Author: Andy Fernandez

Fernandez, Andy

Summary #9: Masonry Construction/ windows & Doors

IANO / FBC / Ching

Masonry buildings are designed with layers of protection from wind, water and temperature changes of the environment. Walls are built as composite walls (stone or brick veneer with a back up wythe of CMU) and could be either load-bearing or non-loadbearing. Cavity walls prevent water penetration and include multiple components to repel water. Flashing is used in cavities to flush penetrated water out of the wall system. Thru weep holes. Flashing are usually installed in junctures of window and door openings (punch-holes) on the wall. Once installed, they are embedded into the wall. Load-bearing walls can be built with or without reinforcement (Re-Bar). CMU walls can be reinforced by post-tensioning the vertical steel Re-Bars.

Thermal insulation can be added in form of rigid foam against CMU walls to control a thermal transfer of heat. Vapor barriers are applied to the CMU surface to keep water vapor and condensation from forming in the interior of the building. Furring strips (metal or wood studs) are used to attach gypsum boards (interior finish). Furring could be sized according to insulation material, electrical and plumbing specifications. Expansion joints are added to the masonry wall to allow for thermal expansion and contraction movement due to thermal changes. Masonry walls have good acoustic insulating properties.

Although masonry walls are very strong, the weakest areas consist of the mortar joints. Mortar is porous and can transfer water from the exterior to the interior of the building if not maintained. Mortars must be kept from freezing for at least 2-3 days after curing.

Above all, masonry is usually chosen based on its unique colors, textures, patterns, fire-resistance and its compliance to the building codes.

Windows/ Doors

Windows and doors are usually pre-fabricated and made with high precision standards and weather tightness in mind. There are many types of windows: fixed, single-hung, double-hung, sliding, hopper and casement among others. The following properties relate to windows and door alike: Window and door frames are made of wood, aluminum, steel or plastic. Wood frames offer good thermal insulation but are subject to decay. Aluminum frames are strong but are high thermal conductors (a thermal plastic or rubber break is needed) and used exclusively in residential and commercial applications. Plastic frames {PVC, vinyl ( 50% of all windows sold in U.S.)} are cheaper than wood but have high thermal expansion rates. Steel frames are very strong (allows for a slender frame) are less conductive of heat than aluminum but more than wood and plastic frames.

Most prefab frames are easy to install (usually with nails or bolts) and fit in place. Solar heat gain and wintertime heat loss contribute to 30% of all heating and electrical building loads in the U.S. Thermal conductivity of the window and door frames create a very high air leakage that require large amounts of heating/cooling of the building.

Fernandez, Andy

Building Construction Illustrated –Ching / FBC Materials & Methods

Summary #8

In this reading, we learn about the importance of building exterior wall systems and their role of protection and prevention of outside elements to the interior spaces. Some of the numerous functions of the exterior walls involve keeping water out and preventing air leakage. The exterior wall serves to control heat conduction, sound transmission, water vapor, and temperature, resist fire and heat radiation among other factors. In many respects the modern exterior walls are similar to the human skin. They offer protection from water, heat and wind effects. Exterior walls must serve the effects of expansion and shrinkage of joint movements, building freeze/thaw, movement, wind / earthquake effects, corrosion and oxidation resistance and ultraviolet light effects. Some of the properties of the walls consist of air barriers, rainscreens, sealants and PEC (Pressure Equalized Chambers) and curtain walls. These smaller components offer protection from water penetration into the interior bays. Air barriers offer air from escaping or penetrating the interior while sealants block the passage of water from the outside environment. Some sealants offer resistance to expansion and shrinkage and therefore are great solutions to joint connections of structures. The rainscreen is a popular option in modern building wall cladding and serves as a shield to wind and rain. The application of the PEC in wall construction offers the control of air pressurization components to eliminate rain penetration thru small areas. Curtain walls are used as a layer of protection on the building frame. Overall, the exterior wall system is an array group of components that serves to protect the building interior just as the human skin does with thermal and water control.

Reading #7: Spans                Fernandez, Andy

In Ching’s BCI book, he discusses spanning elements and their relationship to their structural importance. A major spanning element is the arch. Arches span spaces using the compressive strengths of brick or stone while depending on the resistance of thrust by the wall. The size of the masonry units dictates the size of the arch. Another spanning tool is the lintel. Lintels span spaces of 4’-6’ respectively. They are made of one of four ways, steel angle supports, Reinforced brick filled with grout spans (8”-12”), concrete lintels with cement grout and precast lintels made of brick or concrete.

Other spanning elements include wood floor joists, decking, sub flooring, wood planks and steel open web joists. Floor joists span from 12”-24” O.C. They can span 10’-18’ distances. In comparison, steel joists range from 12’-60’ spans. Wood Joists are part of a structural subsystem and with the addition of sheathing (wood subflooring) becomes a strong structural diaphragm to transfer loads to shear components. Joists must be specified according to loads, spacing, species and defection allowance. Bridging is required with joist of 6” or deeper depth at every 8’.

Wood sub flooring is a structural component and consists of wood panels of plywood/OSB or wafer board. These panels are less susceptible to shrinkage than lumber. The panels are laid perpendicular to the joists with nails and glue (eliminates squeaks and creeps), have smooth surfaces for finished flooring and serves as an impact load resistant. Decking is usually laid over the sub flooring. Decking can be single (weakest), double or a continuous (strongest) span.

Wood plank and beams are used to distribute loads evenly by spacing elements in a grid pattern that aligns with other load bearing structure units. This system can be used as heavy timber construction if it uses fire resistive exterior walls (brick/ concrete). Disadvantages of the wood plank system include sound transmission and lack of concealment for MEP’s and insulation.

Wood beams are supported by load bearing structural elements such as masonry walls, timber, steel and concrete columns.

Steel beams and joists are also spanning units. Similar to wood framing, steel members come in nominal sizes and shapes. Steel open web joists can span distances from 12’-60’ respectively at 2’-10’ O.C. spacing. Other deeper steel joists (LH & DLH) can span from 36’-144’. Steel beams can be connected with steel angles, stiffer palters, bolts and/or welds. Similar to lumber, steel beams and joists must increase its depth to span longer distances. Some steel beams were made to alleviate this problem. One good example is the castellated beam which is deeper and longer but not heavier. Steel joists works well with rectangular one-way systems, masonry bearing walls, steel beams and suspended ceilings. These joists can support decking of wood, precast panels or concrete fill toppings. Bridging is also needed at 10’-20’ O.C. Connections to steel must resist shear and moment deflections. In summary, all spanning elements must be calculated in proportion to the distance spanned and load carrying capacity. They must be paired with vertical elements for load distribution and equilibrium.

Building Construction Illustrated: Francis Ching

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Wood: is a renewable building material that can be easily cut and dimensioned to support a wide range of structural loads. Lumber (wood cut into dimensioned sizes for specific uses) is used as boards, dimension lumber, structural lumber and timbers. Each has its own strength and load requirements. Although wood has its own natural defects (warping, moisture susceptibility and knots) it excels in tension and compression as a structural element. All wood elements such as beams, subflooring panels, joists and posts must be carefully laid out within proper spacing of other members for load bearings.

Wood beams must be spaced between 4’-8’ and be supported by timber, steel or concrete columns. Diagonal bracing and bridging must be used to avoid rotation at intervals in framing. All loads are evenly distributed with the use of a grid system that superimposes all supporting partition and load bearing elements. Wood planks are used as diaphragm reinforcement. Connections used with wood members involve steel plates, bolts, nails, metal straps, brackets and split rings (timber). Some wood elements can be left exposed for its beauty.

Masonry: Masonry brick and glazed tiles are used extensively in cladding on the building envelope. Structural clay tiles are glazed tiles used in areas of heavy wear, moisture problems, strict sanitary requirements, walls and partitions. Different wall thicknesses can be constructed, including cavity walls. Brick is also used for cavity walls, particularly using the running bond method. Standard brick walls can used Common, Flemish, Stack or Garden bonds for decorative patterns.

Steel: Steel is used in a manner like wood framing but with greater strength and no cutting. Steel beams are connected using angles, stiffer plates, bolts and welds. Each contribute to shear or moment resistance. The strength of a connection depends on the sizes of the members used.

Concrete: Concrete beams must be reinforced with steel “Re-Bars” embedded 2” from the surface of the concrete to avoid corrosion. Concrete beams must have reinforcement at the ends connected to the columns, at the bottom across the beam to deter sagging (tension moment) and at the middle top of the beam to prevent a negative bending moment. Concrete columns must also be reinforced with either rectangular or spiral steel inside running along its height to resist bucking. Splices can be used to extend the height of rebar within the columns. All reinforcement steel must start at foundation level and end at the top of column. Columns are laid out in a rectangular grid. Concrete columns can also support timber or steel beams. Precast Concrete slabs, beams and tees can also be used. Advantages of precast elements are less depth, reduced weight and longer spans. These units have a better quality finish and structural integrity.

CHAPTER 8: Among the best building materials is brick. Brick is fire resistant, comes in many colors and is modular (can fit on a human hand). Brick walls can be used along or as composite walls (brick veneer walls with CMU unit as a back up wall). Brick walls can also be reinforced with grout and steel re-bars. Bricks also are made with hollow cores to add grouting and reinforcing steel. Brick elements find uses as curtain walls, cavity walls and decorative walls. Many different patterns of courses can be used with brick walls. The most common, used for cavity walls for its shorter depth is the running bond method. The mortar joints in brick walls play a crucial function to bond the units together and keep water and wind out. Joints are usually 3/8” and Mortar comes in various colors to add to the appearance of the overall wall design. Mortar also comes in various types of strengths, from high strength to low, depending its use and location. Brink lintels can have steel angles, reinforced cement grout or precast reinforced concrete lintels. Brick lintels can span from 4’ to 6’. Brick arches can also be produced. Buildings normally have thicker walls at the bottom and thinner brick wall at the top for load support distribution.

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