Restoring Historic Structures with Lime

 

The same seasoned slaked lime used in popular Vero products like Antiqua and Epoca Spatolato is ideal for restoring historic masonry buildings.  Vero can provide the technical assistance and products to restore many U.S. buildings of significance, including:

• Adobe buildings such as the California Missions
• Brick buildings
• Stone buildings
• Interiors done over masonry or traditional wood lath

“Lime is an excellent material for repairing and protecting old buildings, particularly where existing materials must be conserved.”[1]

This adobe wall would be an ideal surface for lime mortar

This sandstone wall in Monterey, CA is currently being restored using Vero lime mortars and lime paint

So call on Vero and we’ll adapt the traditional Italian restoration techniques to your project here in the U.S.

Why Seasoned Slaked Lime?

Lime is the right material for these structures, because of its breathability, durability, and ease of maintenance.  Plus, the hard feel of cured limestone hides an inner softness that gently coats and supports masonry units without breaking them (like Portland cement products will). 

            “Lime plaster is extremely strong stuff that has withstood hundreds of years of weather.  Moreover, because it is pliant (somewhat flexible), lime plaster is not likely to crack very much as a building shifts or where walls expand and contract in response to natural temperature fluctuations or as moisture levels rise and fall… In addition, lime plaster and earthen materials expand and contract similarly.  Consequently, when lime plaster is applied on an earthen wall or an earthen plaster, it is less likely to crack or peel off a wall.”[2]

In addition, lime mortars are historically appropriate for many older buildings in the United States.  Why?  Because lime mortars and plasters were traditionally used for interiors and exteriors prior to the introduction of Portland cement in the early 20^th century. 

            “Before Portland cement became available, lime concretes were used for many applications… The binder used in the original construction of most historic buildings is frequently lime, making this the natural choice for compatible repair material”[3]

What Products Are Best?

We recommend Malta Grezza (coarse mortar) and Malta Fine (fine mortar) for restoration projects.  These products are based on the same seasoned slaked lime used in Vero lime plasters, subjected to an accelerated aging period of 3 months.  This is the best lime on Earth for building – dolomitic limestone, consisting of a mixture of calcium and magnesium oxides.  “Where magnesium limes are used they have a very high reputation, giving an early set and developing good strength.”[4]  These products come ready to use and pre-sanded with a precise mixture of aggregate ideal for these applications. 

Malta Fine & Cocciopesto were used to restore this 150-year-old stone home in Santa Croce.

Note the natural pink color from the Cocciopesto.

The traditional Italian mortar is “spiked” with a small amount of Cocciopesto for added durability, workability, and water repellency.  Typically obtained from crushed clay bricks, Cocciopesto gives Malta Grezza/Fine their characteristic pink color.  Cocciopesto is technically a Pozzolan, which starts a natural slow chemical reaction with the lime, so that all material mixed must be used that day or it will set and be unusable.

Once the lime mortars have been applied to restore the integrity of the walls and ceilings, any Vero lime plaster or paint can be applied for a more smooth and refined finish.  The use of lime throughout the wall, as base and finish coat, will ensure the wall is protected from the elements and properly manage moisture the same way as when the building was originally erected.

Lime paint, such as our Epoca 800, is especially well suited as a finish coat over lime mortars.  Not only does it give a beauty and depth to a building, but it also makes lime plaster even more durable.

            “[Limewash] gives a smooth coating which, after an initial wetting, encourages an easy run-off of rainwater.  At the same time the nature of this surface allows good, all-over evaporation which helps the wall to dry out.  Limewash is unaffected by the ultra-violet rays in sunlight which destroy synthetic paints.”[5]

What is the Application Process?

1)    Remove any loose coatings and foreign material from the wall.  Also remove any paint, as that will prevent the bond of the lime mortar to the wall.

2)    Repointing of masonry units, if needed, should be done with Malta Grezza in lifts of not more than ¾”.  Injection is also a viable repair method for reinforcing the mortar between bricks/stones.

3)    The first coat of lime should be a very thin coat of Malta Grezza, about 1/8”-1/4” thick.  This can be brushed or troweled on a pre-moistened wall.

4)    After 24 hours, the second coat of Malta Grezza, can be applied, up to ¾” as needed.  The first coat should be pre-moistened to slow moisture loss.

5)    After 2-3 days of cure time, an additional coat of Malta Fine (fine mortar) can be applied at 1/8” thickness, if desired.

6)    The day after application, the cracks can be closed up using a sponge float and water.  Wait 2-3 days for additional coats.

7)    When ready for the finish coat, there are many options available (i.e., Antiqua, Epoca Marmo, Epoca Spatolato, and Epoca 800).  The most traditional finish is to apply Epoca 800 lime paint over the Malta Grezza/Fine within 3-5 days.  By applying the lime paint when fresh, the lime paint cross-links with the lime in the mortar, creating a strong bond with no tendency to peel over time and strong natural water-resistance.

Malta Grezza & Cocciopesto were used to restore the trims on the Palazzo Vivante after 150 years                                                    

What if I Really Want to Seal It?

Nature has provided for us with lime paint (Epoca 800) and its ability to form a strong water-resistant finish over lime mortars.  However, if a chemical water repellent is desired, wait a month for the curing to begin on the lime mortars.  Then apply a water-based siloxane primer, such as Rialto Durasil.  Lime paint can be applied after 48 hours, normally in two coats, a day apart.

What do they do in Italy?

The process in Italy is constantly ongoing.  If you travel there, you see plasterers are constantly occupied, restoring old buildings one at a time in a continuous cycle.  Probably the building they restore today was restored by their grandfather before them.  They use the same process and the same materials as we have outlined here.  They use Malta Grezza and Malta Fine with Cocciopesto, taking care to remove any loose material, repointing as needed, and finishing with a “fresh on fresh” coat of lime paint.  In fact, the Colosseum in Rome was recently restored using injected seasoned slaked lime mixed with Cocciopesto from our supplier, Rialto. 

The Palazzo Vivante is a good example of what these products can do.  As pictured below, the building was badly damaged.  Columns needed to be repaired.  The architectural trims had been especially badly damaged from exposure to the elements.  Owners of the building had not periodically repaired and painted with lime paint to prevent damage.

The repair team used a running template to restore the original trims on the building.  Malta Grezza and Malta Fine were used to fill and refinish.  And Epoca 800 lime paint was used in a rich yellow color to beautify and protect the building.

Palazzo Vivante, an
1844 Trieste
landmark shown prior
to restoration using
Malta Grezza and
Epoca 800 lime paint

                                              Palazzo Vivante after restoration

What if the Existing Surface is Unstable?

The receiving surface must be firm enough to support plaster prior to application.  The wall will only be as strong as its foundation.  If the existing walls are powdery, they need to be carefully cleaned until a strong enough base can be reached.

There are other alternatives to firm up damaged walls.  A few coats of dilute lime milk (made from seasoned slaked lime called Grassello di Calce) can be effective, especially in stabilizing earthen and stone materials.  Also, a surface hardener such as Vandex Mineralit can be useful for this purpose.

What if I need to Freshen it up?

Lime products allow for periodic maintenance.  Any major damage can be repaired with Malta Grezza and Malta Fine, taking care to finish the surface with the same texture and level as the original.  Then a new coat of Epoca 800 lime paint can be applied to freshen up the appearance and renew the protection of the building.

            “The regular application of a thin coat of limewash is a very old method of stone preservation which is particularly effective with limestones.”[6]

When restoring historic structures, the old way is best.  Use lime mortars and finishes to provide vapor permeability, protection from water, gentleness on masonry units, crack-resistance, resistance to fire, mold, and mildew, and a wide range of attractive finishing options.  Vero will bring the old-world products to the U.S., and help adapt them to your next challenging historical restoration project.

      The look of Epoca 800 is warm and natural, used here to recolor a stained building

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[1] Holmes & Wingate, Building with Lime, ITDG Publishing 2002, p. 5

[2] Guelberth & Chrias, The Natural Plaster Book, New Society Publishers, 2003, p.165

[3] Holmes & Wingate, Building with Lime, ITDG Publishing 2002, p. 5

[4] Holmes & Wingate, Building with Lime, ITDG Publishing 2002, p. 15

[5] Holmes & Wingate, Building with Lime, ITDG Publishing 2002, p. 49

[6] Holmes & Wingate, Building with Lime, ITDG Publishing, 2002.  p. 49