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Pier and Beam vs Slab Foundations | Which one should you choose? - YouTube
Channel: Belinda Carr
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foundations are a critical part of a
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building structure they serve numerous
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purposes they bear the load of the
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building its inhabitants contents snow
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and rain they distribute these loads
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over a large area to prevent excessive
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settlement they provide protection
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against natural forces like earthquakes
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tornadoes and floods because they are
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embedded into the soil they provide
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lateral stability and prevent buildings
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from sliding away they resist decay from
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bugs and soil they protect buildings
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from freeze thought cycles and the
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expansion and contraction of soil they
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also provide a level surface to start
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constructing a building
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two popular types of foundations are
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pure and beam and slab foundations in
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this video we're going to look at how
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they're made the upfront costs long term
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costs protection from the elements where
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they should be used and whether one is
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better than the other let's start with
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pure and beam or post in beam
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foundations the older construction
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method that is found on homes built
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before 1960.
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first a series of holes are dug into the
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ground five to ten feet apart
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these holes must hit bedrock which can
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be four feet below the surface or 50
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feet large cardboard tubes are sunk into
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the soil plastic bases can be added to
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the bottom to increase the size and
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carrying capacity of the piers this
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helps to ensure that the piers won't
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shift circular rebar cages are placed in
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the middle of the voids
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these tubes must be perfectly straight
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and level
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next the voids are filled with concrete
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and a base connection is embedded in the
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top of the pier
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beams are extended from one pier to
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another these will support the joists
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and the flooring of the home
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usually the crawl space underneath the
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beams is about 18 inches from the ground
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this is where the home's plumbing and
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electrical components are located there
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are several variations of pure and beam
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foundations the piers can be made of
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precast concrete brick stone or
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cedarwood which is resistant to rot and
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decay the crawl space or the area under
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the building can be vented or unvented
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slab on grade or monolithic slab
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foundations are a newer construction
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method the concrete slab sits directly
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on the ground
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first the surface is leveled and a
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perimeter form is created for the
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foundation
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four to six inches of gravel is spread
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inside
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a layer of plastic sheathing is laid
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down to act as a moisture barrier
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engineered steel rebar reinforces the
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concrete foundation
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concrete is poured over the gravel and
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plastic sheathing and allow to cure
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a newer version of slab on grade
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foundation is a post tension slab steel
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cables are laid out in a grid inside the
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formwork
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after the slab has been cast the cables
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are tightened which gives the foundation
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tensile strength
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a type of monolithic slab is a floating
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slab foundation in this method the
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horizontal slab is not connected to the
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vertical foundation it simply sits on
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the ground and can move above the frost
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line as a monolithic unit it is used for
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garages workshops sheds and adus or
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additional dwelling units
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pure and beam and slab on grade
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foundations are mainly found in the
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southern parts of the u.s
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northern states have conditioned crawl
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spaces and foundations with basements
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the reason slab on grade foundations are
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so popular nowadays is because it's
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easier to construct and has a lower
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upfront cost compared to pure and beam
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foundations
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soils in texas can vary drastically they
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can have a couple of inches of topsoil
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three to four feet of clay before
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hitting rock or they can have more than
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50 feet of clay before hitting rock the
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cost of pure and beam foundations is
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unpredictable because of the different
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depths of clay soil the cost of slab on
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grade foundations is more predictable
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because it doesn't need to hit bedrock
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but the lower upfront costs of slab
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foundations means higher long term costs
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like foundation repair peer and beam
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foundations have individual peers and
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beam members so it's easier to isolate
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foundation problems and it's cheaper to
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repair slab on grade foundations can
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shrink crack and even sink they are more
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difficult and expensive to repair
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we had to install 22 concrete piers to
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level the foundation of our previous
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home
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fortunately they only needed to be
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installed on the perimeter and not
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inside our home
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concrete slabs are in constant contact
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with the soil
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texas has clay soils that expand and
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contract throughout the year because of
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moisture fluctuations
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if soils swell the foundation will be
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pushed upwards if the soil shrinks and
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separates from the foundation it will be
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unsupported and will crack
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foundation repair is a huge business
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here because every home has either had
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foundation repairs or will need it in
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the future homeowners are encouraged to
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water the soils around their foundation
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to balance the moisture levels
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throughout the year
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repairing electrical and plumbing issues
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is also easier and cheaper when you have
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a parent beam foundation thanks to the
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crawl space underneath with a slab
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foundation repairing any electrical or
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plumbing issues is a messy and
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destructive and expensive process you
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have to jackhammer the slab and cut the
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steel rebar to access any pipes the
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lifespan of the concrete slab is lowered
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to get to the utilities underneath we
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discussed this in my video on planned
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obsolescence i'll link it up here also
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any foundation work on post tension
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slabs is very dangerous people have been
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dismembered and killed because they hit
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a cable which then burst through the
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concrete i've heard plumbers compare
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cutting through post tension slabs to
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diffusing a bomb
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another feature to consider is the
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ability to add levels of stories to your
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home
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you could technically add additional
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peers and beams to support another level
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you could also detach your purin beam
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home from the foundation and move it to
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a completely different site
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last year a 140 year old historic
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victorian house was moved on dollies
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through the streets of san francisco
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moving in just six blocks from franklin
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street to fulton street cost a whopping
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four hundred thousand dollars this is
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possible with pure and beam foundations
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because they are detachable houses built
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on slab foundations are anchored down
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and cannot be moved
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before we move on to other differences
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between pure and beam and slab
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foundations i'd like to introduce the
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sponsor of this portion of the video
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goals and interests i recently took
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mkbhd's class on youtube success even
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though the subject matter of his videos
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is different than mine he had a lot of
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invaluable lessons
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if you'd like to check this out the
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first thousand people to use the link in
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the description will get a one month
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free trial of skillshare
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now let's compare how pure and beam and
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slab foundations protect us from the
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elements unvented pure and beam
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foundations can be insulated with
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fiberglass or spray foam this can help
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lower your energy bills and make your
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home feel more comfortable
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vented pure and beam foundations are a
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different issue
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the flows of such homes can be cold in
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winter months because of the air
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exchange that occurs in the crawl space
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these spaces can also become damp and
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even accumulate water during heavy rains
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slab on grade foundations don't have
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this problem however if you don't use a
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vapor barrier underneath moisture from
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the ground can seep through the concrete
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pests and rodents often seek shelter in
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crawl spaces and can build nests beneath
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your home they can also cause damage to
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your wiring and structural members
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larger pests can be kept out of the
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crawl space by placing a lattice over
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the access
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slab on grade foundations don't have
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this issue but termites could enter
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through any cracks or openings
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in terms of comfort flows on parent beam
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foundations sound hollow and squeaky but
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they are easier on your feet because
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they can flex
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concrete slab foundations are solid and
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quiet but standing on them all day long
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can be tough on your feet finally where
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to use them pure and beam foundations
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are better in areas with substantial
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soil expansion and contraction like
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texas they are also ideal for homes
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built on uneven grade homes built into a
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hillside or for homes built off the
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ground due to potential flooding
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slab foundations are ideal for level
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sites in regions that get a lot of
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moisture and areas where freezing
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weather is common in winter underground
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pipes are insulated by the foundation
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and earth and are less likely to burst
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slabs are also easier to build and
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require less expertise
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both pier and beam and slab on grade
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foundations have their advantages and
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disadvantages i wouldn't make a blanket
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statement saying that one is better than
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the other because there are so many
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factors to consider your site budget
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soil conditions weather etc we should
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probably use pure and beam foundations
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here in texas but it can be too
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expensive in certain areas slab on grain
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foundations that are built on stable
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soil could last decades without any
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issues i'd like to end this video with a
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story that a foundation repair guy told
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me last year he said that with old slab
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foundations if the end breaks off it can
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be picked up with concrete peers like
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the work that was done on my previous
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home
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however with new post-tension slabs the
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ends don't break off the whole slab and
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the house tilts
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so he said that when newer homes get
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foundation repairs in a decade or so
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they will have to pay four times more
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and need invasive interior peers that's
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something to look forward to
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i hope i was able to simplify these
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topics let me know if i should make
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additional videos on helical piers
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friction piers for skyscrapers and even
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basement foundations in northern regions
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i'll link my patreon page in the
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description if you can support me i'd
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really appreciate it a big thank you to
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everyone already supporting me don't
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forget to hit the like button subscribe
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button and the notification bell too
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thanks for watching see ya
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