Quality House Foundations: Avoid Structural Problems

hi guys Michael with armchair builder comm here it's so important to get the foundation for a new home right that we're gonna take a deep dive into what quality features are needed to avoid problems if we get the foundation right it will last for generations get it wrong and your new home foundation can be an expensive headache for as long as you own the home so there are three critical components to a home's foundation and those are the soil beneath that supports the foundation the waterproofing and drainage that surrounds the whole foundation and then lastly the foundation structure itself now because these three components are so complicated we're going to cover them in a three-part video series today I want to share with you the first part of the series the foundation structural engineering for a new home with a basement I will share with you some best practices that will help keep your home's foundation free of structural problems and basement water leaks the foundation is such a critical element of any home not only does it support the entire home in its contents but it also houses everything in the basement things like hot water heaters furnaces laundry appliances are expensive items that need to stay dry on top of that many of us will finish the basement at some point in time so it's imperative that the foundation does its job so let's take a look at the engineering behind a quality poured concrete foundation so here's a quick look at what the foundation looks like after it's been poured you can see the brick pattern in there and also the footing sticking out below the wall down there that's supporting the wall the brick pattern is because they used those brick forms that have that pattern in them first start by showing you guys the anatomy of a typical poured foundation concrete wall system here and this is a cross-sectional view so if you cut the house in half this is what it would look like we start with the footing which in our case for the open-book build was 16 inches wide and 8 inches deep and then the second pour that's poured first then the wall is set up on top of that the forms and we pour that for our case we went with a nine foot tall wall because we're going with a finished basement in the future and we wanted plenty of headroom to make it feel like the traditional you know living space that wall was eight inch is thick nine feet tall and then later on we come in and pour the basement floor which actually rests on that little ledge here that's left over four or five inches of foundation footing and so when anyone quotes you a nine foot tall basement wall you have to subtract that four inches for the basement floor to get the head height from the top you never be standing on top of this basement floor down there when we're finished here you can see we're actually using a pump truck to put concrete between the forms there to go ahead and get those filled in so then we can level it off and and then let it set up bring you the forms and then build the foundation walls on top of that so we put three strands of rebar seen in this photo here in the bottom of these footings to give it support along the full length of the footing so here's a look at it shooting down through the footing forms and kind of what that looks like before we pour you can see the rebar three strands along the bottom of the footing there the lengths are tied where the ends of the rebar are see these ridges in the rebar that grabs on to the concrete so if they were smooth they wouldn't hold on as well so the concrete's gonna go around those rebar and it's gonna really latch on to it with those ridges to really give it strength these chairs are here that black chair holds the rebar three to two three inches off the ground which gives it maximum support and then you can see these nails right here show where the top of the footing needs to be poured to to be level we want to make sure this footing is level because everything above that builds off of it so with the footings level the wall foundation wall will be level and then the framing will be level so really important there so here's another cross sectional view of the footing with the three strands of rebar in the bottom so here's a quick look looking from the outside of the foundation at the foundation wall in footing now this is a little bit of an exaggeration but you can see this void created here on the right side under the footing where their settlement taking place in the ground beneath the footing and what happens is if there's no rebar in that footing it wants to settle and this settlement can lead to cracking in the footing and the wall above and eventually potentially settlement in those where they actually moved down creating a structural problem for this house so the three strands of rebar in the bottom of the footings are a best practice and this is probably a good time to say that not every crack in the foundation wall is a structural problem when you want to be concerned from a structural standpoint as if the crack displaces or moves and this can be in the form of a vertical displacement as just mentioned with settlement or it can be in a horizontal displacement and remember any kind of displacement in a wall crack can cause a breach in the waterproofing membrane which can lead to water leaking into your basement which we obviously do not want so now let's take a look at the engineering behind the poured concrete foundation wall we're placing the concrete between the forms here and once everything's done and we're ready to backfill our excavation contractor starts to fill in around the foundation and this starts to put a lot of pressure on that wall you can see here the arrows indicating the pressure on the outside of the foundation wall which wants to bow that wall in so in order to counteract those forces we put steel rebar in the wall and these are the vertical rebar every three feet along the length of the wall from the footing we also put horizontal rebar in the wall it's hard to see here but they're sticking out one in the lower third middle and top of the wall where they're forming up here so here's a plan view of the foundation wall from looking at it from the outside the footing in the wall here and you can see the vertical rebar every 36 inches along the length of the wall number six rebar and then we've got these horizontal rebar one at the top third one in the middle and one in the bottom third that works like kind of like a belt on a pair of pants holding everything together on this wall so that we really have a solid wall that's going to hold together and counteract those forces from the outside so they're critical pieces of that foundation wall pores making sure they don't leave any voids in it so we wanted to be one solid mass so any kind of voids will create a weak spot in the wall so they're very careful at placing that concrete to make sure that all of the gaps between the forms are full so another best practice guys for foundations is to use a minimum design strength for the concrete of the footings of 2500 pounds per square inch and then for the walls design strength of a minimum 3,000 pounds per square inch so that does it for house foundation engineering we'll be posting to other very important parts to this video series in the coming weeks which will cover the soil below the footings and the foundation waterproofing and drainage systems around the foundation if you need more information about building or repairing your home stop by and see me at armature builder com thanks for watching

Channel: Armchair Builder

Views: 237,982

Keywords: House, Foundation, engineering, Avoid, Structural, problems, quality

Id: EYUe_NIoTbE

Length: 7min 26sec (446 seconds)

Published: Fri Jun 12 2020