****** - Verified Buyer
4.5
The book title and description are both misleading. This book deals only with wood-frame residential construction. Yet the dust-jacket description does not mention this very important limitation of the book. My specialty is concrete construction, so I checked out the index for mentions of concrete. There are a few but they are flawed and full of misinformation. Here are a few examples:On page 209, a sentence states that: "Contractor shall verify that flatwork...does not pond water."The problem: All flatwork ponds water because it can't be constructed perfectly flat. A very tight tolerance of an eighth-inch gap under a 10-ft straightedge means there is going to be a puddle or dip an eighth-inch deep if the slab is level. When exterior flatwork is built with a slope, there will still be some water ponded at the downhill bottom of any dip. .On page 99, a sentence states: "In slab on grade foundations, the concrete must be reinforced so that it does not crack..."The problem: Reinforcing steel--whether bars or welded wire mesh--does not prevent cracking. It helps to hold the crack faces together so the cracks don't get too wide. If you put enough reinforcing steel in the slab it will develop a large number of very fine cracks because the steel restrains shrinkage and puts the concrete in tension. Concrete is very weak in tension. Sawed or tooled joints are used to hide cracks in either a straight line cut or tooled groove.Also on page 99: "Either material [welded wire mesh or rebars] can be used, but both must be placed in the middle of the concrete slab."The problem: To control cracking of a nonstructural slab on ground, the reinforcement needs to be near the top of the slab. Usually 1 to 2 inches below the surface. The closer to the surface, the better the reinforcement works in holding crack faces tightly closed. The reduced cover may reduce resistance to rusting of the steel, but that problem is not as great as wide cracks. In floors 4-in. thick, steel in the middle (2 inches below the surface) is acceptable. In floors thicker than 4 inches, the steel must still be 1 to 2 in. below the surface.Again, on page 99: "To accomplish this, the reinforcing steel must be held up off the ground, using small supports made of metal or plastic."The problem: Most residential work is done with light gage welded wire mesh. To keep the mesh near the design elevation requires so many bolsters or chairs that there is almost as much steel in the supports as there is in the reinforcement. The problem is that workers have to walk in the concrete while placing it and striking it off. When they do this they step on the mesh and drive it to near the bottom of the slab. It doesn't bounce back up, and can't be hooked up if the person doing the hooking is standing on the mesh.And finally, on page 99: "When the reinforcement is placed in the bottom of the slab and not in the middle, this weakens the slab and makes it susceptible to cracking."The problem: Reinforcement at the bottom of the slab doesn't weaken it.The reinforcement just doesn't fulfill it's purpose of holding surface crack faces tightly together so the cracks don't open too wide.On page 102: "A vapor barrier is customarily a layer of thin plastic...sandwiched between two layers of sand, each of which is 2 inches thick"The problems: The description is for a vapor retarder unless the plastic sheeting is thicker than about 15 mils. The term retarder means the sheeting does transmit some vapor. But the larger problem is the suggestion that sand be placed both above and below the vapor retarder. For floors that will receive most coverings, or floors in areas requiring humidity control, the concrete slab must be placed directly on top of the vapor retarder. If there's a layer of sand on top of the vapor retarder, any water in the sand is trapped between the concrete slab and the vapor retarder. It can exit only through the slab surface. And that can damage flooring of nearly all kinds. Further, many sands can't be compacted well and produce a very poor base for the concrete. Only compaced crusher-run sand or similar materials that contain some dust-like fines form a srong base for the slab.I stopped reading the book after noting that it does not cover anything but wood frame construction and contains many errors on subjects I'm familiar with. Save your money by not buying this book.Ward Malisch, P.E., PhD
