Slab-On-Grade INSULATED Foundation - Part 1

guys if you've been watching my channel you know that i'm a huge nerd when it comes to insulation and air sealing but on this video i'm insulating in a place that i have never done before that's right on top of the slab we're going to be putting an inch and a half of insulation down and then subfloor on top of that i've been thinking about this detail for a long time and i've seen it in the north but as far as i know this may be the very first house in all of the south that's ever gotten this detail today's build show all about slab top insulation let's get going [Music] all right guys let me set the scene here so this is a 1970s house so this slab on grade is an existing slab on grade but this might as well be new construction all the walls basically from the foundation up are all brand new and i think you could do this method also on a brand new slab now what we're doing is we're using an inch and a half of this this is a four by eight sheet of foam it's made by logic brands this is their halo interra and this happens to be gps foam graphite polystyrene it's basically impregnated with graphite basf i believe owns the patent on this and it's called neopor and so this graphite polystyrene around r5 per inch so i've got an inch and a half is going to provide a continuous r5 on top of my slab now i say continuous but there are a few breaks and you'll notice i've got some walls framed already and those walls go down to the slab what we've done is all the perimeter walls obviously are bearing right onto the slab but these interior walls that are load bearing we framed ahead of time now you notice this wall is not here this is actually going to separate eventually this family room from this master closet there's a bunch of walls missing here there's a bunch of walls missing here those are all non-load-bearing walls now if you were designing a new house like i've seen steve basic do in fact this is his this is his design you could actually frame a new house or design a new house so that you'd have nothing but exterior walls and no interior load bearing walls and then you'd have an even better thermal break on top of your slab so i've got a little bit of a break but this is going to provide me a lot of insulation now why would you want to insulate your slab we see insulated slabs all the time in the north basements are insulated for instance so that concrete basement floor will have several inches of thick foam underneath it that's floating the concrete is basically floating on top of that insulation and it's pretty normal to see that in the north everybody knows oh my basement's cold that floor is going to actually pull the heat out and couple that to the earth because the earth is you know maybe 50 some degrees constant which means that if you're heating if you're in the winter wintertime you're trying to get warm this concrete is pulling that heat off of you now in the summertime there could be some benefit to having a ground coupled slab but i would say that when we insulate our walls and our roofs that's insulating for both heat and for cold right in the summertime in texas it's hot out those walls are stopping that flow of heat from my cold house to the outside in the winter the opposite is true that insulation is keeping the heat inside my house as that heat's trying to go through my walls and get to the outside heat is always going to move from more to the less just like moisture is always going to move from more to less okay so let's get to a couple of details now most of the time when people are doing concrete slabs and they're attaching let's say hardwoods on top of that slab there's a couple of methods you could use a engineered floor like this one which is going to have a plywood core and you could probably glue this floor in many instances right onto a concrete slab but in custom homes it's pretty traditional in the south to see something like this just a little mock-up of a sleeper system and in fact i did a similar system to my house 15 years ago when i remodeled where you're going to use a vapor barrier then you're going to use some pressure treated sleepers these are two by fours that have been pressure treated and then you're going to attach plywood on top of that or subfloor and then you're going to add your hardwood floors on top of that the benefit of this is it's going to give you a little bit of give under your feet said no one ever oh i can't wait to stand on my concrete floors for 10 hours on the other hand houses that have joists crawl spaces or basements that little bit of give in the wood with that air gap under there means that the house is much more comfortable on your knees and i would say that's a huge reason to think about this insulation system we want to make sure that we don't get any water in this area that could be a really big problem so we've added a few floor drains in a few places but you're going to notice one beauty of this system is that floor drains or electrical conduit is really easy i actually didn't need to auger out my concrete all i had to do was make a spot that's a little lower for my p-trap so in this case this p-trap that you're seeing here is an emergency drain for the dishwasher this dishwasher the kitchen sinks by that window right there the dishwasher is going to be right here we'll cut this flush later and we'll add a pan for that dishwasher and then this will be an emergency drain we'll fill that p-trap with mineral oil that way there won't be any soil or pardon me that way there won't be any bugs or air infiltration coming up through and i don't need to worry about that connecting to my sewer system either it's just running straight out of the house now this is this drain's going to come up a little bit when i put my three-quarter plywood on i'm going to probably just make a three-quarter plywood break here and then the top layer will span over top of that but you'll also see we did the same thing with our conduit this is a future island plug in the kitchen and we used one inch conduit so this is basically just below or flush with the top of my foam and then i'll in fill this with pieces of foam and then when we come in and do the subfloor in another day or two all the subfloor is going to do is basically just float over this like a big raft in this wild it's a really fun concept i've thought about this for a long long time so i'm finally excited to actually do it on a job all right guys day two on day one we pretty much got the entire foam down on this 2400 square foot house and then towards the end of the day we started laying our first layer of advantech this is going to be forming the basis of our floating subfloor on top so i think one of the questions you may be asking is if i could i do just one layer and this i think will explain why you don't want to do just one layer because we want that stiffness we want this raft to float over all the top of the insulation and then ultimately that concrete and just as a reminder that insulation is not glued or bonded in any way to the concrete below it's just loose laid basically when the guys came in they just loose laid it all the way over the top and then they came back and taped the seams we taped the concrete to the bottom plate with some sega resam tape that's that green tape you saw in the whole perimeter of the outside now that had two purposes i've started using that for air tightness because it's a really good way to make sure air and bugs are not getting underneath that bottom plate i'm a big belt and suspenders guys so i like to do more than one method actually here's a roll of that tape right here this is that rissan tape and they sell this in 60 100 and i believe 150 millimeters which is basically equivalent to two four and six inches in width now between the concrete and the bottom plate i used the real wide model i think it was the six inch the 150 millimeter and i used the primer so it would really stick now this tape is expensive it's somewhere around maybe 25 30-ish bucks a roll but man you pay for the good stuff you buy once you cry once it is really good and it stays stuck tenaciously and remember this is going to be buried in that wall for the life of the house so it's worth spending money there however for this detail you don't necessarily have to do that now for the second time i put a tape down is the perimeter after the foam goes down and i did that to make a continuous vapor barrier the top of that foam has that kind of metallized plastic sheet on it and that's going to be forming the basis of the vapor barrier especially when i tape that and i've and now i've got this continuous vapor barrier i want to tie that into the walls to make sure i don't get any vapor on the top side the big reason to do that is not necessarily for the advantech this is a pretty stable product but when i put hardwood floors over top especially if my client opts for a solid hardwood floor i don't want any of that moisture coming up and causing my hardwoods to cup or move all right let's get back to the mechanics of how this works you saw a second ago the guys were using this right here this is a spray polyurethane foam glue or polyurethane glue i should say not spray it goes out like this and these cans last a long time when you're using them on standard eye joists they go a little bit quicker we're probably using about twice as much as i originally expected quantity wise i think we're going to end up using around a dozen to maybe 15 cans for this 1500 square foot house we're running that out in a serpentine fashion and then when they put that sheet down what's going to happen is they're going to screw that down now they're screwing that down with some screws that are not going to penetrate the foam they're only going to screw both sheets of plywood to each other so i'm using the pam fast system from fasten master that's that gun you saw chewie using earlier that's the stand up screw gun and as he stands up and screws those down ultimately what he's doing is not so much attaching as clamping right that polyurethane glue is amazing and that's one of the secret sauces to make advantech so amazing this is an oriented strand board product but with that polyurethane glue and i don't know what else they're doing to make it moisture resistant some other secret sauces but that polyurethane glue in the sheets bonds to the polyurethane glue that we're bonding down and once we screw it it's basically clamping that wood together okay so then once they nail those together you see they're using a uh a hammer here pardon me a sledge rather and all they're doing is just bringing the seams together now you want it tight but not too tight follow the manufacturer's best practice wrecks because you don't want to slam it so tight they're perfectly tight the other thing you're going to notice on the perimeter like right here is we've spaced the advantec off the wall i just used a piece of hardy on the outside there i'm looking to get somewhere between uh around 3 8 of an inch maybe as much as a half gap this is probably a little bit more like a quarter but that's okay too we want to make sure that if there is any movement expansion contraction on this raft that it's not pressing against our exterior walls that would cause some buckling so we always want a little bit of space in there as well okay the next thing to notice on this as they're laying these sheets look how this first sheet is oriented against the back wall of the house and then the next sheet right here is totally offset on the uh on the seams right so now we're running 90 degrees from this first sheet so it's running front to back whereas this one was all the way off the back of the house and then we've ripped the sheet so like you can see this last piece that's going in here here's one four by eight sheet that way one four by eight sheet this way and we're spanning that with this last piece so none of the seams want to line up it's really really important to not have any of your seams line up on this floating raft and that way we're spreading that load out you know with one sheet on here as i walk on this foam i'm putting more of a point load on that particular piece of foam that i'm stepping on but as i get that second layer of advantech on top of the first layer it's spreading my load out even more now let's talk for a minute about the psi rating on this foam this foam is not a particularly crush resistant foam i've only got 10 psi foam here and the guys at inter or halo in terra which is a logix brand they make 16 psi foam now i originally thought i wanted that 16 psi foam but as i talked to their tech department and thought about it a little bit i realized you know what i don't need that let's think about this for a minute if this is 10 psi foam that's 10 pounds per square inch so if i have a point load yeah it only takes 10 pounds to push that foam down but in a one square foot that's 144 square inches multiply that by 10 that's 1400 pounds per square foot so as i stand on this floor in this you know in this one square foot section even if i'm a 500 pound man which i'm not i weigh you know 190 pounds i'm nowhere near the loading capacity of this floor and remember because i've got that thick floating raft i've really spread out that load so like at my house i'm going to be using the same method i've got a piano in one spot i've got a gun safe in one spot but i'm not worried about those loads because they're going to be spread out if you were worried about that if you had an elephant living in your house you'd want to go to a higher psi phone but in this case i'm good to go now a couple things i want to uh to mention when it comes to the mechanics again of this install you'll notice in this area where the guys are working it's wide open there's really no walls in that spot but i've got a wall here and i've got a wall here let's back up and i'm going to show you what's going on with that and why so if you look up right here look at that roof line right there see those angled beams right there that's called a strong back and that's carrying roof load the engineer has designed those two by sixes to bring some of that roof load down those rafters are going from that ridge which is way up there and that two by eight or two by ten i'm not sure which it is goes all the way out and sits on the outside wall that's a long span so the engineer has designed that strong back and that strong back is angled and now sits on this 2x4 wall so in other words this 2x4 wall is a load-bearing wall if uh if you're watching this and you're remodeling this house in 40 years don't remove that wall that's a bearing wall so what we did was we framed the bearing walls down onto the slab but then we've not framed the interior walls now had i thought about that before i probably would have designed the house with loads only on the outside walls because then i could have had nothing on the inside breaking that thermal bridge right i'm going to have a little bit of thermal bridging happening at those interior walls but in the scheme of things not a whole lot and this may be as far as i know the first house in the south or certainly in texas that's gotten this insulated on top uh design so you know live and learn i think i would do this slightly differently next time but if you followed steve basic's work before an architect out of massachusetts he's on my build buildshownetwork.com he and steve did a house in missouri that i saw that had roof trusses that sat on the front the back and i was in a house with a similar design to this no interior bearing walls whatsoever and now you'd have a fully continuous so if i would have thought about this a little earlier in the process i might have but again this is also a remodel underneath my feet here is 1970s concrete this is the original slab on the house and then we framed basically a new house in the same shape as the old concrete okay let's talk about cost while the guys are kind of making their way down here cost is it always an important factor and i know i get i get gigged a lot in the comments on cost this is more expensive but it's in my mind not prohibitively more than what is kind of the standard method now earlier in the video i showed you what the standard sleeper system would look like in fact i've done that on lots and lots of houses including my own house that i i remodeled 15 years ago that sleeper system typically you're going to see two by fours this queen and maybe a single layer of three-quarter advantage let's think about those costs three-quarter advantage in my market in today's prices around 40 bucks a sheet ish mossy menos i remember prices change over time so if you're watching this later it may change but around 40 bucks a sheet two by four pressure treated right now i would run those on 16 inch on centers it's about eight bucks uh nine bucks something like that for a 10 foot two by four pressure treated in my marketplace and if i run those on 16 inch centers if i add in the cost of the 2x4 the visqueen and the advantek the three-quarter advantek to do a four by eight section so 32 square feet we're talking about maybe 60-ish dollars in materials something like that in this method let's talk about how much this costs those four by eight sheets of interra foam that you saw from halo that's a inch and a half thick r 7.5 that runs about 20 bucks you might get it slightly more slightly less about 20 bucks a sheet and then as i mentioned i've got two layers of three-quarter advantage so that's forty dollars a sheet times two about eighty bucks so i've got about a hundred dollars per four by eight sheet into this design right here labor i've got four guys working on this project and it's going to take them about three days to do this insulated subfloor and uh floating um insulated slab detail basically so you have to kind of add that up in your marketplace the tape you probably could use a less expensive version of the tape and you wouldn't necessarily have to use the seaguar resan to air seal although that's my favorite detail you could get away with the less expensive tape so i'll leave that off for the moment so we're talking about 350 ish 325 per square foot for material costs and then you got you need to add your labor on top of that that could be anywhere from a dollar to maybe two dollars more per square foot so this is a 2400 square foot house right so we're talking about you know maybe seventy five hundred dollars and eighty five hundred dollars in materials and then a little bit more for labor but what i like about this detail is now i'm ready for my hardwood floors or whatever i could also run tile on top of this now if i run tile though i need to remember this floor has some give to it i'm going to want to put an uncoupling membrane down like a schluter ditra or at a minimum at least a hearty backer type material a scent cement board before i put that tile down on top of this but if i'm running hardwoods nail down glue down whatever right on top ready to go all set now let's talk a little a little bit about the advantages now i talked about this earlier the big advantage obviously is the thermal break and the comfort that you're going to get especially in the winter time on a house like this because now my feet my bare feet aren't touching bare concrete that are sucking that heat out of my feet anymore instead i've got that insulation and i've got that plywood or that advantech underneath me which is going to be basically the same temperature as the rest of the house that's huge but here's the intangible that you can't really account for for comfort and that's this right here you know i'm almost 50 years old my knees get tired really quick after standing on concrete at my age and i'll tell you the difference between this floor and a concrete floor night and day this is like standing on one of those stand-up work mats you see at factories around the country on top of their concrete floors it has just a little bit of give not that much as a stand-up ramp right but enough give that it feels really comfortable i think that forgiveness is really the hidden gem that no one thinks about that cushion that softness underfoot that's something that's intangible you can't quantify that it's really hard to sell a client on comfort and yet i do it all the time because my houses are vastly different they're more expensive they're built better but they're also quite a bit more comfortable than a standard build house appreciate you guys following me and your support out there if you're not currently a subscriber hit that subscribe button below we've got new content here every tuesday and every friday follow me on twitter instagram otherwise i'll see you next time on the build show [Music] you

Channel: Matt Risinger

Views: 171,550

Rating: 4.9374332 out of 5

Keywords: Matt Risinger, Build Show Network, The Build Show, Build, basement insluation, slab insulation, best concrete insluation, best insulation matt risinger, foundation, Insulated Slab, Slab Edge Insulation, How to Insulate Your Foundation, Basement Insulation, Insulation, Slab On Grade Insulation, Best Foundation Texas, Best Foundation South

Id: 8SSG2AofIe8

Length: 21min 44sec (1304 seconds)

Published: Tue Dec 08 2020