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Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. T YPES OF M ASONRY W ALLS 10 Masonry Wall Construction Slide 2 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Composite Masonry Walls Multiwythe Outer wythe of stone, face brick, or other durable masonry material Inner wythes of less expensive CMU or clay units which do not require the same level of durability or finish appearance Solid--no internal cavity Space between wythes is filled with mortar Wythes are bonded with: Header units (in traditional construction) Metal ties or reinforcing (right) Most commonly associated with traditional or historic masonry wall construction T YPES OF M ASONRY W ALLS Slide 3 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Masonry Cavity Walls Greater resistance to water penetration than solid or composite walls Multiwythe A continuous air space between wythes acts as an internal drainage plane. Water that penetrates the outer wythe runs down the cavity and then is drained back to the exterior. T YPES OF M ASONRY W ALLS Slide 4 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Masonry Cavity Walls Wall ties or veneer ties, made of corrosion resistant metal, span the cavity and allow the inner wythe to provide lateral support to the, usually thinner, outer wythe. Stainless steel: longest lasting Galvanized (zinc-coated) steel: less expensive Wall ties come in a great variety of configurations. In this illustration the ties also serve to hold rigid insulation boards snugly against the inner wythe. T YPES OF M ASONRY W ALLS Slide 5 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Masonry Cavity Walls Flashings: Continuous waterproof membranes that intercept water in the cavity and redirect it to the exterior Weep holes: Allow water to drain out from wall Dampproofing: Water- repellent coatings applied to the face of the inner wythe to provide additional resistance to water penetration Right: The mastic air barrier also serves as the water-repellent coating. T YPES OF M ASONRY W ALLS Slide 6 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Masonry Cavity Walls The minimum recommended cavity depth is 2 inches, to allow space for masons to keep the cavity clear of mortar droppings during construction. Water-resistant rigid insulation boards can be inserted into the cavity. But a minimum of 1 inch of clear airspace should be preserved. T YPES OF M ASONRY W ALLS Slide 7 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Masonry Cavity Walls Cavity drainage materials: Materials inserted into the cavity to catch mortar droppings and prevent obstruction of weep holes Mortar droppings should always be minimized, as they form bridges across the cavity that can allow water to bridge the cavity as well. T YPES OF M ASONRY W ALLS Slide 8 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Masonry Loadbearing Walls Carry gravity loads from other parts of the building structure (adjacent floors and roof) In modern construction, almost always reinforced Greater strength Much improved resistance to seismic forces May be composite or cavity wall construction In loadbearing cavity walls, the inner wythe is usually the loadbearing wythe and the outer wythe or veneer is nonstructural. T YPES OF M ASONRY W ALLS Slide 9 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. S PANNING S YSTEMS FOR M ASONRY B EARING W ALL C ONSTRUCTION 10 Masonry Wall Construction Slide 10 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Ordinary Construction Light wood frame interior structure, with noncombustible masonry exterior walls Right: Cavity wall Loadbearing Reinforced CMU interior wythe Brick exterior veneer S PANNING S YSTEMS FOR M ASONRY B EARING W ALL C ONSTRUCTION Slide 11 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Mill Construction Heavy timber interior structure, with noncombustible masonry exterior walls Mill construction is considered more fire- resistant than ordinary construction because the heavy timbers are slower burning than the thinner framing members of ordinary construction. S PANNING S YSTEMS FOR M ASONRY B EARING W ALL C ONSTRUCTION Slide 12 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Steel and Concrete Decks with Masonry Bearing Walls Open-web steel joists, corrugated steel decking, and concrete floor slabs with masonry bearing walls OWSJs are well suited to masonry loadbearing construction because of their relatively close spacing which imposes a more uniform load on the masonry wall. With structural steel framing at greater spacings, extra reinforcing or enlarged masonry piers may be required to carry the greater concentrated loads at bearing points. S PANNING S YSTEMS FOR M ASONRY B EARING W ALL C ONSTRUCTION Slide 13 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Steel and Concrete Decks with Masonry Bearing Walls Precast concrete hollow core slabs with cast-in-place concrete topping The wall in this example is single- wythe, fully grouted, reinforced CMU bearing wall. S PANNING S YSTEMS FOR M ASONRY B EARING W ALL C ONSTRUCTION Slide 14 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Traditional Masonry Loadbearing Wall Construction Light wood joists bearing on a traditional solid brick masonry wall Note the shallow arch construction used to span window openings. S PANNING S YSTEMS FOR M ASONRY B EARING W ALL C ONSTRUCTION Slide 15 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Traditional Masonry Loadbearing Wall Construction Traditional masonry structures are under- reinforced by contemporary standards and often must be structurally upgraded. Right: Steel straps and perimeter steel angles tie the floor to the exterior wall to improve the building's ability to transfer seismic loads from the unreinforced masonry walls, to the structural frame. S PANNING S YSTEMS FOR M ASONRY B EARING W ALL C ONSTRUCTION Slide 16 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Traditional Masonry Loadbearing Wall Construction The floors and roofs are tied to new, structural steel framing that is strategically inserted into the building and which can carry the seismic loads securely to the foundation. S PANNING S YSTEMS FOR M ASONRY B EARING W ALL C ONSTRUCTION Slide 17 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. D ETAILING M ASONRY W ALLS 10 Masonry Wall Construction Slide 18 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Flashings and Drainage Flashings are built into masonry walls to intercept water that penetrates the wall and direct the water back to the exterior. Common materials include various metals, synthetic rubber or bituminous membranes, and plastics. Materials should be chosen with longevity in mind internal flashings must last as long as the wall. D ETAILNG M ASONRY W ALLS Slide 19 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Flashings and Drainage: Metal Flashings Most expensive and most durable Stainless steel (bottom) Long-lasting Non-staining Stiffer and harder to form than copper Copper (middle) Long-lasting Runoff from flashing can cause staining by copper oxides Softer and more easily formed than stainless steel Galvanized (zinc-coated) steel (top) Less expensive Less durable Not recommended for permanent internal flashings OK for external, replaceable flashings Aluminum (not shown) Not recommended for masonry walls because this metal reacts chemically with the highly alkaline mortar D ETAILNG M ASONRY W ALLS Slide 20 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Flashings and Drainage: Membrane Flashings Self-adhering bituminous membranes (right) Polymer-modified bitumens laminated to plastic backings Self-sticking to substrate Less expensive and easier to install than metal flashings Have some capacity to self- seal around penetrations Cannot span cavities or other significant gaps without backup metal support D ETAILNG M ASONRY W ALLS Slide 21 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Flashings and Drainage: Membrane Flashings EPDM (right) Synthetic rubber Long-lasting Easy to install Other plastics May be vulnerable to tearing or other deterioration Membrane flashings cannot be permanently exposed to sunlight. They are often combined with metal where flashings must project from the wall. D ETAILNG M ASONRY W ALLS Slide 22 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Flashings and Drainage: Composite Flashings Copper or other metals laminated with heavy paper, plastic film, or other materials Material costs are less than all-metal flashings because the thinner metal sheets are used. The laminating layers provide added strength, compensating for the thinner sheet metal. Right: Copper laminated with asphalt-saturated glass fabric D ETAILNG M ASONRY W ALLS Slide 23 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Flashings and Drainage: Joining and Sealing Flashings Where flashing sections meet, the joints must be made watertight. Metals are most permanently joined and sealed by soldering or welding. Sealing with mastics is less expensive, but also less permanent. Membrane and composite flashings are sealed with mastics (right) or adhesive sealants. Self-adhering flashings are lapped and self-adhered to form a watertight seal. D ETAILNG M ASONRY W ALLS Slide 24 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Flashings and Drainage: Flashing Locations A through-wall (internal) flashing installed underneath the top-of- wall coping units intercepts water that passes between joints of those units. An external flashing, in this case a counterflashing, is installed on the back of the parapet to prevent water from passing behind and under the roof membrane termination. D ETAILNG M ASONRY W ALLS Slide 25 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Flashings and Drainage: Flashing Locations Through-wall flashings should be installed at all interruptions in the cavity. A flashing above a wall opening intercepts water in the cavity and prevents it from spilling into the opening. A flashing below a wall opening intercepts water that enters around the opening and keeps it out of the wall. D ETAILNG M ASONRY W ALLS Slide 26 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Flashings and Drainage: Flashing Locations Where a metal angle provides support to the exterior brick wythe, a flashing on top of the angle intercepts water in the cavity. The angle itself is not sufficiently watertight around its back and at its ends to act as a flashing on its own. The flashing also protects the angle from exposure to water and corrosion. D ETAILNG M ASONRY W ALLS Slide 27 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Flashings and Drainage: Flashing Locations A flashing at the base of the wall intercepts water in the cavity. D ETAILNG M ASONRY W ALLS Slide 28 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Flashings and Drainage: Flashing Locations Flashings are also used in composite walls, to intercept water that infiltrates the wall. D ETAILNG M ASONRY W ALLS Slide 29 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Flashings and Drainage: Flashing Details The backs of flashings are turned up to direct captured water toward the exterior of the wall. Flashing ends are turned up and folded to form end dams which prevent water from spilling off the ends of the flashing into the cavity. Flashings under windows and doors are often called sill pans. D ETAILNG M ASONRY W ALLS Slide 30 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Flashings and Drainage: Flashing Details Best practice: Flashings should project beyond the face of the wall at least - inch and angle downward, so that water intercepted by the flashing falls free of the wall and does not cling to the underside of the flashing and seep back into the wall. The exposed, projecting end of the flashing must be metal. Membranes and composite materials are not stiff enough and many degrade under exposure to sun light. D ETAILNG M ASONRY W ALLS Slide 31 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Flashings and Drainage: Weeps A short length of rope has been inserted into the head joint between masonry units to form a weep. In some cases, the rope will remain in the joint after the wall is completed, acting as a wick to draw water pooled on the flashing out of the cavity. In other cases, the rope is removed after the mortar has hardened, leaving a small opening. D ETAILNG M ASONRY W ALLS Slide 32 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Flashings and Drainage: Weeps Weeps formed with a small-diameter plastic tube (above) and a pre- formed plastic insert (below) Also below, the bituminous flashing membrane is creeping out from between the masonry bed joint. A better practice is to finish flashings with stiff metal edges that can protrude neatly from the wall (above). D ETAILNG M ASONRY W ALLS Slide 33 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Thermal Insulation Rigid foam, part of an Exterior Insulation and Finish System (EIFS), can be applied to the exterior side of a masonry wall. With exterior insulation, the thermal mass of the masonry is coupled to the interior conditioned environment, and can contribute to energy savings in some circumstances. D ETAILNG M ASONRY W ALLS Slide 34 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Thermal Insulation Rigid foam insulation can be inserted into the masonry wall cavity. D ETAILNG M ASONRY W ALLS Slide 35 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Thermal Insulation CMU cores can be insulated with loose granular insulation or rigid foam inserts. The effectiveness of insulation in CMU cores is limited by thermal bridging of the solid portions of the CMUs, and by the absence of insulation in cells where reinforcing and grouting is required. Bottom: Proprietary CMUs with special foam inserts can improve energy efficiency by reducing thermal bridging. D ETAILNG M ASONRY W ALLS Slide 36 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Thermal Insulation A variety of types of insulation can be applied to the inner side of the wall. Bottom: Rigid foam boards being fastened to the interior side of a CMU wall using a proprietary furring system D ETAILNG M ASONRY W ALLS Slide 37 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. S PECIAL P ROBLEMS IN M ASONRY C ONSTRUCTION 10 Masonry Wall Construction Slide 38 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Expansion and Contraction Masonry construction expands and contracts due to changes in temperature, moisture content, and structural loading. Joints must be provided to allow movement to occur without causing unsightly or detrimental cracking: Where changes in geometry create stress concentrations (right) Close to corners At intervals no greater than 125' in straight walls At changes in support conditions S PECIAL P ROBLEMS IN M ASONRY C ONSTRUCTION Slide 39 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Expansion and Contraction Joints are sealed at the surface of the wall, for appearance considerations and to prevent the uncontrolled passage of air and water. Some joint designs restrict out-of-plane movement between adjacent wall sections while permitting expansion and contraction in the plane of the wall. S PECIAL P ROBLEMS IN M ASONRY C ONSTRUCTION Slide 40 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Expansion and Contraction Vertical expansion joints in brick veneer on either side of stacked window openings A flexible sealant material that can expand and contract with movement is applied to the joint. Sealant color can be chosen to match that of the mortar and sand can be cast into the surface of the sealant before it cures, to imitate the appearance of a mortar joint. S PECIAL P ROBLEMS IN M ASONRY C ONSTRUCTION Slide 41 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Expansion and Contraction Brick expands slightly over time as it absorbs moisture from the atmosphere. Many structural systems, especially those of concrete, shrink slightly over time due to long term effects of structural loads. On multistory buildings, horizontal expansion joints must be provided in brick veneer to allow gradual expansion of the brick. If these joints are omitted, the veneer will gradually become compressed, bow outward, and eventually fail. S PECIAL P ROBLEMS IN M ASONRY C ONSTRUCTION Slide 42 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Expansion and Contraction The thin, horizontal white lines are expansion joints in the brick veneer located approximately level with the floor structure behind from which the veneer is supported. S PECIAL P ROBLEMS IN M ASONRY C ONSTRUCTION Slide 43 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Expansion and Contraction A close-up of one of the expansion joints in the last image Note the weep hole. This joint does not follow best practices: The internal flashing does not project beyond the face of the wall. The joint is not wide enough to accommodate significant movement in the veneer without risking failure of the sealant joint or overstressing of the veneer. S PECIAL P ROBLEMS IN M ASONRY C ONSTRUCTION Slide 44 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Expansion and Contraction Horizontal and vertical expansion joints are provided where changes in the supporting structure are likely to cause differential movements in the veneer. S PECIAL P ROBLEMS IN M ASONRY C ONSTRUCTION Slide 45 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Efflorescence White crystalline deposits occur on the surface of masonry when moisture within carries salts from the mortar or masonry units to the surface and then evaporates, leaving the salts behind. Efflorescence is most common with new masonry and usually decreases over time. It can be minimized by avoiding contaminants in the masonry ingredients, and by keeping water out of the wall both during and after construction. S PECIAL P ROBLEMS IN M ASONRY C ONSTRUCTION Slide 46 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Mortar Joint Deterioration Water and freeze/thaw action deteriorate mortar joints over time. Repointing: Deteriorated mortar is cut out and the joints are refinished with fresh mortar. Care must be exercised that the new mortar is not harder or more brittle than the mortar in the remainder of the joint, or early mortar failure or damage to the bricks themselves can result. S PECIAL P ROBLEMS IN M ASONRY C ONSTRUCTION Slide 47 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Moisture Resistance of Masonry Cavity wall construction limits water passage through masonry walls. Various water repellent coatings, either clear or opaque, can be applied to the wall surface. But coatings should be breathable to allow moisture that does infiltrate the wall to escape. Mortar and concrete for CMUs can be mixed with additives that increase their water repellency (right). S PECIAL P ROBLEMS IN M ASONRY C ONSTRUCTION Slide 48 Fundamentals of Building Construction, Materials & Methods, 5 th Edition Copyright 2009 J. Iano. All rights reserved. Cold and Hot Weather Construction Mortar must not freeze while it is curing: Keep materials dry. Preheat materials. Protect construction from weather and wind. Use cement types that cure rapidly and generate more heat while curing. Provide temporary space heating. In especially hot weather, mortar should be protected from water loss: Keep mortar in shade to prevent rapid water evaporation. Pre-wet masonry units to prevent excessive water absorption. S PECIAL P ROBLEMS IN M ASONRY C ONSTRUCTION