The Predominant Color for Historic Metal Roofs

In modern times there are a multitude of paint color options for standing seam metal roofs, but by and large the predominant color of these roofs in historic times was red.  

red metal roofs

Manufacturers, even in production and marketing today, refer to the most dominant color from historic times as “Tinner’s Red”. Today, we will take a look at a historic standing seam red roof.  We will talk about the following topics:

  1. Why was Red Such a Popular Color
  2. Causes of Paint Delamination and Deterioration 
red seam roof in capital hill
The picture of shows a large, red painted, historic standing seam roof in Capital Hill, Washington, DC.

Why was Red Such a Popular Color 

There are a few key reasons why standing seam metal roofs were often painted red on historic buildings in Washington DC.  Unpainted tin or iron roofing will eventually succumb to rust and corrosion from exposure to the elements. A coat of paint provides a protective barrier to slow this oxidative decay. Red iron oxide pigments were commonly used in anti-corrosive primers and paints.

color for historic metal roofs

Red isn’t a highly light color but white was difficult to produce in historic times and although red is a moderate light and moderately dark color, its much lighter than black.  Lighter color roofs reflect more solar radiation, helping reduce heat transfer into buildings beneath. In warmer southern climates like Washington DC’s, white or lighter roofs reduce the thermal load which affects interior living spaces.  But red, with a darker more absorbing tone, was better suited to northern regions to maximize heat retention.

standing seam ferrous
This picture shows a closer view of the surface of the standing seam ferrous metal alloy roofing material.

Compared to white or light roofs which easily show soot and dust buildup, red roofs help camouflage accumulated grime. The naturally darker red color does not show dirtying as obviously.  For a flat roots on buildings like historic rowhomes, where the flat roof is entirely out of the view of the public eye this characteristic has no particular benefit, but the color red was used extensively in other parts of the market which affected supply chains and availability related to production, even in places here like Washington D.C.

standing seam ferrous

Red iron oxide pigments were common and inexpensive. Basic red barn paint could easily coat roofs. Other pigments were costlier and harder to source locally. Red paint’s ubiquity made it the default choice.

The red color provided rust inhibiting, heat management, dirt masking, visually enhancing, and cost savings benefits that made sense for historic metal roofs in Washington DC and beyond. The tradition continues to an extent today more for aesthetics than original functional reasons.

rust inhibiting red metal roof

Causes of Paint Delamination and Deterioration

When properly maintained, these ferrous tin alloy roofs can last for decades. However, when the protective coats of finish paint deteriorates, the underlying metal becomes exposed and vulnerable to oxidative deterioration.  Understanding common physical and chemical mechanisms of coating delamination and failure can help guide proper preservation methodologies.

Metal roofs expand and contract through daily heating and cooling cycles. Over years, this results in stress fatigue in the metal panels coatings. If the paint surface lacks elasticity, over time, and adhesion to accommodate the cyclic movements, cracking and peeling away from the metal substrate occurs. Modern paints have much better performance characteristics to maintain elasticity, but ultraviolet rays inevitably weaken even the best liquid applied material’s performance qualities.  Once paint layers separate and expose unprotected metal, water infiltration promotes corrosion.

causes of paint damage red metal roofs

A more insidious driver of the failure of metals happens when water becomes trapped between the painted metal as delamination begins. Here on our blog, we often attempt to explain one of the principle concerns about upkeep and duration of roofing materials, the non-linearity of deterioration. This concept basically means that as materials begin to deteriorate, they most often will continue to deteriorate but at an increase in rate for this is a real world example of how deterioration increases at an increasing rate, as paint becomes to delaminate, there will be a space between the peeling paint and the underlying substrate metal as rains and precipitation naturally continue water will become trapped in that interstitial space and cause much faster and higher amounts of deterioration through oxidation which will lead to pinholing, rust that actually amounts to holes through the roof. 

knife vs metal roof
Here in this picture, a pocket knife is laid on top of the roof surface to show the comparative scale reference.

Without an escape path, hydrostatic pressure builds until pushing up paint from the surface. This is especially problematic at joints or seam connections. Proper sealing is essential to prevent moisture ingress and allow drainage.

Incompatibilities between interactive paint reapplications also cause delamination issues. Applying a new paint, as required upkeep and maintenance, without proper surface preparation prevents bonding to the previous layers, resulting in easy peeling and splitting between layers. Old layers, often, must be removed for the new coating to adhere properly to the metal through mechanical and chemical bonding.

electrolysis accelerated oxidation on metal roof
Electrolysis, and associated accelerated oxidation can occur where dissimilar metals are in contact with the surface of a roof.  Here, a lazy past contractor left a metal bucket sitting on the roof surface.

Additionally, surface pollution like accumulated soot or metal oxides inhibit paint adhesion. Cleaning to bare metal promotes bonding of the fresh coating, but this is a tedious and dangerously precarious process on thin metals.  In most cases, its important to use a very experienced roofing contractor.  Proper priming immediately after cleaning helps guard against re-oxidation. Abrasion of the painted surface from weathering or excessive foot traffic also reduces adhesion and requires cleaning and repriming.

Without the protection of sound coating applications, ferrous roof panels experience red rust oxidation, compromising the integrity of the metal over time. The rust itself accelerates damage through expansion differences with the base metal, causing stresses and cracks. Maintaining paint through preventative maintenance and addressing failure early on avoids irreversible metal damage.

In summary, paint delamination on historic metal roofs stems from thermal stress fatigue, moisture ingress, incompatibility between layers, surface contamination, and uncorrected abrasion. Staying vigilant through regular inspection and promptly addressing any coating wear or damage ensures the longevity of historic ferrous roofing. Proper painting techniques coupled with surface preparation and repairs preserve functioning historic architectural features.

For effective low slope and mansard roof care in Washington, DC, chose a contractor like Dupont Roofing who has a passion for historical methodologies, waterproofing, and building science. Roofs safeguard both historic and modern buildings, which are significant investments. We urge clients and readers to prioritize quality construction, building upkeep, and consider building a connection with us. Explore our blog for more insights. If you have questions about your Washington, DC building’s roof, reach out through our webform – we’re here to help.

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