Do I need a chimney liner when I convert from oil to gas in New Jersey?

New Jersey Chimney Co. · October 13, 2026

Who is still heating with oil

Statewide, New Jersey is a gas state. The Census Bureau's 2024 American Community Survey puts utility gas as the main heat in 73% of homes, against 47% nationally, and fuel oil at about 6%. But oil is concentrated in a few places. In Sussex County, 48% of homes still heat with oil. Hunterdon and Warren are at about 25% each, Salem at 23%, Cumberland at 14% and Morris at 12%.

Those are the counties where oil-to-gas conversions happen most, and where we see the most chimneys that were built for an oil boiler and are now being asked to carry gas exhaust.

Why the chimney is part of the conversion

New Jersey's chimney verification form, F-370, has a specific set of statements for liquid or solid fuel converted to gas. The person signing must confirm the chimney is in good repair and clear, that it is substantially clean of residue from its previous use, and that it is appropriately lined and sized for the new appliance. A homeowner cannot sign it, and towns ask for it with the heating permit.

Notice what the form does and does not say. It does not say every conversion needs a new liner. It says the chimney has to be right for the new appliance. Whether yours is depends on what is in it now and what is going in.

Why old oil flues often fall short

Oil burners leave soot and scale in the flue, which has to come out before anything else is judged. Under that, many older chimneys have clay tile liners with cracked tiles or open joints, and some have no liner at all. A reply in a City-Data New Jersey forum thread put it simply: heat, rain and ice crack flue tiles over time, and cracks hurt the draft.

Size matters too. A new high-efficiency gas furnace or boiler usually sends less, cooler exhaust up the chimney than the old oil burner did. In a large, cold flue that exhaust can condense on the way up, and the moisture works on mortar and tile. The New Jersey fire code is clear about the worst case: a masonry chimney found without a liner, with open mortar joints that let smoke or gases into the building, must be repaired or relined.

Your venting choices

Every conversion ends up in one of these places, and the free inspection tells you which one fits your chimney and your new equipment.

• Reline the chimney: a stainless or aluminum liner sized for the new furnace or water heater, typically $625–$2,250. Larger stainless jobs run $1,500–$5,000.
• Coat the existing flue: liquid-applied lining is ordinary maintenance under N.J.A.C. 5:23-2.7; cast-in-place liners typically run $2,000–$7,000. Whether a coating suits your appliance depends on the product.
• Skip the chimney: many high-efficiency units vent directly through the wall. The same City-Data thread noted that only newer high-efficiency units can be vented this way.
• Watch the water heater: if the furnace goes direct-vent but the water heater stays on the chimney, the flue may now be too big for the water heater alone.

What to do with a chimney nobody uses

If both the heating system and the water heater leave the chimney, it still sits on your roof taking rain and freeze-thaw. At minimum it should be capped and the crown kept sound; a cap typically runs $250–$850 and crown work $600–$2,200. Some owners take an unused stack down below the roofline, which typically runs $1,000–$2,500, and have the roof patched over it.

The order that saves money

Get the chimney checked before you sign the heating contract, not the week of the install. That way the liner, if one is needed, is sized for the actual unit, the paperwork for the F-370 is ready with the permit, and nobody is waiting on a liner with the old boiler already removed. Our inspection is free, with photos and a written price, and we work Sunday through Friday in three-hour windows.