Shallow foundation

<h2 id="types">Types</h2>
<p>Footings are always wider than the members that they support. Structural loads from a <a href="/facts/Column/NDtghP75">column</a> or wall are usually greater than 1,000 kPa, while the soil's <a href="/facts/Bearing_capacity/dNPtXzze">bearing capacity</a> is commonly less than that (typically less than 400 kPa). By possessing a larger bearing area, the foundation distributes the pressure to the soil, decreasing the bearing pressure to within allowable values.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> A structure is not limited to one footing. Multiple types of footings may be used in a construction project.
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<h3>Wall footing</h3><p>
Also called <i>strip footing</i>, a <a href="/facts/Wall_footing/GgjFImEC">wall footing</a> is a continuous strip that supports structural and non-structural load-bearing walls. Found directly under the wall, Its width is commonly 2-3 times wider than the wall above it.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a></p>
<h3>Isolated footing</h3>
<p>Also called <i>single-column footing</i>, an isolated footing is a square, rectangular, or circular slab that supports the structural members individually. Generally, each column is set on an individual footing to transmit and distribute the load of the structure to the soil underneath. Sometimes, an isolated footing can be sloped or stepped at the base to spread greater loads. This type of footing is used when the structural load is relatively low, columns are widely spaced, and the soil's bearing capacity is adequate at a shallow depth.
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<h3>Combined footing</h3>
<p>When more than one column shares the same footing, it is called a <i>combined footing</i>. A combined footing is typically utilized when the spacing of the columns is too restricted such that if isolated footing were used, they would overlap one another. Also, when property lines make isolated footings eccentrically loaded, combined footings are preferred.
</p><p>When the load among the columns is equal, the combined footing may be rectangular. Conversely, when the load among the columns is unequal, the combined footing should be <a href="/facts/Trapezoidal/nCBKsauz">trapezoidal</a>.
</p>
<h3>Strap footing</h3><p>
A <a href="/facts/Strap_footing/VdMe9QCN">strap footing</a> connects individual columns with the use of a strap beam. The general purpose of a strap footing is alike to those of a combined footing, where the spacing is possibly limited and/or the columns are adjacent to the property lines.</p>
<h3>Mat foundation</h3><p>
Also called <i>raft</i> foundation, a mat foundation is a single continuous slab that covers the entirety of the base of a building. Mat foundations support all the loads of the structure and transmit them to the ground evenly. Soil conditions may prevent other footings from being used. Since this type of foundation distributes the load coming from the building uniformly over a considerably large area, it is favored when individual footings are unfeasible due to the low bearing capacity of the soil.</p>
<h2 id="slab-on-grade-foundation">Slab-on-grade foundation</h2>
<p class="note">"Floating foundation" redirects here. For Floating raft system, see <a href="/facts/Floating_raft_system/6vH2Gx7K">Floating raft system</a>.</p>

<p><i>Slab-on-grade</i> or <i>floating slab</i> foundations are a <a href="/facts/Structural_engineering/Wj1vpoGh">structural engineering</a> practice whereby the <a href="/facts/Reinforced_concrete/aUTUKAQF">reinforced concrete</a> slab that is to serve as the foundation for the structure is formed from <a href="/facts/Formwork/SKTrrBYn">formwork</a> set into the ground. The concrete is then poured into the formwork, 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. Frost Protected Shallow Foundations (or FPSF) which are used in areas of potential frost heave, are a form of slab-on-grade foundation.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a>
</p><p>Remodeling or extending such a structure may be more difficult. Over the long term, ground settling (or <a href="/facts/Subsidence/EIwtz9w9">subsidence</a>) 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, <a href="/facts/Extruded_polystyrene/dfIVntty">extruded polystyrene</a> foam panels), or heating provisions (such as <a href="/facts/Hydronic_heating/401aamPN">hydronic heating</a>) can be built into the slab.
</p><p>Slab-on-grade foundations should not be used in areas with <a href="/facts/Expansive_clay/JsaySWsq">expansive clay</a> 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 <a href="/facts/Tract_home/JNEW9FLX">tract homes</a>. Elevated structural slabs are generally only found on custom homes or homes with basements.
</p><p><a href="/facts/Copper/I8PEE8oX">Copper</a> piping, commonly used to carry <a href="/facts/Natural_gas/9MYQ7NAP">natural gas</a> and <a href="/facts/Water/0lkXnJPK">water</a>, 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.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> Copper pipes must be <i>lagged</i> (that is, <i><a href="/facts/Building_insulation/qSMbCIfY">insulated</a></i>) or run through a <a href="/facts/Water_pipe/rt4WXDXw">conduit</a> or <a href="/facts/Plumbing/rt4WXDXw">plumbed</a> 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 <a href="/facts/Groundwater/JYM2IDS2">groundwater</a>.
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<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Argillipedoturbation/d4jywdXT">Argillipedoturbation</a></li>
<li><a href="/facts/Building_construction/58eqDhy9">Building construction</a></li>
<li><a href="/facts/Construction_engineering/rY2vMT8B">Construction engineering</a></li>
<li><a href="/facts/Fiber_reinforced_concrete/MXaDrfcw">Fiber reinforced concrete</a></li>
<li><a href="/facts/Grade_beam/1StB6GHe">Grade beam</a></li>
<li><a href="/facts/Precast_concrete/fEk8G0Fw">Precast concrete</a></li>
<li><a href="/facts/Prestressed_concrete/0fFlgCju">Prestressed concrete</a></li>
<li><a href="/facts/Rebar/qm27fUbk">Rebar</a></li>
<li><a href="/facts/Steel_fixer/G5cSA7o7">Steel fixer</a></li>
<li><a href="/facts/Tie_rod/NXCdXAnC">Tie rod</a></li></ul>

<h2 id="external-links">External links</h2>

Wikimedia Commons has media related to Shallow foundations.

<ul><li><a href="http://www.theconstructioncivil.org/raft-or-mat-foundations/">Raft or Mat Foundations</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Akhter, Shahin. "Shallow foundation – Definition, Types, Uses and Diagrams". Pro Civil Engineer. Retrieved July 31, 2021. <a href="https://procivilengineer.com/shallow-foundation/" target="_blank">https://procivilengineer.com/shallow-foundation/</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Gillesania, Diego Inocencio T. (2004). Fundamentals of reinforced concrete design (2nd ed.). [Cebu, Cirty, Philippines]. p. 259. ISBN 971-8614-26-5. OCLC 1015901733.{{cite book}}:  CS1 maint: location missing publisher (link) <a href="971-8614-26-5" target="_blank">971-8614-26-5</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Mahdi, Sheikh. "8 Most Important Types of Foundation". civiltoday.com. Retrieved July 31, 2021. <a href="https://civiltoday.com/geotechnical-engineering/foundation-engineering/161-types-of-foundation" target="_blank">https://civiltoday.com/geotechnical-engineering/foundation-engineering/161-types-of-foundation</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>"Slab-on-Grade Foundation Detail & Insulation, Building Guide". <a href="https://www.ecohome.net/guides/2280/slab-on-grade-construction-step-by-step-guide" target="_blank">https://www.ecohome.net/guides/2280/slab-on-grade-construction-step-by-step-guide</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>"Slab Leak Repair McKinney, Frisco, and Allen Tx - Hackler Plumbing". Hacklerplumbingmckinney.com. 2013-11-08. Retrieved 2018-08-20. <a href="http://hacklerplumbingmckinney.com/slab-leak-repair/" target="_blank">http://hacklerplumbingmckinney.com/slab-leak-repair/</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
</ol>

Shallow foundation open-in-new

Shallow foundation