of slab-on-grade foundation performance on Foster City fill and found none — no city report, no geotechnical paper, nothing. We are not going to speculate in either direction. What we would say is that a slab here deserves a proper look during inspection rather than a glance, and that a pressure test of the radiant loops should come before any quote, as it should anywhere.

Original Eichler roof and wall assemblies carry very little insulation, and the single-glazed walls do the rest. That is where the heating bill comes from, not from the radiant system being inefficient.

Fix the envelope when the roof is already open, then decide about the heating. The other order means paying twice.

Beyond that, an Eichler is a post-and-beam house on a slab. Kitchens, bathrooms, electrical and sewer laterals cost what they cost on any house of the period.