From the sidewalk, you usually can't identify synthetic stucco by sight. Either system can be finished smooth or textured and in any color. Building-envelope engineer Brian Erickson makes the point in his Lerch Bates guide to telling them apart: the finish coat on every system "can be applied in similar colors and textures." What differs is what sits underneath, and that you can check with your hands.
It's worth knowing before you make an offer, because the answer decides your next step. If the walls are traditional stucco, your general inspector looks at them along with the rest of the exterior. If they're EIFS, the real question is what's behind the foam, and answering it takes a dedicated EIFS stucco evaluation.
What EIFS (synthetic stucco) is, and what stucco is
Traditional stucco is cement plaster. The 2021 International Residential Code (IRC Section R703.7) has it installed to ASTM C926 and ASTM C1063. On a framed wall it goes over metal or wire lath, and the code requires at least three coats over that lath. The code's plaster-thickness table calls for at least 7/8 inch of cement plaster over wire lath on an exterior wall. The result is heavy, hard and dense.
EIFS (exterior insulation and finish system, often sold as "synthetic stucco") is foam insulation board with a thin reinforced coating on top. In the most common type, Erickson puts that base coat at typically 1/16 to 3/32 of an inch, with fiberglass mesh embedded in it. The code covers it in a section of its own, IRC R703.9.
One is a thick shell of cement. The other is foam with a thin skin over it. Each check below is a way of feeling that difference.
Five checks you can make at a showing
Ask the listing agent before you touch the walls. Test a plain stretch of wall, not the trim around windows and corners (the next section explains why).
1. Tap it. Knock lightly with your knuckles. A hollow sound points to EIFS. A solid sound points to stucco's thicker base coat. The limit: Erickson notes that a less common EIFS type with a thicker, mechanically fastened base coat can also sound solid, and so can hybrid stucco systems.
2. Press it. Push firmly with your thumb. If the wall gives a little, that points to EIFS. No give points to stucco, or to one of those thicker systems. Don't push hard enough to hurt your hand or mark the finish.
3. Read the cracks. Traditional stucco can crack out in the open part of a wall. Properly installed EIFS of the common type usually doesn't crack there. Where it does, the cracks tend to be small and close to penetrations such as light fixtures and vents. Hairline cracks across a wide area point to stucco.
4. Look for control joints. These are straight lines tooled into a wall, dividing a large surface into panels. They suggest stucco, or one of the thicker EIFS types. Don't mistake them for expansion joints, which belong at floor lines and where the wall behind changes, on both systems.
5. Look at the bottom edge. For stucco on a stud wall, IRC Section R703.7.2.1 calls for a weep screed: a metal or plastic strip at or below the line where the wall meets the foundation. It must sit at least 4 inches above soil or 2 inches above paving, so trapped water can drain out. EIFS must stop at least 6 inches above the finished ground (R703.9). A clear weep screed is a clue toward stucco, not proof. An older house may not match today's code at all.
No single check settles it. If two or three point the same way, you have a reasonable working answer.
Where the checks fool people
- Foam trim on a stucco house. Foam shapes can be glued onto a stucco wall to make window surrounds, bands and corners. Erickson is explicit that this does not make the house EIFS. Tap and press the flat wall, not the trim.
- The finish. The same textured coating can go on either system, so a finish that looks soft proves nothing.
- Distance. Erickson calls the two "extremely difficult" to tell apart from a short way off. Get close enough to touch.
If it's EIFS, your hands can't answer the next question
The code treats the two kinds of EIFS very differently.
- Barrier EIFS has no built-in way for water to drain out. The 2021 IRC limits it to concrete or masonry walls (Section R703.9.1).
- EIFS with drainage is required on every other wall, including wood framing (Section R703.9.2). It needs a water-resistive barrier between the EIFS and the sheathing, and a tested drainage efficiency of at least 90 percent.
Older houses were built under whatever code their town had adopted at the time.
From outside, you can't see which kind is on the wall, or whether water has already got behind it. A specialist moisture survey answers both questions. Our report engine puts it at $400 – $800 for a moisture survey by an EIFS-qualified inspector, and the EIFS evaluation guide explains what that inspector does. If you're deciding whether to make or keep an offer, should you buy a house with EIFS? sets out the order to do things in.
If it's traditional stucco
Ask your general inspector to name the cladding type in the report. Ask them to point out any cracking or staining, and to look at the bottom edge and the joints around windows and doors. If they see signs of water getting in, ask whether they recommend a specialist, and get that answer in writing before your inspection period ends.