A shallow foundation is a type of building foundation that transfers building loads to the earth very near to the surface, rather than to a subsurface layer or a range of depths as does a deep foundation. Shallow foundations include spread footing foundations, mat-slab foundations, slab-on-grade foundations, pad foundations, rubble trench foundations and earthbag foundations. Play media Shallow foundation construction example In ground reinforced concrete foundation in cyclonic area, Northern Australia. In ground reinforced concrete foundation in cyclonic area, Northern Australia. A spread footing foundation, which is typical in residential building, has a wider bottom portion than the load-bearing foundation walls it supports. This wider part "spreads" the weight of the structure over more area for greater stability. The design and layout of spread footings is controlled by several factors, foremost of which is the weight (load) of the structure it must support, penetration of soft near-surface layers, and penetration through near-surface layers likely to change volume due to frost heave or shrink-swell. These foundations are common in residential construction that includes a basement, and in many commercial structures. But for high rise buildings they are not sufficient. A spread footing that changes elevation in a series of vertical steps so that it follows the contours of a sloping site or accommodates changes in soil strata, is called a stepped footing. Mat-slab foundations distribute heavy column and wall loads across the entire building area, to lower the contact pressure compared to conventional spread footings. Mat-slab foundations can be constructed near the ground surface, or at the bottom of basements. In high-rise buildings, mat-slab foundations can be several meters thick, with extensive reinforcing to ensure relatively uniform load transfer. Example of slab on grade foundation Raft slab house foundation in cyclonic area, Northern Australia. Raft slab house foundation in cyclonic area, Northern Australia. Slab-on-grade or floating slab foundations are a structural engineering practice whereby the concrete slab that is to serve as the foundation for the structure is formed from a mold set into the ground. The concrete is then placed into the mold, leaving no space between the ground and the structure. This type of construction is most often seen in warmer climates, where ground freezing and thawing is less of a concern and where there is no need for heat ducting underneath the floor. The advantages of the slab technique are that it is cheap and sturdy, and is considered less vulnerable to termite infestation because there are no hollow spaces or wood channels leading from the ground to the structure (assuming wood siding, etc., is not carried all the way to the ground on the outer walls). The disadvantages are the lack of access from below for utility lines, the potential for large heat losses where ground temperatures fall significantly below the interior temperature, and a very low elevation that exposes the building to flood damage in even moderate rains. Remodeling or extending such a structure may also be more difficult. Over the long term, ground settling (or subsidence) may be a problem, as a slab foundation cannot be readily jacked up to compensate; proper soil compaction prior to pour can minimize this. The slab can be decoupled from ground temperatures by insulation, with the concrete poured directly over insulation (for example, extruded polystyrene foam panels), or heating provisions (such as hydronic heating) can be built into the slab (an expensive installation, with associated running expenses). Slab-on-grade foundations are commonly used in areas with expansive clay soil. While elevated structural slabs actually perform better on expansive clays, it is generally accepted by the engineering community that slab-on-grade foundations offer the greatest cost-to-performance ratio for tract homes. Elevated structural slabs are generally only found on custom homes or homes with basements. Copper piping, commonly used to carry natural gas and water, reacts with concrete over a long period, slowly degrading until the pipe fails. This can lead to what is commonly referred to as slab leaks. These occur when pipes begin to leak from within the slab. Signs of a slab leak range from unexplained dampened carpet spots, to drops in water pressure and wet discoloration on exterior foundation walls. Copper pipes must be lagged (that is, insulated) or run through a conduit or plumbed into the building above the slab. Electrical conduits through the slab must be water-tight, as they extend below ground level and can potentially expose wiring to groundwater. A cross section view of a rubble trench foundation The rubble trench foundation, a construction approach popularized by architect Frank Lloyd Wright, is a type of foundation that uses loose stone or rubble to minimize the use of concrete and improve drainage. It is considered more environmentally friendly than other types of foundation because cement manufacturing requires the use of enormous amounts of energy. However, some soil environments (such as particularly expansive or poor load-bearing (< 1 ton/sf) soils) are not suitable for this kind of foundation. A foundation must bear the structural loads imposed upon it and allow proper drainage of ground water to prevent expansion or weakening of soils and frost heaving. While the far more common concrete foundation requires separate measures to ensure good soil drainage, the rubble trench foundation serves both foundation functions at once. To construct a rubble trench foundation a narrow trench is dug down below the frost line. The bottom of the trench would ideally be gently sloped to an outlet. Drainage tile, graded 1:8 to daylight, is then placed at the bottom of the trench in a bed of washed stone protected by filter fabric. The trench is then filled with either screened stone (typically 1-1/2") or recycled rubble. A steel-reinforced concrete daro beam is poured at the surface to provide ground clearance for the structure. If an insulated slab is poured inside the grade beam, the outer surface of the grade beam and the rubble trench must be insulated with rigid XPS foam board, which must be protected above grade from mechanical and UV degradation. The rubble-trench foundation is a relatively simple, low-cost, and environmentally-friendly alternative to a conventional foundation, but may require an engineer's approval if building officials are not familiar with it. Frank Lloyd Wright used them successfully for more than 50 years in the first half of the 20th century, and there is a revival of this style of foundation with the increased interest in green building. The basic construction method begins by digging a trench down to undisturbed mineral subsoil. Rows of woven bags (or tubes) are filled with available material, placed into this trench, compacted with a pounder to around 1/3 thickness of pre-pounded thickness, and form a foundation. Each successive layer has one or more strands of barbed wire placed on top. This digs into the bag's weave to prevent subsequent layers from slipping, and also resists any tendency for the outward expansion of walls. The next row of bags is offset by half a bag's width to form a staggered pattern. These are either pre-filled with material and delivered, or filled in place (often the case with Superadobe). The weight of this earth-filled bag pushes down on the barbed wire strands, locking the bag in place on the row below. The same process continues layer upon layer, forming walls. A roof can be formed by gradually sloping the walls inward to construct a dome. Traditional types of roof can also be made.
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July 13, 2017 update: For the latest, please read “Zebras: Let’s Get In Formation.”A year ago we wrote “Sex & Startups.” The premise was this: The current technology and venture capital structure is broken. It rewards quantity over quality, consumption over creation, quick exits over sustainable growth, and shareholder profit over shared prosperity. It chases after “unicorn” companies bent on “disruption” rather than supporting businesses that repair, cultivate, and connect. After publishing the essay, we heard from hundreds of founders, investors, and advocates who agreed: “We cannot win at this game.”This is an urgent problem. For in this game, far more than money is at stake. When VC firms prize time on site over truth, a lucky few may profit, but civil society suffers. When shareholder return trumps collective well-being, democracy itself is threatened. The reality is that business models breed behavior, and at scale, that behavior can lead to far-reaching, sometimes destructive outcomes.Facebook — the ultimate unicorn — was weaponized to spread fake news during the presidential election. Uber has come under fire for supporting dubious political agendas, tolerating a toxic workplace culture, manipulating employee wages, and circumnavigating regulations. Medium has backpedaled, having realized that while clickbait content may produce the ad-revenue hockey stick investors want to see, it undermines the founders’ original mission to create a publishing model that enlightens, informs, and rewards quality over quantity.Many well-reasoned think pieces* have been written about the gaping chasm between the world we need and the world that exists. Today, we want to provide the seeds of a solution — and to encourage founders, investors, foundations, corporations, and their allies to organize around it.A company’s business model is the first domino in a long chain of consequences. In short: “The business model is the message.” From that business model flows company culture and beliefs, strategies for success, end-user experiences, and, ultimately, the very shape of society.We believe that developing alternative business models to the startup status quo has become a central moral challenge of our time. These alternative models will balance profit and purpose, champion democracy, and put a premium on sharing power and resources. Companies that create a more just and responsible society will hear, help, and heal the customers and communities they serve.Think of our most valuable institutions — journalism, education, healthcare, government, the “third sector” of nonprofits and social enterprises — as houses upon which democracy rests. Unicorn companies are rewarded for disrupting these, for razing them to the ground.Instead, we ought to support companies that provide extreme home makeovers. We can’t assume these companies will be created by accident. We must intentionally build the infrastructure to nurture them.ENTER THE ZEBRAThis new movement demands a new symbol, so we’re claiming an animal of our own: the zebra.Why zebras?To state the obvious: unlike unicorns, zebras are real.Zebra companies are both black and white: they are profitable and improve society. They won’t sacrifice one for the other.Zebras are also mutualistic: by banding together in groups, they protect and preserve one another. Their individual input results in stronger collective output.Zebra companies are built with peerless stamina and capital efficiency, as long as conditions allow them to survive.The capital system is failing society in part because it is failing zebra companies: profitable businesses that solve real, meaningful problems and in the process repair existing social systems.Drawing from the work of many thinkers,** we’ve developed a portrait of what a zebra company is, does, and stands for. This chart outlines how a zebra company compares with its mythical cousin, the unicorn.For a downloadable, printable version, click here.WHY IS IT SO HARD TO BUILD ZEBRA COMPANIES?In the last year we’ve spoken to countless founders, investors, foundations, and thought leaders who believe zebra companies are crucial to our society’s success. Yet zebras struggle for survival because they lack the environment to encourage their birth, let alone to support them through maturity. “I wonder how many change-makers are stuck under the demands of unicorn investors,” said TJ Abood of Access Ventures, who added that he worried about “the opportunity cost to society” under this model.From our conversations with stakeholders, we distilled the most common challenges facing zebra companies:1. The problem isn’t product, it’s process. Tech isn’t a silver bullet. Building more won’t solve the biggest challenges we face today. An app won’t address the homelessness crisis in San Francisco or unite bitterly divided partisan politicians. The obstacle is that we are not investing in the process and time it takes to help institutions adopt, deploy, and measure the success of innovation, apps or otherwise.2. Zebra companies are often started by women and other underrepresented founders. Three percent of venture funding goes to women and less than one percent to people of color. Although women start 30 percent of businesses, they receive only 5 percent of small-business loans and 3 percent of venture capital. Yet when surveyed, women — who perform better overall than founding teams composed exclusively of men — say they are in it for the long haul: to build profitable, sustainable companies.3. You can’t be it if you can’t see it. Look hard outside of Silicon Valley and you’ll find promising zebra companies. But existing and aspiring business owners haven’t seen enough proof that they’ll have a higher chance of becoming financially successful and socially celebrated if they follow sustainable business practices. They lack heroes to emulate, so they default to the “growth at all costs” model. Imagine if every fund allocated a small percentage for zebra experiments. The investing firm Indie.vc has bravely stepped into this space, but it shouldn’t stand alone.4. Zebras are stuck between two outdated paradigms, nonprofit and for-profit. For young companies pursuing both profit and purpose, the existing imperfect structures (hybrid for-profit/nonprofit, Public Benefit Corps, B-Corps, L3Cs) can be prohibitively expensive. The expense comes not only in legal fees, but in the consumption of a founder’s most precious commodity: time. Months are lost searching for aligned, strategic investors who are both familiar and comfortable with alternative models. This presents a chicken-and-egg problem for foundations, philanthropists, and investors alike. They are spooked by unproven alternative models, but companies can’t prove their models work without experiments to fund them in the first place. Moreover, the current tax system doesn’t reward — or even acknowledge — anything other than for-profit (tax) or nonprofit (deduction) strategies. From the IRS’s perspective, there is nothing akin to a “50 percent financial return, 50 percent social impact” investment. This leaves many potential investors in a straitjacket.5. Impact investing’s thesis is detrimentally narrow and risk-averse. Much of the $36 billion in impact investment funding is restricted to verticals like clean technology, microfinance, or global health. This immature market limits innovation in other sectors — like journalism and education — that could desperately use it.“So how will investors turn a profit and mitigate risks?” you may be asking. Dividends? Equity crowdfunding? We don’t have all the answers. But we’ve seen how a company’s business model and values can negatively affect the bottom line (#deleteuber). So what if the opposite is also true? What if more-enlightened dollars invested in more-enlightened companies led to stronger returns? What if companies that stood for something were in fact more profitable? Patagonia, Warby Parker, Zingerman’s, Etsy, Mailchimp, Basecamp, and Kickstarter are a start — but the world needs so much more.MAKE ZEBRAS: JOIN USIf you believe technology and capital must do better, if you are building a zebra company or want to help carve out a space for them to thrive: join usOur goal is to gather zebra founders, philanthropists, investors, thinkers, and advocates to meet in person this year for DazzleCon (November 15–17 in Portland, Oregon)— a group of zebras is called a dazzle! — to learn from one another and pool resources, ideas, and best practices, to collectively advance this set of ambitions. From this gathering, we will capture and share the unique patterns that zebra founders and funders are finding, and we’ll turn a loose network into a powerful, cohesive movement.Are you in? Go here.Jennifer Brandel is the co-founder and CEO of Hearken. Mara Zepeda is the co-founder and CEO of Switchboard. Extra special thanks to Astrid Scholz, founder and CEO of Sphaera.DazzleCon is proudly supported by Knight Foundation, Artha Investing for Impact, Social Capital Markets, Portland Incubator Experiment, and Catalyst Law. Interested in sponsoring? Get in touch.*Thought piece roundup: Anil Dash on Humane Tech, Joe Edelman’s “Nothing to be Done,” Victoria Fram’s “Why An Equity-Only Investment Strategy Overlooks Many Promising Entrepreneurs,” Caterina Fake’s “The Age of the Cockaroach,” Jason Fried’s “Why We Chose Profit,” Christie George’s “Investing in Sharing,” Tristan Harris’s “How Technology Hijacks People’s Minds — from a Magician and Google’s Design Ethicist,” David Heinemeier Hansson’s “Exponential Growth Devours and Corrupts,” Julie Menter’s “On Unicorns: We’re Looking for a Different Kind of Magic,” Tim O’Reilly’s “We’ve Got This Whole Unicorn Thing Wrong,” Andrew Wilkinson’s “Unicorns vs. Horses.”**Jenn Armbrust’s Feminist Business School, Amber Case’s Calm Technology, Jerry Colonna, Ali Schultz and the work of Reboot.io, Anil Dash in conversation with Krista Tippett, in On Being; Seth Godin’s Tribes: We Need You to Lead Us; Jonathan Harris’ Modern Medicine; Ivan Illich’s Deschooling Society; Michael Karlberg’s “Beyond the Culture of Contest”; Jerry Michalski’s “What if we Trusted You?,” Howard Rheingold’s “Toward a Literacy of Cooperation”; Douglas Rushkoff’s Throwing Rocks at the Google Bus; Natasha Dow Schüll’s Addiction by Design; Shel Silverstein’s poem “Zebra Question”; Peter Thiel’s Zero to One; Ari Weinzweig’s Anarchist’s Guide to Building a Better Business series. Zebra companies have been referred to in journalism articles and academic papers, and by some VC firms.Thanks to Jenn Armbrust, Adam Brault, David Chen, Molly deAguiar, John Dimatos, Lennon Day-Reynolds, Corey Ford, Christie George, Seth Godin, Andrew Haeg, Jason Kunesh, Rachel Hankerson, Jonathan Harris, Jennifer Jordan, Luke Kanies, Duncan Malashock, Kanyi Maqubela, Ellen Mayer, Julie Menter, Douglas Rushkoff, Jake Shapiro, Michael Slaby, Rick Turoczy, Stephanie Pereira, April Rinne, Tom Watson. And to Jen McDonald for editing; and to Arthur Jones for the illustrations.
For other uses of "repair", see Maintenance, repair, and operations. Home repair involves the diagnosis and resolution of problems in a home, and is related to home maintenance to avoid such problems. Many types of repairs are "do it yourself" (DIY) projects, while others may be so complicated, time-consuming or risky as to suggest the assistance of a qualified handyman, property manager, contractor/builder, or other professionals. Repair is not necessarily the same as home improvement, although many improvements can result from repairs or maintenance. Often the costs of larger repairs will justify the alternative of investment in full-scale improvements. It may make just as much sense to upgrade a home system (with an improved one) as to repair it or incur ever-more-frequent and expensive maintenance for an inefficient, obsolete or dying system. For a DIY project, it is also useful to establish limits on how much time and money you're willing to invest before deciding a repair (or list of repairs) is overwhelming and discouraging, and less likely to ever be completed. Repairs often mean simple replacement of worn or used components intended to be periodically renewed by a home-owner, such as burnt out light bulbs, worn out batteries, or overfilled vacuum cleaner bags. Another class of home repairs relates to restoring something to a useful condition, such as sharpening tools or utensils, replacing leaky faucet washers, cleaning out plumbing traps, rain gutters. Because of the required precision, specialized tools, or hazards, some of these are best left to experts such as a plumber. One emergency repair that may be necessary in this area is overflowing toilets. Most of them have a shut-off valve on a pipe beneath or behind them so that the water supply can be turned off while repairs are made, either by removing a clog or repairing a broken mechanism. Perhaps the most perplexing repairs facing a home-owner are broken or damaged things. In today's era of built-in obsolescence for many products, it is often more convenient to replace something rather than attempt to repair it. A repairman is faced with the tasks of accurately identifying the problem, then finding the materials, supplies, tools and skills necessary to sufficiently effect the repair. Some things, such as broken windows, appliances or furniture can be carried to a repair shop, but there are many repairs that can be performed easily enough, such as patching holes in plaster and drywall, cleaning stains, repairing cracked windows and their screens, or replacing a broken electrical switch or outlet. Other repairs may have some urgency, such as a broken water pipes, broken doors, latches or windows, or a leaky roof or water tank, and this factor can certainly justify calling for professional help. A home handyman may become adept at dealing with such immediate repairs, to avoid further damage or loss, until a professional can be summoned. Periodic maintenance also falls under the general class of home repairs. These are inspections, adjustments, cleaning, or replacements that should be done regularly to ensure proper functioning of all the systems in a house, and to avoid costly emergencies. Examples include annual testing and adjustment of alarm systems, central heating or cooling systems (electrodes, thermocouples, and fuel filters), replacement of water treatment components or air-handling filters, purging of heating radiators and water tanks, defrosting a freezer, vacuum refrigerator coils, refilling dry floor-drain traps with water, cleaning out rain gutters, down spouts and drains, touching up worn house paint and weather seals, and cleaning accumulated creosote out of chimney flues, which may be best left to a chimney sweep. Examples of less frequent home maintenance that should be regularly forecast and budgeted include repainting or staining outdoor wood or metal, repainting masonry, waterproofing masonry, cleaning out septic systems, replacing sacrificial electrodes in water heaters, replacing old washing machine hoses (preferably with stainless steel hoses less likely to burst and cause a flood), and other home improvements such as replacement of obsolete or ageing systems with limited useful lifetimes (water heaters, wood stoves, pumps, and asphaltic or wooden roof shingles and siding. Often on the bottom of people's to-do list is home maintenance chores, such as landscaping, window and gutter cleaning, power washing the siding and hard-scape, etc. However, these maintenance chores pay for themselves over time. Often, injury could occur when operating heavy machinery or when climbing on ladders or roofs around your home, so if an individual is not in the proper physical condition to accomplish these chores, then they should consult a professional. Lack of maintenance will cost more due to higher costs associated with repairs or replacements to be made later. It requires discipline and learning aptitude to repair and maintain the home in good condition, but it is a satisfying experience to perform even seemingly minor repairs. Another related issue for avoiding costly repairs (or disasters) is the proper operation of a home, including systems and appliances, in a way that prevents damage or prolongs their usefulness. For example, at higher latitudes, even a clean rain gutter can suddenly build up an ice dam in winter, forcing melt water into unprotected roofing, resulting in leaks or even flooding inside walls or rooms. This can be prevented by installing moisture barrier beneath the roofing tiles. A wary home-owner should be alert to the conditions that can result in larger problems and take remedial action before damage or injury occurs. It may be easier to tack down a bit of worn carpet than repair a large patch damaged by prolonged misuse. Another example is to seek out the source of unusual noises or smells when mechanical, electrical or plumbing systems are operating—sometimes they indicate incipient problems. One should avoid overloading or otherwise misusing systems, and a recurring overload may indicate time for an upgrade. Water infiltration is one of the most insidious sources of home damage. Small leaks can lead to water stains, and rotting wood. Soft, rotten wood is an inviting target for termites and other wood-damaging insects. Left unattended, a small leak can lead to significant structural damage, necessitating the replacement of beams and framing. With a useful selection of tools, typical materials and supplies on hand, and some home repair information or experience, a home-owner or handyman should be able to carry out a large number of DIY home repairs and identify those that will need the specialized attention of others. When a home is sold, inspections are performed that may reveal environmental hazards such as radon gas in the basement or water supply or friable asbestos materials (both of which can cause lung cancer), peeling or disturbed lead paint (a risk to children and pregnant women), in-ground heating oil tanks that may contaminate ground water, or mold that can cause problems for those with asthma or allergies. Typically the buyer or mortgage lender will require these conditions to be repaired before allowing the purchase to close. An entire industry of environmental remediation contractors has developed to help home owners resolve these types of problems.