Foundations - Slab vs. Pier and Beam - Which is better?

hey guys company from a new construction job site here in Austin Texas my company's just about to start framing on this brand new house being built and this is a slab on grade foundation that means that the concrete right here is poured right on top of the ground and the house will get framed on top of that there's no basement there's no crawlspace under here now this is probably the most common foundation on new homes being built in Texas in about the last 20 or so years however there's another type of foundation you also might want to consider for your new house that's a pier and beam foundation on the build show today we're gonna take a deep dive on the differences between slab on grade and pier and beam foundations we're gonna talk about the pros and cons and which one might be right for your new build it's almost a hundred outside today there so instead of filming this at the job I'm gonna meet you back at the office and we'll film it there let's get going all right guys it was hot on the jobsite so thanks for letting me come back to the office here we're gonna take a deep dive today on two different types of foundations that are pretty common in the south but you'll also see these in the Pacific Northwest in some of the south eastern states as well you're not going to see slabs or peering beams typically though in the real cold climates this is gonna be a little more of a temperate climate foundation so first off let's take a look at slab foundations now this is a job in South Austin that I completed not too long ago and we actually did a full in-ground foundation so if you're in the north this is probably more like what you're used to seeing these are you know somewhere between eight and ten foot maybe even deeper basement walls where you've got concrete walls all the way down but one of the main reasons why we don't do slabs in Texas in particular is this right here this is that that same foundation backed up to when we were doing excavation if you look at this soil conditions here we've got maybe just a couple of three or four inches of actual topsoil and then in this case we had about three to four feet of clay and then from this line on down that's nothing but solid rock so for us to put a foundation in it was a bear we had a ton of this right here which is excavation with a hoe Ram this basically is a hammer on the end of a pneumatic tool that's going to hammer down tipped it and pop that rock out and you can see it came out in little pieces that took us a ton of time to actually put that foundation on the ground so let's talk about slabs first as I mentioned on the intro it's probably the most common foundation for southern US homes as a slab on grade relatively straightforward to understand but let me walk you through it anyways just to make sure we're both in the same page here's a slab on grade foundation you can see we're basically at grade here at the garage section but then as you go downhill here at the very end we were probably three to four feet maybe out of the ground on this section of the slab and the living section is on this right-hand side here this slab has been polished relatively smooth and one of the things about slab foundations is that you can actually use that structural slab as your finished floor you see a lot of tile on the southern US homes even Texas homes because we've got that concrete you can tile right onto but you could actually just polish this grind it put a sealer on it whatever you want and you've got a finished floor there now one of the things I like about slabs right away is this it's a incredibly durable foundation if it's done right there's really hardly anything that can go wrong with a slab that being said I will talk about some issues here in a little bit but slabs are very solid generally speaking a very excellent foundation because of lack of movement and changes compared to other types okay so here's let's back up a little bit in the process in the slab these are the guys that are actually placing a slab I did a couple years ago you see we've got a truck and we've got a concrete pump pumping it down it's usually all poured monolithically meaning all poured at one time now production builders use a specific type of slab called a post tension slab now we're gonna get into this specifics and there's two main types of slab on grade foundations post tension and a rebar slab so for instance on this house that I was visiting one of the tell-tale signs hopefully you can see it on this picture here is you're gonna see these little marks right here on the foundation and they're like a little pock mark that's gotten parge Dover or stuccoed over and that's a real big telltale sign that you've actually got a post tension slab now here's what that look like prior to pour you can see you've got a cable on here that's a post tensioning cable these are cables that can take a massive amount of pressure and what happens is they lay the cables loose on the slab the slab is poured and then later they bring a device on there it's actually going to pull the cable it actually is pushing against the concrete and pulling those cables they're tensioned post after the after the fact that's why they call it a post tension slab and what happens is the slab once those cables are tensioned the whole slab is kind of holding together because of these cables now that's a good way to if you want to minimize cracking and that's why production builders like it but one of the big downsides of a post-tensioned slab is if you do any work later and you happen to cut one of those tensioning cables it's a really really big deal to fix it and if you had a problem with one of those cables during construction again really really big deal okay so instead of that let me show you my preference when it comes to slab on grade and this is actually all I've ever built with in the last 15 years now we're kind of working our way back on this here's that same slab earlier and now you're gonna see what I like which is a rebar slab and here's what that's going to look like pre pour what's happening is you've got a grid through the slab of beams these are varying depth depending on what the soil engineer tells us to do but then they're gonna put a grid work of rebar inside the beams and those beams are crossing each other and then there's also a rebar grid that happens on the top part of the slab the slab itself in the field here on top of this vapor barrier this area is typically four to five inches deep and then these beams you may see those as shallow as maybe 18 inches to as much as maybe 36 or even deeper and then usually there's a perimeter beam now there also may be some additional supports underneath that slab and in this case it's you can't really tell but this is actually a steel pile supported slab so we're building right here on the lake we had some serious amount of piles now here's one of the things that I don't like about slab foundations they are incredibly hard to upgrade and repair this is my friend's house there was complaining of some sewer smell and their bathroom six months or so after the contractor finished his bathroom remodel and with a little investigation work I realized oh my gosh he doesn't have a p-trap on this shower and so the sewer gases were coming right up through the shower and the only thing you can do of course is jackhammer that out and it's a lot of work to do a remodel to do an upgrade to do a repair on any plumbing that's in it that's in a slab check out what else I saw inside this slab when I pulled it out this is not the point of the video but that totally shocked me I couldn't believe what I was seeing in there some flex pipe obviously not meant to be buried and was totally buried turns out this this remodel project got no permits and they made a lot of errors we ended up uncovering a bunch of things that we had to fix for my friend but slab on grades often will have this type of repair done to them this is a after the fact leveling where a company came out they they basically punched a bunch of holes in the slab in various places they'll put a jack underneath the beam and they'll jack it up so that they can repair that foundation very hard to do very invasive man it's just it's brutal on the house and the homeowner so that's one big downside of slab foundations let's fast forward a little bit through these photos in the interest of time here's just a few more under constructions from various slabs I've done over the years and let's take a look at oh actually this photo I do want to mention you see if I can go back sorry oh this is a great shot this is a drone shot from one of those earlier slabs that I was talking about on the lake so this is taken from you know 150 feet or so above the house the yellow that you're seeing there is a vapor barrier that's a product by stego that I like to use it's gonna keep ground water and soil moisture from getting that slab wet and that's all the way even underneath my slab it's also taped where I have seams and then you can start to get a feel for that rebar grid that's throughout there and then as I mentioned on this house everywhere there's an intersection there's a steel pile that the pile guys drove all the way down to rock so in effect this slab on grade is kind of like a house at the ocean that's up on piers and in between the bottom of the slab and the rock which in this case was 50 feet down we've got some really bad soil with some potential for movement or change so we've basically pinned the house with those piles all the way down to Rock the last thing I want to mention about slab foundations that I really like is that there's no water issues I mentioned that we have a stego vapor barrier underneath this house you have no basement you have no crawlspace there's really no basement waterproofing than needs to happen on a slab on grade another reason why production builders like him and frankly said why there's no pest there's no critters there's no raccoons under your house when that house is on a slab on grade you've got a firm foot on the house that's sitting right on the ground and there's no issues with water pass all that other kind of stuff okay now let's switch and take a look at pier and beam foundations so in this case this house actually had a perimeter beam but oftentimes you'll just see these right here this is a pier that's been poured and then the guys are gonna put a sauna tube on that he's actually vibrating that at the end and make sure that concrete is gonna be nice and aerated or we're getting the air bubbles out of that you can see there's a rebar cage in this case that's going down into the earth and in this case we actually had to drill down until we hit rock so we went pretty far down then he's gonna level that off and we're gonna pull those forms off and here's that foundation as we're getting ready for framing now again this is this blue that you see here is going to end up being a vapor barrier so we've actually taped that to our piers here and we've run it up the sides of that perimeter beam on the outside but what's going to happen that you're gonna see in a minute here is we're gonna bring our framing and it's gonna sit on top of these and form that grid work of the house on top okay so I skipped a step here on top of the blue vapor barrier in this case we poured a small slab which is basically a concrete sidewalk just a couple inches thick no rebar just a mesh down there so that when we finished this pier and beam house we're gonna have a really nice crawlspace and you'll notice that perimeter beam that's running all the way around the outside that's gonna form for this house a condition to crawlspace now there's two types of crawlspace is a vented in an unvented crawlspace this will be an unvented crawlspace which in effect is a short basement again we've got rock we've got all kinds of other reasons in Texas while we don't need foundations also we have a very shallow frost line in fact most parts of Texas don't have any frost line whatsoever so as a result we don't need to dig down and so this crawlspace is going to end up acting like a shore basement on the house and here's what it looks like just before we start the framing sorry I've got my photos that order here we go so here's the crawlspace now we put this black down just to keep the construction debris off of our basement concrete slab so that's just a protection layer for construction that will get removed later but now you can see here's the beams or yes here's the beams that are going to run on top of the piers right here and what you're seeing here is that good work is then going to get filled in with in this case I joist now once the I joists are in place because this is a conditioned crawl space we're going to run the perimeter of the floor and on that perimeter we're running inch and 1/8 Advantech and you're gonna see why we only did the perimeter here in just a moment now here's that inch 1/8 Advantech right there and you can see what we're doing now is we're forming that short basement by putting two inches of closed-cell spray polyurethane foam on the whole outside perimeter of this conditioned crawl space so now that short basement is going to be air conditioned and I don't need any insulation in the floor line because it's just going to be on the perimeter of this house so now we're ready to go into framing now that that's complete we can finish that floor and move from there up but in this case so now we've got a pier and beam with a conditioned crawl space ok now let's take a look at the other type which is an unconditioned crawlspace this is a house that we did a couple years ago that's a modern farmhouse style in fact I created this house with starting the modern farmhouse movement but this is a house where the owners said to us we're really interested in the potential of being able to move this house they'd move from a country farm that had a house moved on to that site and they said look we want to build a new house on this farm site this is actually the Springdale farms house here in Austin Texas and we may in the future need to change the way the land is used and we want to be able to move the house either within our current property or some day if we sold the land we might want to actually move this house off the property and that's where a pier and beam house absolutely shines so here's the underside of this house now this is a this is going to be a traditional vented crawlspace so here you can see our piers right here and you can see daylight from this photo I'm under the house looking underneath the house and we just have piers in beam intersections and then in this case we use the more traditional lumber we actually have two by tens and two by twelves for beams and for floor joists in here so this is a much more traditionally framed house really this this house built I guess we finished this six or seven years ago has built the same way houses might have been built in the 1950s in Austin Texas with the addition or the change that underneath that crawlspace we use closed cell foam and sprayed it up underneath the floor joist and spray the whole underside of the house here's the finished house now that it's done now what is it about these houses that I like pier and beams there's several things I like that pier and beam houses are easier to insulate slab on great houses really can't be insulated very easily there's some perimeter insulation you might use there's a few other tricky ways but Piron beams in the other hand much much either easier to insulate either we can do an unconditioned crawlspace and insulate the perimeter of our short basement or we can spray foam underneath that there's also batt insulation that could be used it's a little bit harder to get it right but in general much easier to insulate and now you've got a fully insulated floor the other thing I really like about pier and beam houses is they're much easier to fix repair upgrade and remodel remember that picture I had at my friend's house this is the one that had the no p-trap you can see that pipe there was connected to that no p-trap super hard to diagnose the problem it's not like we could get under the house and have a look where as if this was a pier and beam house we could have crawled under there to really see what we were getting into we could have fixed that same day really in this case we had to demo all the tile we had to get rid of the concrete huge amount of work to do it much much harder to diagnose much harder to repair to Rema to upgrade another big benefit of pier and beam houses is they're actually easier on your feet I'm saying that from my concrete slab here that I'm talking to you at my shop but if you stand on concrete all day long you'll notice that your joints feel tired there's no give on that concrete so you're relying on your shoes and that cushioning in your shoes to cushion that but when you've got a pier in beam house that wood has a little bit of give so as you walk the floor flexes just a little bit now you don't want it to flex so much that you're shaking your grandmother's china cabinet when you walk by but believe it or not there is a difference on your feet and standing all day long on a pier in beam house wears a slab Alice I guarantee you're gonna notice the difference and the other thing that I mentioned earlier much much easier to move that house someday if we want to this farmhouse as I mentioned that has this Piron beam if that client wants to move that someday all they're gonna have to do is cut all the plumbing off cut the connections between the concrete piers and the wood framing slide some I Joy's under there and Jack those up and literally that house could be moved on a semi and put on another location anywhere in Texas or anywhere in the world for that matter because you literally could pick the house up you cannot do that with a slab on grade house you're you're very very limited when it comes to remodel time guys thanks for joining me on this deep dive on Foundations as you can see I really like pier and beam foundations however there are times when slabs are absolutely the right choice it's going to depend a lot on your conditions on your soil on what the engineers say so definitely get a soils engineer involved so you know what the ground is that you're putting your house on and you want to consult your structural engineer as well as your builder before you build these you don't want somebody who's never built one of these foundations before they're only doing this one type and you're forcing them to do a different type but if you have the options as you can see I really like pier and beam houses and I like them with a condition crawl space underneath guys if you're not already a subscriber hit that subscribe button below we've got new content every Tuesday and every 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Channel: Matt Risinger

Views: 1,134,343

Keywords: concrete house foundations concrete foundation pier and beam

Id: q4nGeEOXm8k

Length: 19min 2sec (1142 seconds)

Published: Tue Jul 30 2019