Stucco Classico: Plaster Repair for 19th Century (and earlier) Homes

We serve eastern and western Pennsylvania and vicinity.

Up to 1910s: One or two coats of lime stucco, followed usually by a finishing coat of putty lime and gauging plaster.  Sometimes, earlier homes used clay in varying amounts.  This was the norm through the beginning of the twentieth century.  For small repairs we use a softened plaster/lime stucco mix--a hard mixture can actually damage your existing plaster.  For larger repairs we can do either a lime stucco base like the original (lime stucco is a superb material, please see our page on lime) or we can substitute a soft plaster mix.  Repairs using a proper lime stucco can be especially important on the insides of exterior walls on older homes, since often this material was applied directly to the masonry or stone base, with no lath or furring.  Lime stucco is a superb material for new work, interior or exterior; please see our page on lime stucco

Lime stucco will withstand seapage or condensation that is typical of these types of installations while remaining moisture-permeable, allowing your walls to breathe.  Gypsum plasters such as Structo-Lite are not recommended for these uses even by the manufacturer (USG).  Moreover, lime naturally inhibits mold.

The typical minor issues experienced with this sytem are fairly irregular cracking and the usual dings, chips, etc.  Cracks may extend from the corners of doors and windows.  Cracks very often follow joist or stud lines (roughly), since these areas are usually the weakest.  For cracks larger than hairline we use proprietary acrylic- based adhesives to re-attach, since the cracks are usually the result of some looseness.  Many folks will repair such problems by resurfacing with skim coat (with or without mesh).  This is not the proper way to repair these problems.  This only recovers the surface, and does nothing to address the underlying problem: loose basecoat plaster.  Moreover, since resurfacing is usually done with drywall mud, the new surface is usually inferior to the old (much softer and not so long-lasting).  If the drywall mud is the ready-mixed type, it is also more vulnerable to water.  We also generally avoid taping cracks, since this leaves a diificult-to-disguise bump.  Again, it covers the problem rather than address the root of it (looseness).

It is also important to find the root of the plaster problem first.  It is not uncommom to find that the root cause of the problem is defective framing.  Sometimes, joists are too small and weak, and therefore flex too much.  You can test joists by walking or gently jumping on a floor while another person watches and feels from below.  In the instance where joists move too much, plaster repair may not be the answer.  To determine the maximum tolerable movement, divide the distance spanned by 360.  Anything less than this number is considered acceptable.

Sometimes lathing is improper.  Joists or studs cannot be too wide or sistered behind wood lath as this will prevent plaster from "keying" properly.  When repairing lath, we try to avoid or severely limit our use of metal lath with wood lath.  It is best to not mix the two materials due to their very different coefficients of moisture and thermal expansions.

Here is a sample repair to three coat plain and ornamental plaster:

Repair of Lime Stucco with Ornamental Gypsum Moulding

For expert plaster repairs, contact Stucco Classico.