My wife and I are the head ushers at our church. Each Sunday, we arrive early and walk up a ramp that allows those attending mass in a wheelchair an easy way into Sacred Heart Church in Laconia, New Hampshire.
The church is a stunning redbrick edifice built by French Catholics in the late 1800s. At that time, there were competing factions of Catholics in Laconia, and Catholics from each country built their own church. It must have been like sports rivalries of today.
Based on the churches that are still standing in Laconia, it’s obvious to me that the French had more money and poured lots of it into this magnificent building I worship in each Sunday.
The wheelchair ramp was built perhaps 20 or 30 years ago with two poured concrete walls and the ramp in between. The contractor tried to make it match the original red brick. Rather than pigment the concrete (yes, you can add dry color pigments to concrete), he applied a thin cement stucco to any exposed concrete.
Using the stucco was not a bad idea, and my guess is that it might have been a budget issue. The contractor could have installed a matching brick veneer to the poured concrete for an even better look. They could have done exactly what the architect and builder did who created a stunning addition on the public library in the nearby town of Bristol. The builders there matched the red brick of the original library building perfectly. Only a trained eye can detect that part of the library building is an addition.
Unfortunately, the thin stucco coating has peeled off the poured concrete on the ramp at Sacred Heart. The stucco failed to bond for several possible reasons. It could be one or all of the following:
- The poured concrete walls could have been dusty.
- The stucco batch might not have had enough Portland cement in it or it might not have been thoroughly mixed in with the sand before the water was added.
- The stucco material could have started to set up, and some of the crystals may have already grown and were not able to grab well onto the concrete.
- The stucco may not have been properly cured so the crystals could continue to grow for days and weeks after the stucco was applied.
So, how can you apply cement stucco to poured concrete and make it last for hundreds of years?
The first thing to do is use water and a scrub brush to clean the surface to which you’re applying the cement stucco.
Next, it’s important to make the stucco mix very strong. I was trained how to do this by a master mason when I first got into the construction business. His stucco formula of three parts medium sand, one part Portland cement and one-half part hydrated lime has never failed me.
Blend these ingredients together well in a dry state. Make sure the mix is uniform in both color and texture, then add clean water and mix until the stucco is about the consistency of applesauce.
(Tip: You can boost the formula to three-fourths part hydrated lime if you want. Once it hardens, lime becomes a thin coat of limestone — and you know how durable limestone is.)
Lightly dampen the surface that will accept the stucco. Immediately after that, paint on a layer of cement paint. In the case at my church, the cement paint should have had some of the red dry pigment added to it. Cement paint is just a mixture of Portland cement and water mixed to the consistency of regular latex paint.
Brush the cement paint onto the surface; only work on as much surface area as you can cover with stucco within a minute or two. Keep the stucco damp for three days after it hardens. Do all these things, and you’ll have stucco that may last for 200 years or more.
Tim Carter has worked as a home-improvement professional for more than 30 years. To submit a question or to learn more, visit AsktheBuilder.com.