Preservation basics wood-stone-brick by richaven
•
4 recomendaciones•982 vistas
Brian Rich gave this presentation at the Historic Seattle Building Renovation Fair in 2012.
Recomendados
Más contenido relacionado
Destacado
Destacado (16)
Más de Brian Rich
Más de Brian Rich (18)
Último
Último (20)
Preservation basics wood-stone-brick by richaven
- 1. www.richaven.com SUSTAINABLEPRESERVATIONARCHITECTURE&CONSTRUCTIONMANAGEMENT206.909.9866 Historic Seattle 2013 Building Renovation Fair WOOD, STONE & BRICK: PRESERVATION BASICS
- 3. www.richaven.com SUSTAINABLEPRESERVATIONARCHITECTURE&CONSTRUCTIONMANAGEMENT206.909.9866 SOFTWOODS: • Temperate Climates • Distinct growth rings (more differences between temperate seasons) • Evergreen • Needles HARDWOODS: • Tropical Climates • Less distinct growth rings (fewer differences between tropical seasons) • Deciduous • Leaves
- 5. www.richaven.com SUSTAINABLEPRESERVATIONARCHITECTURE&CONSTRUCTIONMANAGEMENT206.909.9866 DIFFERENT TERMS FOR WOOD DEFECTS Fork Wire Decay Crack Crook Warp Twist Bow Check Split Burl Bird peck Blue stain Dead knot Shake Holes Bumps Bulges Conk Sweep Cup
- 7. www.richaven.com SUSTAINABLEPRESERVATIONARCHITECTURE&CONSTRUCTIONMANAGEMENT206.909.9866 – Eyeballs! – Ice pick or sharp knife – Thermography (thermal imaging) – Density drilling – Radiography – Infra-red imaging – LoadTesting – in situ Non-DestructiveTesting
- 8. www.richaven.com SUSTAINABLEPRESERVATIONARCHITECTURE&CONSTRUCTIONMANAGEMENT206.909.9866 RepairTechniques • Wood Fillers – Latex (Acrylic), Polyurethane, Epoxy • Wood Consolidants – Polyurethane • Failure ofWood Repair Materials – Bond strength – Repair material strength/flexibility – Substrate preparation – Discoloration
- 9. www.richaven.com SUSTAINABLEPRESERVATIONARCHITECTURE&CONSTRUCTIONMANAGEMENT206.909.9866 Mineralogy Silicate vs. Carbonate Minerals • Two basic chemical compositions of all stone • Understanding the mineralogy of the stone is critical to • Understanding soiling problems • Proper cleaning of the material VS
- 10. www.richaven.com SUSTAINABLEPRESERVATIONARCHITECTURE&CONSTRUCTIONMANAGEMENT206.909.9866 Mineralogy Silicate Stone With Increased Iron & Magnesium • Chemically weaker stone • Mechanically weaker stone • Darker colors Silicate rocks include: • Quartz • Agates • Feldspars • Chlorite • Amphibole • Pyroxene • Olivine
- 11. www.richaven.com SUSTAINABLEPRESERVATIONARCHITECTURE&CONSTRUCTIONMANAGEMENT206.909.9866 Mineralogy Non-Silicate (Carbonate) Rocks Include: • Gypsum • Aragonite • Dolomites • Calcites • Pyrites • Hematites Carbonate Minerals • Can be detected by dropping acid on it and seeing if it reacts • CaCO3 + HCl -> CA 2+ & CO2
- 12. www.richaven.com SUSTAINABLEPRESERVATIONARCHITECTURE&CONSTRUCTIONMANAGEMENT206.909.9866 Rock Identification Overall Scheme for Rock Identification Lighter Darker
- 13. www.richaven.com SUSTAINABLEPRESERVATIONARCHITECTURE&CONSTRUCTIONMANAGEMENT206.909.9866 Types of Stone Deterioration Microbiological Macrobiological ACID RAIN GYPSUMCRUSTING DRY DEPOSITION SALTCRYSTALLIZATION FREEZE/THAWCYCLING HYGRIC SWELLINGBIOLOGICAL EFFECTS
- 16. www.richaven.com SUSTAINABLEPRESERVATIONARCHITECTURE&CONSTRUCTIONMANAGEMENT206.909.9866 Chemical Cleaning Aesthetic concerns – can alter color of stone Material Science concerns – can remove excessive amounts of the stone or add materials that lead to later deterioration Very fast cleaning method – dwell time is critical and must be carefully controlled Difficult to isolate areas to be cleaned In all cases, salts must be cleaned out after neutralizing wash RINSE, RINSE, RINSE!
- 22. www.richaven.com SUSTAINABLEPRESERVATIONARCHITECTURE&CONSTRUCTIONMANAGEMENT206.909.9866 Compensating for Loss of Material Two basic methods: Replacement • In-kind • Near in-kind • In pre-cast imitation Repair • Surface • Composite (plastic)
- 23. www.richaven.com SUSTAINABLEPRESERVATIONARCHITECTURE&CONSTRUCTIONMANAGEMENT206.909.9866 Brick & Clay Masonry
- 26. www.richaven.com SUSTAINABLEPRESERVATIONARCHITECTURE&CONSTRUCTIONMANAGEMENT206.909.9866 Or you can make brick like this…
- 30. www.richaven.com SUSTAINABLEPRESERVATIONARCHITECTURE&CONSTRUCTIONMANAGEMENT206.909.9866 Brick Repair Rake out joints Clean head joints Wash out loose material Fill joints with mortar Tool joints Brush off excess mortar
Notas del editor
- This is more typical of a softwood tree, such as hem-fir or douglas fir.Review different parts of tree, compare in three picturesBarkSapwoodHeartwoodGrowth RingsPithCritical to understand that wood is a natural material, not man-made, and thus inherently has defects.These defects can be considered beautiful or ugly – beauty is in the eye of the beholder
- Log to LumberDifferent cuts of wood affect:How it will perform over timeHow it will react to moisture
- Modes of DeteriorationCritical to understand the nature of wood to understand the modes of deteriorationCritical to understand the modes of deterioration to determine methods of repairIs the deterioration still active?Is it important to leave the deteriorated material in the building?Additional Questions to ask include:Can deterioration be arrested?Can it be inspected regularly?Will it be maintained?Is the material structurally or historically significant?Modes of deterioration include:Structural Failure (Tension, compression failure)Often seen as a fracture or splitting, it is a failure of the wood fibersWeatheringMoisture content changes: Warping, checking, splitting, twistingFailed alterationsRotBiological deteriorationMold, mildew, fungiHerbivorous failure Xylophagy: The eating of wood as is done by insects - Powder post beetles, carpenter ants, etc.
- Repair techniquesStructuralFailing in tension: Reduce loads and supplement with tension rods or platesFailing in Compression: Reduce loads and/or increase wood cross sectionMoistureStop the water intrusion and dry out the wood!Drill and insert Borate rods – water activatedBiologicalArrest biological growth firstReinforce or repair materials in kind, if possibleCritterStop the critters!Powder post beetles - characterized by a 1 to 2 mm holefill holes and if new ones appear, it’s activelook for frass at holesCarpenter Antslarge black ants that are frequently visibleThey eat the soft spring growth wood between winter growth ringsFirePut the fire out…Measure depth of char - pillowing may protect core of woodmill and re-use wood in another part of the buildingWood Fillers: Wax putty, Latex, Polyurethane, EpoxyEpoxy gains strength through filler material (usually wood material). Marine epoxy uses fiberglass reinforcement – not appropriate for wood repairsConventional epoxy consolidant materials filled with air, micro-balloons, and fillers greatly reduce the flexibility and peel strengthEpoxy materials sensitive to temperature at time of application. Thinner epoxy cures slower than thicker epoxy. The colder epoxy gets, the longer it takes to cure. Epoxies can also shrink, depending on product.Latex and Polyurethane – subject to UV degradation and hard/brittle materials.Bondo or generically known as polyester based auto body repair materials – brittle repair material meant for metal surfaces. Will not bond well with wood.Failure of wood patching materials: Bonding strength failure, Poor surface preparation, and Failure of repair material possible.
- Acid RainAcid dissolves carbonate rockGypsum CrustingBlack from fly ash (not calcium)May be on top of original surface or in place of original surfaceCan merge with surface and then break offBe careful to select the correct acid washDry depositionDissolved material from acid rain is re-deposited as gypsum crusts elsewhere on the rock on top of original surfaceUsually found in protected parts of the rock where rain will not wash away the gypsumGypsum can be re-absorbed back into surface of rock and will not come outSalt CrystallizationSalts are dissolved from within the rock, transit to the surface and then deposited when water evaporates. Known as efflorescence5 common salts are:CaCO3 – lime not hydrated enoughCaSO42-H2o – gypsumNaS04 – Sodium Sulfate can form at poorly rinsed alkaline washesNaNO4 – Decaying organic materialKNO3 – gunpowder stored in buildingFreezing waterFreeze thaw cycling results in spallingHygric swellingRock absorbs water and can then be subject to freeze/thaw cycles, salt crystallization, or other thermal effectsClay in stone helps swellingEgyptian Limestone (below, after 3 cycles)Biological Effects (Bio-deterioration)Plant life creates complex acids to dissolve and suck minerals out of rockPlant life grows into crevicesLight, Nutritive input, temperature, and water affect bio-deteriorationBiodeterioration diagram Bacteria, Algae, Fungae – no mechanical effects – mostly chemical from metabolism Lichens – symbiotic relationship with algae, tear away surface when they shrink, very difficult to clean Mosses & Higher plants – mechanical deterioration forcing rock cracks widerThermal EffectsExpansion and contraction creates weak planes in rockWater is an AID to soiling in Silicate rocksWater PREVENTS soiling in Carbonate rocks
- Intermittent water spraying does least damage to delicate stoneIntervelometers – photo equipment timer can turn water on or off for a few seconds throughout the dayIrrigation sprinkler timers – not as sensitiveControlling the length of cleaning timing is criticalTest water for contaminants and acidity5 micron filters required to remove iron in waterIf stone is delicate, you may not want to try and wash out gypsum crusting that has been reabsorbedPartial CleaningNot really possible with water except for reabsorbed gypsumCold water is better for removing gypsumWarm water is better for emulsifying hydrocarbons
- Advantages of Chemical CleaningSpeed of executionDisadvantages of Chemical CleaningUsually requires pressure washing for adequate removal of chemical residuesUsually requires acids either as a cleaning agent or neutralizing agent that can attack the substrateWith speed of execution comes limited controlCan leave residues that lead to efflorescence and possibly salt damageCan alter color of stones by changing oxidation state of iron oxide compoundsCan deposit fine white particles on surface
- Abrasive Cleaning SummaryCan be used on different stone (and other masonry) types in juxtapositionCannot not be easily used on fragile stone surfacesContainment is often a problemCan be difficult to achieve uniform cleaning at timesDoes not remove subsurface materialsCan easily be used in conjunction with other techniquesRequires trained operatorsDry techniques eliminate risk of stainingWet techniques can mobilize saltsSoft pointing may be damaged during cleaningResoiling rates may be higher than for other techniquesLocalized cleaning can easily be carried outCleaning is non seasonalCannot remove sub-surface soiling (migration of gypsum into stone)Façade Gommage or ThomannHanryMedium glass beads or aluminum oxide Size 15-90 micronsShape round-to-angularPressure 35-50 psiDelivery airWorking Distance approximately 10 inches perpendicular to surfaceContainment can be difficult on non-flat surfaces (vacuum)No competitive bidding – only one contractor can provide servicesArmexMedium sodium bicarbonateSize 60-600 micronsShape angularPressure 40-50 psiDelivery air and waterWorking Distance approximately 12 inches 60 degrees to surfaceNot as effective as other abrasive techniquesMay leave sodium bicarbonate residue (results in sodium sulfate salts)Jos QuintecMedium dolomiteSize 60-600 microns with 75% between 70 & 270 micronsShape round-to-angularPressure 30 psiDelivery air and waterWorking Distance approximately 12 inches, vortex yields 45 degree angle to surfaceContainment is a major problemCan be used by any trained contractor – competitive bidding easyMultiple nozzle sizes and shapes
- AdvantagesNot a particle so it can be used on very delicate stoneOnly works on dark soiling on light colored stonedark absorbs laser energyif used on dark stone, it will damage the stonePhysically the most gentle of all cleaning methodsPartial cleaning possible – control over small areasLaser cleaning leaves “patina” of gypsum or oxalatesDisadvantagesPrimary risk is yellowing of the stone Sources include patina inherent to object, alteration of structure of the marble, transformation of iron minerals or organics in soiling.Slow – lasers do not cover a large areaCan only be used on a narrow range of stone typesExpensiveDoes not remove subsurface gypsumRequires a skilled Operator
- What Types of Stone Benefit from Consolidation?LimestoneMarbleSandstoneCharacteristics of the ideal ConsolidantLow VOC is not commonThere is no such thing as “reversible” – removal damages stoneConsolidant can be applied to all substrates, but may not work equally wellTypes of ConsolidantsEpoxies are not used much anymoreToxicity of barium is a problem in environmentCalcium hydroxide = lime method
- Stone Adhesives include:AcrylicsMethyl methacrylate (MMA)Acryloid B-72 (ethyl methacrylate and methyl acrylate co-polymerAcryloid B-48N (methyl methacrylate co-polymer)Addition of Poly Vinyl Acetates (PVAC)EpoxiesManufacturers include Akemi and SikadurPolyestersManufacturers include Akemi and SebralitMechanical aids to reconstructing stone include:StaplesDowelsDrilled in anchorsCarbon Fiber ReinforcementStrong-back support of masonryTeflonNylonBrassAluminumConsiderations in Pinning MaterialsMaterial Properties (strengths and weaknesses)Installation techniquesAesthetic effectsCoefficients of Expansion (stone versus pins)Titanium = Limestone & MarbleSteel = Concrete and cement mortarsAluminum and organic resins are higher than stone, typicallypH ranges affect steel corrosionLow pH = more acidic = more corrosion
- Technical Considerations In Choosing A Compensation Method:Is it reversible?Does it damage the original?Does it require removal of the original materials?Equal to or less than the strength of the original materials?Is it easy to work?Is it stable?Is it transferable to all cases?Is it cost effective?Does it satisfy aesthetic requirements?Additional ConsiderationsWhat is the scale of the loss?What is the environment of the loss?What are the available resources (materials, craftsman, etc)?Additional outdoor considerations include:Durability of the methodGood weathering propertiesNo salt contentSame properties as stone (thermal expansion, water absorption, exchange, strength, etc.)Disadvantages of Replacement Option:May not be a fulfilling aestheticUsually requires removal of the original materialsNot a simple processCan be expensive
- Bricks in the Pacific Northwest originally came from the midwest or east coast.If you have old brick, it may have been ballast in one of the trading ships that came to this region.
- Keys to commercial process: consistency of material used to make brick high temperature firing creates fire skin
- Water is you enemy!Fireskin is a natural membrane that prevents absorption of water. Other people use paint….Mortar joins should be lower strength material than the brick to allow moisture to evaporate out.
- Brick is subject to many of the same deterioration methods that stone is subject to.There are two additional methods of deterioration:First, the mortar in the joints can erode away. This is good!It means the mortar is softer than the brick and is allowing moisture to escape.More importantly, it is protecting the brick from deteriorating as a sacrificial material.
- When mortar is harder than the brick, the brick begins to exfoliate due to water pressure behind the fireskinOnce the fireskin is gone, the inner water absorptive core of the brick is exposed and deteriorates more rapidly.Which is easier to replace, the mortar or the brick?
- Brick repair, conceptually, is relatively easy.Remove the brick or mortar and put new material in.In reality, this is complicated by aesthetic and size and strength considerations for the brickAnd, if trying to match mortar to an existing mortar, getting the right strength and color can be difficult