Aluminum Wiring, Polybutylene Pipes and Other Old Building Systems: Due Diligence for Apartments
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A sponsor buys a 1970s building, plans a cosmetic renovation and then learns the walls hold aluminum wiring and the supply lines are polybutylene. Neither shows up in a photo. Either can change the insurance quote, the lender's report and the capital budget. This post explains what to look for and how to price it before closing. It is part of our guide to apartment property due diligence. It is general information, not legal, engineering or investment advice.
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The systems to ask about
| System | Era often cited | Why it matters |
|---|---|---|
| Aluminum branch wiring | Roughly the mid 1960s to the mid 1970s | Connections can loosen or overheat over time, which concerns insurers and inspectors |
| Polybutylene supply pipes | Roughly the late 1970s to the mid 1990s | A history of leaks and failures, and insurer scrutiny |
| Certain older electrical panels | Varies by brand | Some are flagged by inspectors and carriers |
| Cast iron drain lines | Older buildings | Can corrode and crack, with costly repairs |
| Original boilers, HVAC and roofs | Any age | Near end of life, see the capital plan |
Eras are rough. Ask the inspectors what they actually find in this building. For lead and asbestos, see lead based paint rules and asbestos surveys.
Step 1: Ask before you spend
Ask the seller for permits, upgrade records and any past claims. Ask the property manager about leaks, outages and tripped breakers. A pattern of repeated plumbing or electrical calls is data.
Step 2: Inspect during the contingency period
Order a general inspection and add targeted ones.
- A licensed electrician to open panels, test sample units and look at the wiring type.
- A licensed plumber to identify pipe materials, run camera scopes on drain lines and review the water heater setup.
- The lender's property condition report. See lender third party reports.
Inspect a spread of units, not only the model.
Step 3: Call the insurer early
Insurance quotes may change with the building's systems. Ask your broker, in writing, what the carrier needs to see and what it would exclude or surcharge. See apartment insurance costs. Do this before your contingency ends, when you can still walk away or renegotiate.
Step 4: Price the fix
Get at least two bids. Repair or replacement can involve opening walls, relocating residents and doing unit by unit work, which affects timing and income. Account for:
- Cost per unit and for common areas.
- Lost rent while units are down. See renovation pace and lease up.
- Permits, inspections and contingency.
Then decide: ask for a price cut or a credit (see repair credit vs price reduction), put it in the business plan (see property improvement plan), or pass on the deal.
A hypothetical example
This is an illustration with made up numbers, not a bid. Inspectors find polybutylene supply lines in an 80 unit building. The plumber's bid for repiping comes to $2,400 a unit, or $192,000 in total ($2,400 times 80). The sponsor can negotiate a credit, add the amount to the capital plan or walk away. If it is added to the plan, the equity raise needs the extra $192,000 and the timeline needs to allow for unit by unit work.
Questions investors can ask
- Did inspectors check the wiring and plumbing materials? What did they find?
- Has the insurance carrier reviewed the building? Any exclusions?
- Is the cost of any fix in the sources and uses?
How DoorRaise fits in
DoorRaise does not inspect properties. The sponsor handles due diligence, and DoorRaise handles the raise, the deal company, the investor paperwork and escrow. Sponsors pay a flat $1,500 setup fee and a flat $5,000 yearly administration fee.
Frequently asked questions
Can I still buy a building with aluminum wiring?
Often yes. The questions are what an electrician recommends, what the insurer will do and what the lender requires.
Does polybutylene always fail?
No, but it has a history of problems and insurers pay attention to it. Have a plumber assess the actual condition.
When should I call my insurance broker?
During the inspection period, before you remove contingencies.
Sources
This article is general information as of November 2026, not legal, tax or investment advice. Every investment can lose money. DoorRaise is not a law firm, broker-dealer, investment adviser or funding portal.