Remodeling an Older Home in Bismarck-Mandan: What's Usually Behind the Walls

Who this is for: owners of Bismarck and Mandan homes built before the 1990s who are planning a bathroom, kitchen, basement or drywall project and want to know what may turn up once the walls are open.

The short answer

Plan for a few surprises, and plan for them before demolition starts. Older homes are the norm here. According to the U.S. Census Bureau's American Community Survey (2020–2024 5-year estimates), the median year built is 1985 for Bismarck's housing and 1981 for Mandan's. About 44% of Bismarck's housing units and 49% of Mandan's were built before 1980.

What turns up depends mostly on when the house was built:

What to look for by the year a home was built (sources in each section below)

Built	What may be behind the walls, floors and ceilings
Before 1978	Lead-based paint, more likely the older the house
Through the 1970s	Asbestos in ceiling texture, joint compound, vinyl flooring, pipe insulation and vermiculite attic insulation
1965 to the mid-1970s	Aluminum branch-circuit wiring
1978 to 1995	Polybutylene water lines
Before 1975 (baths) or 1987 (kitchens)	Outlets near water without GFCI protection
Any age	Old leaks and rot, bath fans vented into the attic or not at all, two-prong outlets, out-of-square framing

None of this is a reason not to remodel. It's a reason to test before demolition, keep a cushion in the budget, and hire a general contractor who remodels older homes in Bismarck-Mandan and has a clear rule for what happens when something turns up.

How old are homes in Bismarck and Mandan?

The 1970s were a building boom in both towns. In the same Census estimates, about 18% of Bismarck's housing units and 24% of Mandan's were built from 1970 to 1979, more than in any other decade before 2010. About 17% of Bismarck's and 18% of Mandan's were built before 1960. That 1970s stock matters because it's where several issues overlap: lead paint until 1978, asbestos-era ceiling textures, aluminum wiring early in the decade and polybutylene pipe starting at its end.

Lead paint in homes built before 1978

The federal government banned the sale of lead-based paint for homes in 1978, and the EPA says a home built before then is more likely to have it. By the EPA's estimates, lead-based paint is likely in 87% of homes built before 1940, 69% of homes built from 1940 to 1959, and 24% of homes built from 1960 to 1977. Sanding, scraping and demolition turn that paint into dust.

Under the EPA's Renovation, Repair and Painting (RRP) rule, anyone paid to disturb paint in a pre-1978 home must be certified, including sole proprietors, and must follow lead-safe work practices. The rule doesn't cover homeowners working on their own homes, but the EPA recommends hiring a lead-safe certified contractor. Ask every contractor for their RRP firm certification, or look them up with the EPA's certified firm search.

If your home was built before 1978 and the work will disturb painted surfaces, ask how that part of the job will be handled, and by whom, before you sign. Testing or specialist work, when needed, is priced and scheduled separately.

Asbestos: popcorn ceilings, old flooring and vermiculite

Until the 1970s, many building products and insulation materials used in homes contained asbestos, according to the Consumer Product Safety Commission. The CPSC says asbestos may be in textured paint and in patching compounds used on wall and ceiling joints, and that their use was banned in 1977. The EPA's list also includes vinyl floor tiles and sheet-flooring backing and adhesives, coated hot water and steam pipes, old oil and coal furnaces, and vermiculite insulation.

• You can't tell by looking. The EPA says a trained and accredited professional should take samples, and that you shouldn't saw, sand, scrape or drill suspect material (EPA).
• Vermiculite in the attic. It's a pebble-like, pour-in insulation, usually gray-brown or silver-gold. A mine near Libby, Montana, supplied over 70% of U.S. vermiculite from 1919 to 1990, and that ore was contaminated with asbestos. The EPA says to assume it contains asbestos and leave it undisturbed.
• North Dakota rules. Single-family homes are usually exempt from the state's asbestos regulations, but the North Dakota Department of Environmental Quality doesn't recommend homeowners remove friable asbestos themselves and publishes a list of certified inspectors and licensed contractors.

A popcorn ceiling can be patched or removed. In one 2026 HHI proposal, popcorn removal for a whole house was priced at $5,000–$7,000, with asbestos testing and abatement handled separately. The year the house was built doesn't tell you what's in the texture, so have it tested before anyone disturbs it.

Wiring: aluminum circuits, two-prong outlets and missing GFCIs

Aluminum wiring. A copper shortage in the mid-1960s led builders to use aluminum for ordinary household circuits. The CPSC's guide to repairing aluminum wiring says cables installed from 1965 to the mid-1970s may be aluminum, and that homes built before 1972 and wired with aluminum were 55 times more likely than copper-wired homes to have outlet connections reach fire-hazard conditions. Look for "AL" or "Aluminum" printed on the cable jacket in an unfinished basement or attic. Warm cover plates, flickering lights or a burning-plastic smell are reasons to call an electrician now, not at remodel time.

Two-prong outlets and GFCIs. A two-slot outlet usually means no ground wire. The CPSC's GFCI fact sheet says a GFCI outlet can replace an ungrounded two-slot outlet if it's labeled "No equipment ground," and lists when the electrical code started requiring GFCIs: bathrooms in 1975, garages in 1978, kitchens in 1987 and unfinished basements in 1990. A kitchen or bath older than those dates may have none.

Smoke and CO alarms. In Bismarck, which uses the 2021 International Residential Code, a remodel that needs a permit also requires smoke and carbon monoxide alarms placed the way the code requires them in new homes (Sections R314.2.2 and R315.2.2). Exterior work like roofing, siding or windows is exempt.

Rewiring and replumbing are jobs for licensed electricians and plumbers, with their own permits.

Plumbing: polybutylene and slow leaks

Polybutylene (PB) is flexible gray plastic pipe joined with plastic or metal insert fittings and small aluminum or copper crimp bands. A national class-action settlement covered PB systems installed from January 1, 1978, to July 31, 1995 (Contractor magazine), and its claim deadline expired in 2009. If you still have PB, replacement is on you, and the cheapest time to replace the runs in a room is when that room's walls or ceiling are already open.

Slow leaks are the other common find, especially around old tubs, showers and toilets. Behind old tile, the usual culprits are tile set on drywall or greenboard, no waterproofing behind cement board, a rotted subfloor at the shower curb, and mold behind tub surrounds.

Bathroom fans that vent into the attic, or nowhere

The IRC (Section R303.3) requires a bathroom to have a window of at least 3 square feet, half of it openable, or artificial light and an exhaust fan, and the fan's air has to go directly outdoors. Some older bathrooms have only a small window, or a fan whose duct ends in the attic. In a North Dakota winter, warm, damp air dumped into a cold attic can condense or frost on the roof sheathing. When a remodel opens the bathroom ceiling, that's the time to run the duct outside.

Framing, floors and earlier repairs

Decades of frost and settling can leave an older house a little out of plumb, out of level and out of square. That matters for tile, cabinets and vinyl plank, which all need a flat, square base, so leveling and shimming can be part of the scope. Earlier remodels can also leave cut framing or patched-over damage that only shows up during demolition. Signs of foundation movement, or a load-bearing wall in the plan, call for a licensed structural engineer.

What it means for your budget

Set aside a contingency, and keep it separate from upgrades. For a benchmark, HUD's 203(k) renovation loan program requires a contingency reserve of 10% to 20% of the repair costs on homes 30 years or older. A 1985 house is past that mark. Your number depends on the home's age, its history and how much of it you're opening up.

• Test first. Paint and suspect materials tested before demolition can change the scope and schedule, and it's cheaper to know before the crew starts.
• Compare how estimates handle hidden conditions. Our hiring checklist that covers how hidden damage is priced lists the questions to ask.
• Plan how you'll pay for surprises. See how to pay for a remodel, including a cushion for surprises.

What happens when we find something

If we find something behind walls or floors, like water damage, rot or framing problems, we show you, explain your options, and price it clearly before going further:

1. Stop work in that area.
2. Show you what we found, in person or with photos.
3. Explain the options, from a spot repair to a full replacement.
4. Price it in writing. Any repair outside the written scope is priced and needs your approval before we continue. If opening a wall reveals a new concern, we document it and discuss the next step before disturbing more material.

For the full sequence, see what happens at each stage of a remodel with us. If you'll be home during the work, read our guide to living at home while the walls are open.

Frequently asked questions

What problems are common when remodeling a house built before 1980?

Lead-based paint (before 1978), asbestos in ceiling texture, joint compound, flooring or vermiculite, aluminum wiring in some 1965 to mid-1970s homes, and kitchens and baths without GFCI outlets. Any older home can also hide old leaks, rot, and bath fans that don't vent outside.

Do I need to test for lead paint before remodeling?

If the home was built before 1978, plan on it. Any contractor paid to disturb that paint must be RRP-certified and follow lead-safe practices under the EPA's rule, and testing, or treating the paint as lead-based, tells everyone what setup and cleanup the job needs.

Does my popcorn ceiling have asbestos?

You can't tell by looking. The CPSC says asbestos may be in textured paint and joint compounds, whose use was banned in 1977. The EPA recommends having a trained and accredited professional take samples before anyone scrapes, sands or drills the ceiling.

Should I replace polybutylene pipe during a remodel?

If a remodel opens the walls or ceiling where PB runs, that's usually the cheapest time to replace it. The class-action claim deadline expired in 2009, so the cost is yours either way.

How much contingency should I budget for an older home?

It depends on the house and the scope. As a benchmark, HUD's 203(k) renovation loans require a 10% to 20% contingency reserve on homes 30 years or older. Keep it separate from upgrades so it's there if the walls hold a surprise.

Own an older home and planning a remodel? We'll walk the house with you and give you a free written estimate that explains how hidden conditions are handled. Call or text Viktor at (701) 329-9659 with your town, photos and what you want to change. Our office follows up during business hours. Hugo Home Improvement (Hugo Home Improvement LLC) holds North Dakota Contractor License No. 000050538.