Injection foam for existing walls in older Cincinnati houses

If your house is cold at the walls and you are not about to tear out plaster, injection foam is the obvious question. It is also the question where the answer depends most on what the wall is actually made of. Before anyone talks price, find out whether your walls have a cavity to fill.

First question: is there a cavity at all?

A lot of older Cincinnati housing is brick, and brick comes in two very different kinds of wall.

• Solid masonry. Two or three layers of brick laid together, with plaster applied to the inside face or to thin furring strips. There is no stud bay to fill. This is common in older city houses in Cincinnati, Covington, Newport, and Bellevue.
• Brick veneer over a frame wall. A single layer of brick outside a wood-stud wall, with a hollow bay between the studs. These walls can usually be filled.

A quick way to tell them apart is the brick pattern. Solid walls tie their layers together with header bricks laid end-out, usually in a row every five to seven courses. A veneer wall shows only the long faces of the bricks. Wall thickness at a window jamb is another clue, since solid brick is noticeably thicker. Frame houses with wood, vinyl, or aluminum siding almost always have stud bays.

Walls that qualify, and walls that do not

Good candidates:

• Empty stud bays in older frame houses, a common find in Norwood, Hyde Park, and Fort Thomas
• Brick veneer over studs
• Walls with thin, slumped old insulation, although fill results vary and a thermal scan afterward matters

Proceed with care:

• Balloon framing. Many older frame houses have studs that run from the sill to the roof with no break at the floors, so the bays are open at the top and bottom. They need blocking first, or the foam ends up in the basement or attic.
• Knob-and-tube wiring. The electrical code bars it from cavities filled with foamed-in-place insulation that surrounds the conductors, so live runs have to be replaced first.
• Painted plaster in a pre-1978 house. The EPA's Renovation, Repair and Painting rule requires paid work that disturbs painted surfaces in homes built before 1978 to be done by a lead-safe certified firm, so ask for the certification.

Poor candidates:

• Solid masonry with no cavity
• Walls with active leaks, rotted sheathing, or failed window flashing (fix the water first)
• Bays already full of intact batts, where there is little room left to fill

Injection foam is not the same product as spray foam

The foam sprayed onto an open roof deck or rim joist is a two-part polyurethane that expands fast and hard. Injected into a closed wall, that expansion can push plaster off its lath or bow drywall. Wall injection uses products made for closed cavities: lower-expansion or slower-rising foams, some polyurethane and some resin-based. Branded systems such as RetroFoam are typically installed from outside by removing a strip of siding and drilling each stud bay; other approaches go in from inside through small holes in the plaster that are patched afterward.

Because formulas differ, compare data sheets, not brochures. Ask for:

• The product name and its published R-value per inch
• How it expands and cures, including any shrinkage specification
• Whether it is intended for closed-cavity retrofit
• How each bay is checked to confirm it is full

What it costs

Pricing follows the number of bays, the access, and the patching. Our wall cavity foam pricing puts drill, fill, and patch at roughly $200 to $300 per bay, which lands many 2,000 square foot pre-1950 houses between $8,000 and $18,000 for the full exterior. Specialist plaster restoration adds to that. Installing from outside through a removed siding course avoids interior patching but adds siding work. A single cold room is a far smaller job, and often the right place to start.

How long it lasts

Inside a dry, closed wall, cured foam has almost nothing working against it: no sunlight, no foot traffic, no settling. What shortens its life is water coming in from outside, through failed window flashing, gutters spilling onto siding, or a leaking brick sill, and shrinkage in products that shrink as they cure, which leaves a cold gap at the top of the bay. Both show up on a thermal camera on the first cold morning, which is why a scan after the work is worth asking for. Ohio's residential code does not require a retrofit wall to reach new-construction R-values when the cavity is not opened, so filling the empty bay completely is the realistic goal.

Before anyone drills

• Identify the wall type on each side of the house
• Have an electrician confirm there is no live knob-and-tube in the walls to be filled
• Check window flashing, gutters, and downspouts on those walls
• Get the product data sheet and the plan for confirming each bay is full
• Ask who patches the plaster, and ask to see their patches on another house

For more on the process, see the existing walls FAQ, the historic home FAQ, and a Hyde Park plaster-wall example. If you live in Norwood, wall foam in Norwood has local notes. Call or text us a photo of your brick or siding and we can usually tell you whether your walls have a cavity at all.