Masonry Restoration Of The Minnesota State Capitol

SEALANT, WATERPROOFING & RESTORATION INSTITUTE WINTER 2021 43.1Masonry Restorationof the MinnesotaState Capitol Building

COVER STORYMasonry Restoration of theMinnesota State Capitol BuildingBY TIM MILLER243.1 WINTER 2021

AWWW.SWRIONLINE.ORGdvanced Masonry Restoration had the honor and privilegeof being selected as the interior and exterior masonryrestoration contractor for the four year comprehensiverenovation of the Minnesota State Capitol beginning in 2013.3

The current state Capitol building, the third inMinnesota’s history, was completed in 1905. The first oneburned down, the second one was almost immediatelyoutgrown. The current capitol had a 12 year constructionschedule at a cost of 12.5 million, approximately 110million today. Considering the state was only 37 years oldat the time of the groundbreaking, it was an ambitiousproject. The Capitol contains the second largest selfsupported dome in the world after St. Peter’s Basilica inRome. The dome has three layers: the outer layer is a selfsupporting dome made of Georgia marble blocks restingupon their own weight. Hidden inside is a brick and steelcone that supports the lantern and gold ball at the top ofthe dome. Below that is the decorative masonry domevisible by looking up from the rotunda. Local architectCass Gilbert was the designer, and this project gave him anational reputation which eventually led to his selectionas designer of the US Supreme Court building.Trial areas selected incorporated allarchitectural elements on the Capitol.The exterior of the Minnesota State Capitol is made of whiteGeorgia marble and St. Cloud granite. Gilbert insistedon using Georgia white marble, saying that the use of adarker color would make it lookgloomy and forbidding. He wonout over those who objected thatMinnesotans would lose stonecutting and carving jobs if stonefrom out-of-state was used. As acompromise, the general contractor,Butler-Ryan Co., leased the Georgiaquarry and shipped the rough-cutmarble to St. Paul to allow localThe stone team consisted of thefollowing companies:Architects:HGAEngineer:Wiss, Janney, ElstnerConstruction Manager:JE DunnStone Restoration:Advanced Masonry Restoration, Inc.Stone Installation:Mark 1Supplier:PolycorCarving:Traditional Cut StoneField Measurement:Twin City Tile & MarbleTypical condition of backup masonry.443.1 WINTER 2021

GOALS: Finding the right balance of maintaining historicfabric and loss of integrity. Finding the acceptable minimum effort requiredto protect the building. Assessing to what extent modification orreshaping of historic material was appropriate. Ascertaining what would be an acceptable levelof convincing detail. Deciding when replacement is necessary oracceptable. Deciding if new work should purposely bedistinguishable from original, if so how. Deciding what could be done to extend thelongevity of the marble.craftsmen to do the work on site. Gilbert also specifiedMinnesota-quarried granite for the ground floor level,steps, and terraces, and sandstone and limestone for thefoundation and interior walls to fully represent the variousstones from the state.Various exterior masonry repair or projects began on thebuilding starting in the 1930’s and continued over thedecades. However none of these were ever fully fundedand deterioration and decay began to build exponentially.Finally in 2011 it was recognized that the life safetyissues that became undeniable with releasing stone,coupled with severe aging infrastructure issues, were notgoing to improve and a 22-person Capitol PreservationCommission was formed. This led to appropriationsfunding of 310 million beginningin 2013. Virtually every aspect of thebuilding was replaced, rebuilt orrenovated: HVAC replaced and rerouted, building envelope restored,roof replaced, code compliance broughtup to date, modernization of electricalsystems, artwork cleaned and restored;all this was accomplished whilepreserving the original appearance. Inthis article we will focus on the masonryrestoration aspects of the project.companies were not based in Minnesota, there was aproject-wide focus on utilizing in-state workers andartisans as much as possible.The primary objectives of the stone team were life safety,restoring the building integrity, water management andbuilding stewardship. Stone repair trials began Octoberof 2012. Trial areas were established to demonstrate theconstructability of various techniques, effectiveness ofthe suggested repairs and the visual appearance of theoverall result.The exterior architectural features that were affectedincluded displaced ashlar stone units, column capitalelements and balustrade components. As with allrestoration projects of this magnitude, integrity assessmentbased on visual observation was not always viable, sominimally destructive openings were made mainly toassist with peephole camera insertion at and around thedamaged units.Trial areas showed long term water infiltration from above,almost exclusively from poor maintenance of skywardfacing joints. The backup masonry was saturated and was unable toever completely dry out due to lack of an engineereddrainage system. The brick and stone showed heavy evidence of freeze/thaw damage. Minnesota winters often have extremetemperature swings, from above freezing to below zero inas little as 18 hours. As water expands approximately 10%upon freezing, this wreaks havoc with saturated masonry.Replacement stone was sourced fromGeorgia Marble in Pickens County, GA,the original quarry.While bid pricing was a factor, giventhe historical significance, publicawareness and difficulty of this project,all members of the stone team wereultimately selected based on experienceand knowledge. While some of theseWWW.SWRIONLINE.ORGExamples of deterioration on the building exterior.5

Vein cracking at cornice. Freeze/thaw damage expansion also caused severalunits to shift outward. Stone anchors were corroded and for the most partineffectual. Larger stone units, especially at the cornice, showedheavy vein erosion in the marble and diagonal cracking.Repairs were made on a case-by-case basis dependingon the condition of the stone. In some cases Dutchmanrepairs were opted for. Displaced units that were 100%undamaged were removed and salvaged. If required, thebackup was repointed or replaced and the stone reinstalledwith new stainless steel anchors. Unsalvageable units werereplaced with new units. Mark 1 Restoration handled stonereplacement such as this throughout the project. Chipped,surface cracked or spalled but otherwise structurally soundunits were removed and re-anchored and then repaired byAMR. Profiles were patched and carved also utilizing Jahns.6There was no pre-approved standard color, every areathat was patched required a different blend of colorsto match both the base and the marble veining. Thehighly carved elements such as those on the pilasters andcapitals demonstrated the most severe damage and loss ofdetail. It was determined that these projecting units havelarger surface areas that are more exposed to damagingclimate factors. In addition, ornately carved figures aremore vulnerable to distress than are flat surfaces. Alsothe original carving practices utilized hand chiselsand hammers; unfortunately this method exacerbatesnaturally occurring micro-fractures, leaving the stone morevulnerable to water infiltration.Ultimately every piece of stone on the building was touched,and 4,000 pieces of stone were replaced. As the scope grew,the original single fabricator receiving stone from the quarrywas expanded to a total of five. Some blocks were sentto Toronto and Italy for carving, to assist the four mastercarvers who were onsite for the project duration.43.1 WINTER 2021

Eroded element, base patching started.“Ultimately every piece of stone onthe building was touched, and 4,000pieces of stone were replaced.”Before and after replacement elementswere put into place.Specially carved pieces being installed.WWW.SWRIONLINE.ORG7

Eroded element, patched to match profile.One of the larger unforeseen repairs that arose was thereplacement of the 15,000 square foot stairs fronting theCapitol. Since they were repaired in the 1990’s it wasassumed they were sound, however shifting treads ledto the discovery that the limestone foundation has lostits bearing capacity. The stair system wasdismantled and rebuilt with the original treadssalvaged and reinstalled.the tiles. This was all done through trial and error andmaximized by their knowledge from previous projects, aswell as their artistic abilities. Sarah Arkeh, AMR’s MasterStonemason for the project, visited pet stores, hobbystores and elsewhere attempting to find items that wouldThe final scope of work on the interior masonrycomponents ended up being much moreextensive than originally planned, especially asceilings and walls covered over in the last 100years were exposed. AMR’s staff of masonsrestored and repaired Kasota limestone, severaltypes of marble, terrazzo, Guastavino tile andblack granite. Cracked stone was patched,missing pieces recreated, old bad patchesreplaced, stone joints regrouted and stonesurfaces refinished.There was extensive penetration of theGuastavino tile by ceiling grid supporthangers, as well as numerous missing tiles.Our journeywomen had to develop a patchingmortar that would hold, and then match theexisting color of the tile. They then neededto find or fabricate the tools needed to matchthe notched profile, as well as develop thetechniques necessary to match the profile of8Damaged tile, base patching started.43.1 WINTER 2021

Front stairs of the Capitol.match the necessary grooving for the tile. Of all thingsshe eventually found an older style flat edged paperclip that worked perfectly. All of this time and effortculminated with what we refer to as the centerpiece ofAMR’s contribution to the project, the renovation of theGuastavino tile ceiling in the East Porte cochere of theCapitol that had been hidden for years. Edison Thinfill55 was used on the Guastavino tiles, coated with a terracotta glaze to match the existing finish.Color and texture matches had to be perfect on everysingle patch on every single material type. After marblepatching, potassium silicate of various hues was uses tomatch the veining.No standard colors were acceptable, every patch wascustom colored to blend perfectly. Every patch had tomatch the texture of the surface it was applied to and thencolorized to match the surrounding stone and patina.Profile matching in progress.WWW.SWRIONLINE.ORGAfter installing every one of the over 1,200 repairs on theceiling, floors and walls, the repair locations were markedon the plans for later architectural inspections. Incredibly,9

Matched profile.“No standard colors were acceptable,every patch was custom colored toblend perfectly.”Cracked marble.Completed patch, profiled and coloredto emulate natural veining.94% of the patches could not be found without the aid ofthe person who repaired it. Documentation of the locationswas subsequently turned over to the State of Minnesota forarchival purposes, cementing AMR’s place as a part of ourstate’s history.10Interior marble base patch.Completed patch.There is a reason why the cover page of AMR’s websitefeatures the State Capitol project. This prestigious projectis the culmination of all of the blood, sweat and tears wehave spent in building our company over the last 25 years.We employ an average of 80 union masons every year, and43.1 WINTER 2021