Water-Damaged Church Plaster? Fix the Outside First

Quick Answer: When the plaster inside a church stains, bubbles or falls off the wall, water is almost always getting in from outside. In churches the usual source is high on the building: the bell tower, the steeple, the gable walls and the window openings, where the masonry takes the worst weather and is the hardest to reach. The fix follows the same order every time. Find where the water is getting in, repair the masonry, roof or windows, give the wall time to dry, and then restore the plaster. Do it in that order and you only pay for the plaster once.

It usually starts small. A brown stain shows up high on the sanctuary wall, under the bell tower. The paint starts to bubble. A few months later somebody finds pieces of plaster on the floor after a Sunday service. The first call goes to a painter or a plasterer. That's the wrong first call.

Plaster almost never fails on its own. When interior plaster in a masonry church stains, blisters or crumbles, water is getting into the wall from somewhere, and most of the time that somewhere is outside, often a long way above where the stain shows up. Patch the plaster without stopping the water and you'll be patching it again.

We see this every year on churches across Iowa and the Midwest. Here's why churches get hit so hard, where the water is usually coming from, and the order of repairs that actually holds up.

Why Churches Get Hit Harder Than Most Buildings

A church isn't a typical masonry building, and the same features that make it beautiful also make it hard to keep dry.

• Height. Bell towers and steeples stand well above everything around them. They catch the wind and the wind-driven rain on every face, and they get no shelter from trees or neighboring buildings.
• Detail. Pinnacles, cornices, tracery, belfry openings and decorative brickwork add far more edges and joints than a plain wall. Every joint is a place for water to get in.
• Thick, solid walls. Many older churches are built with thick, solid masonry walls, and the plaster inside is often applied right to the masonry. There's no cavity to catch water on its way through. When the wall gets wet, the plaster shows it.
• Old, soft materials. Older churches were usually built with lime mortar and lime plaster. Both are meant to breathe and move with the building. They do that well when they're maintained, and they wear out when they aren't.
• Hard-to-reach maintenance. The parts of a church that take the most weather are the parts nobody can see up close. A bell tower can go years between inspections because getting up there takes equipment.

What Water Damage Looks Like on Plaster

Water leaves a trail. If you know what to look for, the wall will tell you a lot before anyone opens it up.

• Stains. Brown or yellow rings, often with a hard edge where the water dried. Rings inside rings usually mean the leak has happened more than once.
• Bubbling or peeling paint. Moisture behind the paint pushes it off the wall.
• White, crusty or fuzzy deposits. These are salts. Water picks them up from the masonry and leaves them behind on the surface when it dries.
• Soft or powdery plaster. Plaster that crumbles when you press on it has been wet too many times.
• Hollow or bulging spots. If a section sounds hollow when you tap it, the plaster has let go of the wall behind it.

A stain by itself doesn't tell you how bad things are inside the wall. It tells you water got there. On a church, where the damage shows up inside is often a clue to where it starts outside. Damage high on the walls and ceilings near the tower usually points up.

Where the Water Is Getting In

Interior damage rarely sits right behind the leak. Water travels through masonry, along the tops of beams and down the inside of walls before it shows up on plaster. On churches, these are the usual sources.

The bell tower and steeple

The tower is the most exposed masonry on the building, so it's usually the first place we look. Mortar joints on a tower wear out faster than the rest of the church. Belfry openings and louvers let in wind-driven rain. The caps, copings and cornices at the top let water straight down into the masonry when their joints open up. Hidden iron anchors and ties rust, expand and crack the masonry around them. Our article on bell towers and steeples covers the warning signs.

On one church we looked at this spring, the parish first noticed the problem as broken plaster and moisture on the interior walls. Outside, the mortar joints on the bell tower were so broadly deteriorated that the tower needed full repointing, not spot repairs. That's common. By the time plaster is falling inside, the masonry above it has usually been letting water in for years.

Mortar joints on tall walls

Mortar is the part of a masonry wall that's meant to wear out. When joints crack, recess or wash out, rain gets into the wall on every storm. On a tall gable wall facing the prevailing weather, that adds up to a lot of water. Repointing the joints with a compatible mortar is often the single biggest fix. Our article on tuckpointing vs. repointing explains why matching the mortar to the building matters.

Windows and stained glass openings

Church windows are big, and there are a lot of them. Sealant around the frames dries out and cracks. Stone sills tip the wrong way or lose their joints. Wood frames rot. Steel lintels over the openings rust and crack the masonry around them. Damage that shows up under or beside a window usually comes from the window. Our article on warning signs of lintel failure covers what to look for.

Parapets, copings and roof flashing

Where a gable wall rises above the roof, or where the roof meets the tower, open joints and failed flashing send water straight down into the masonry. Stains near ceilings and at the tops of walls often start here.

Gutters and downspouts

A clogged gutter or a downspout that dumps against the wall soaks the same spot every time it rains. It's a cheap fix, and it gets missed all the time.

The Hard Part on a Church: Getting to the Work

On most church projects the masonry repair itself isn't the hardest part. Getting to it is.

A bell tower can rise well over a hundred feet. Reaching it safely might mean a large boom lift, scaffolding built up the tower, or a mast climber. Which one works depends on things that have nothing to do with the masonry. Mature trees and landscaping around the church limit where equipment can sit. Slopes, steps and sidewalks get in the way. The ground has to hold the weight of a lift, and older churches sometimes have basements, crypts or tunnels under the spot you'd want to set up on. On that same church, the repair areas themselves weren't large. The mature landscaping around the building was what made the access demanding, and the price reflected it.

That's why access is usually the biggest single factor in what masonry work costs, and why any price given before someone has looked at the building is a guess. We break that down in How Much Does Commercial Tuckpointing Cost?

Churches also have a calendar. The work has to fit around Masses and services, weddings and funerals, and the busy weeks before Christmas and Easter. A good contractor plans the access, the noise and the parking around your schedule, not the other way around.

Finding the Source Before Anyone Fixes Anything

Finding the leak is detective work, not guesswork.

It starts inside. Map where the damage is and how it's shaped. Then go outside and look at the same spot from the other side of the wall, and above it. Check the mortar joints, the tower, the copings, the flashing, the window perimeters and the downspouts. A stain on the sanctuary wall can start at the belfry, two or three stories up.

On a church, a drone survey is often the fastest way to see the tower and the high walls up close before anyone pays for a lift. When the source still isn't clear, the next step is testing, like wetting one section of the exterior at a time to see where water shows up inside. The goal is to know what's causing the problem before anyone spends money fixing it. We walk through that process in Anatomy of a Masonry Investigation.

Fix the Outside, Then Let the Wall Dry

Once the leak is stopped, the wall still has to dry out. Church walls are thick, and they hold a lot of water. They give it up slowly, and slower still in cold weather.

As the wall dries, salts keep moving to the surface. If you plaster and paint too soon, those salts push the new finish right back off the wall, and it looks like the leak never got fixed. Patience here saves you a second repair.

How long it takes depends on the wall, how wet it got and the time of year. That's a call to make on the building, not by the calendar. Many parishes plan the exterior repairs for the warmer months and schedule the interior plaster once the wall has had time to dry.

Restoring the Plaster the Right Way

When the wall is ready, the plaster repair should match what's already there.

Most older churches have lime plaster. Lime is softer than modern materials and lets moisture move through it and out of the wall. Patching lime plaster with a harder material, or covering the wall with a paint that doesn't breathe, can trap moisture and start the cycle over. On historic interiors, look for a plasterer with real lime experience.

Ripping it all out and hanging drywall can look like the easy answer. In a church it usually means losing original material and character, and it doesn't fix the reason the plaster failed in the first place. On church and historic projects, we often work alongside Prestige Coatings & Color, a lime plaster company in Durant, Iowa. We fix the masonry, and they restore the plaster. On the Brigham and Mary Ann Young Home in Nauvoo, Illinois, they installed the lime plaster over the masonry we restored and rebuilt. Andrew Thornton explains why old plaster is often worth saving in our vendor spotlight on Prestige.

Planning It With Your Parish

Church repairs are usually paid for by a building fund, a capital campaign or a few years of budgets. That's fine, as long as the work is planned as a whole and done in the right order.

Start with one plan for the whole building, not a fix for whatever is leaking this year. Then phase it around the money. At St. Paul Lutheran Church in Clinton, we priced the work elevation by elevation, so the congregation could see the whole job and approve it in stages: the north wall first, then the east, then the west and south walls and the bell tower.

Put the work that stops the water first. Every phase should leave the building closed up against the weather, and the interior plaster should come after the exterior work that's protecting it.

And don't wait too long. Towers don't usually fail all at once, but when they do it's an emergency. At St. Michael Catholic Church, the parish called us after its bell tower had collapsed, and we rebuilt it. Catching the problem while it's still a stain on the wall is a lot less expensive than rebuilding a tower.

Why the Order Matters

Doing the work out of order is how parishes end up paying for the same repair twice. New plaster over a wall that's still leaking will fail. New plaster over a wall that's still wet will fail too, just more slowly.

The right order is simple: find the cause, fix the outside, let the wall dry, then restore the inside. It takes a little more patience up front, and it's the version of the job you only pay for once.

If you're seeing stains, bubbling or crumbling plaster in your church, start with the outside. Request an assessment and we'll walk the building with you, look at the tower and the high walls, find where the water is getting in, and give you a scope and budget your committee can plan against. You can see more of our church work on our religious buildings page.