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The past wasn’t so long ago: how a WWI-era concrete building surprised us with itsconnection to the pastPosted on March 11, 2014

We were recently asked by a developer to look at a large open air shed they are turning into retail space belowand offices above. Since the project sought to use historic tax credit funding, they had many preservationentities to satisfy.

The developer wanted to sheath the building in glass, but otherwise leave much of the structure exposed. Theyneeded our help interpreting what is unique and important about the structure. Historic buildings are alwaystrying to tell us a story. While concrete structures are now ubiquitous, what makes this one unique?

On our first visit, the interior was inaccessible, but wewere drawn to the unique colorations on the mostlyweathered paint surfaces. When we returned to look atthe building again on a nice cloudy day, we could see thebeautiful formwork with the wood grain clearly visibleeven 20 feet up on the ceilings.

This very unusual structure looked like Greene & Greeneconstruction or a Japanesque post and beam structure,only this time it is constructed of concrete. Built in 1918when concrete construction was still developing theprocedures for large-scale construction, we are able to

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see how the forms were constructed. As in all architecture that preceded it, we had the evidence of materials,tool marks and joinery to tell us how the building was constructed.

Unlike today when modular formwork systems are bolted together and reused, every pieceof this structure was built in place by carpenters.

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The real beauty here was that they used boards that had left the imprint of their grain in the concrete. There areboth sash and circular saw marks visible.

Early black and white pictures were available to show conditions at the time of construction. We wondered whatwe might learn from them. In unison with looking back at the building itself, the answer was quite a lot. Weknow in the 19th century concrete was often poured at a rate of only a foot or two per day. But it is pretty clearfrom this site and how the forms are built, that they were doing continuous pours of the 16’ tall columns orentire floors all at once.

The pictures of the forms around the columns show a box made of boards with rangers (horizontal braces) toresist blowout from the extreme pressure on the forms (up to 600#/foot). Whereas by the 1930s the formwork

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would be made of ⅞” boards, these look to have been created of 1-¼” material. The column forms were reusedand thus most of them have much less grain visible. Form building at the time was complicated and expensive.Every effort was made to allow wood to be reused, whether attic sheathing, sub-flooring, or diagonal sheathing.

The boards were rough sawn. In the 1910s it was common to plane a single side toestablish a consistent board thickness. Occasionally we see where a board wasreversed leaving visible planer marks.

It was also common in concrete structures at this time that if the ceilings weregoing to be exposed, painted or oiled canvas was put on the upper side of theboards so they would have a smooth ceiling once the formwork wasremoved. Since this was meant to be a utilitarian building, they did not botherwith this step.

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The more we look, the more a building reveals how it was constructed.

We began to see two things: an imprint of every board used in the formwork andan early paint history. We had discovered basically three colors on the buildingand initially thought we would clean the surfaces, stabilize the original paints andthen infill paint to match where missing. But we noticed that almost everywhere –to one degree or another – one of the paints seemed to predominate over theothers and on some of the columns where we suspected forms had been reused,we noticed the surface was very sanded and that this color was blended aroundthe sand grains. This suggested something other than paint applied after the fact.

It was common in the late 19th and early 20th century to oil boards as a releaseagent. By the 1930s trades books reference the inadvisability of oiling boards as itleaves a stained and mottled surface. They comment that in the early days of

concrete formwork when boards were oiled that crews often took the forms off too early. But at least the mid-1920s, most trades manuals had concluded that taking forms off early was inadvisable. Instead, since concreteshrinks, just by waiting the forms would separate on their own when the concrete was cured enough to supportitself.

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We conducted an experiment by taking some boards with a pronounced grain, oiling them with linseed oil, andput mortar on the boards and let it set for about a week. Sure enough, the surface had a grayish tan coating on itonce the mortar was removed. So what appeared to be paint appears to have been another remnant of theoriginal construction process. The bases of the columns close to the perimeter were more yellow and faded outwhere the sunlight had hit them, but on the ceiling the color was more evenly gray. And on the top side of beamsyou are simply looking at gray concrete because it had never been in contact with formwork.

.After using a Recyclean to remove dirt and soot, we had three main colors toconsider. In the end, the tannish-gray (seen in the cleaned band) was selected forthe entire space as it most represented the appearance of the oiled formwork. Weopted to paint in matte casein so the wood grain would “read” accurately.

Coming back to interpretation, this is a perfect example of the technology of thattime with what was a relatively new method of building. However if we were to interpret the wooden formworkas important to the buildings story, we were presented with the challenge of nearly a hundred years worth ofindifferent patches and repairs to the concrete that completely obliterated the board patterns and graining. Andthe new configuration further complicated the plan by intending to partially enclose some of the upper openingsto fit smaller windows using concrete block. Both of these were aesthetic problems to overcome.

Our initial thoughts were to use paint to faux bois the concrete so even damaged areas would “read” as grainedboards. We also tried making silicone rubber molds so we could stamp graining on, but single dimensional lineswould not work given the many angles of daylight hitting the walls throughout the day. We eventually concludedthat we while we would use faux bois graining tools, they would be used to tool a cement slurry that we couldsand or put aggregate into match that particular location that we were graining.

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The Matching Process

A week was spent grinding down concrete patches to the plane of the surrounding wall using a diamond cupgrinder. Then we needed to recreate the joints between boards where missing. Finally we had every kind ofgrain from flat sawn to quartered with knots and every variation in between to figure out how to recreate mid-

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board to match what remained on either side. And then we had to figure out the timing of adding to thisgraining the necessary tool marks (circular saw and vertical sash saw marks, as well as planer marks).

It took some time to work out the timing, tooling, sequencing and sandedness of each surface – and I can’t saythe results were always completely successful. But now every visitor to the space is once again aware of thewooden formwork in every office as opposed to being confronted by the tremendous numbers of patches thatexisted when we started.

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The Resulting Appearance and its Place in the Building’s Story

How do you interpret and protect uniqueness? There are several stories here. Why preserve things? Why arethings from the past important? How do you learn to read their story or listen to them? It has to be amultifaceted undertaking: you have to reach out to the building as it offers up its secrets. You have to make aneffort.

Concrete is ubiquitous now, but was a new construction material in 1917. Concurrent with this project, we wereworking on another building constructed in the 1830s by one of Thomas Jefferson’s carpenters where solidtimbers make up the post and beam structure. Here, just 80 years later (a single lifetime), is the same post andbeam detail but the wood is no longer the structural material. It is now the form for a plastic material (concrete).

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It took us trying to put what we saw into the context of history or people and building technology, asking whywas it there. While reviewing archival sources, we considered what we have learned in the last 50 years of ourown work (I remember oiled formwork still existed for certain applications when I first started in the trades).And each time we went back to look at the building, we saw some things a little more clearly and also sawsomething else we had missed previously.

An important tool in understanding buildings is the taking of minute samples for chemical and microscopicanalysis. Too often in preservation, sampling is done just to check off a box. Instead, sampling must be part of aquestion.

The results of laboratory analysis can add to the story of what these things were, what has happened to themover their life, and to determine the cause of their current distress. We engaged and made friends with thisstructure so we could establish a meaningful story which would allow the building to be converted for modernuse with an important story of its earlier life remaining for appreciation. If you don’t ask the questionsbeforehand, you usually lose most of the evidence.

The unique timbers of the this building’s construction are gone (and that caliber of timber largely unobtainabletoday) but they are telegraphed to the present in the concrete.

With the beams now exposed within a modern interior, we have anunexpected result: the hard concrete becomes the softening componentand the tan-gray paint, created from reds and greens rather than blacksand whites, undulates in tone depending on daylight, shadow, andvarious temperatures of modern lighting to create a very pleasingappearance.

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For more information about casein paint on masonry, check out this post.

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