Concrete Slab Insulation MISTAKE

www.AsktheBuilder.com founder, Tim Carter, shares mistakes made with concrete slab insulation. Tim does phone coaching: shop.askthebuilder.com/consul...

[@DCampanella-kj5sx]

Thanks!

[@askthebuilder]

Many many thanks for your support of my channel!

[@eveadame1059]

​@@askthebuilder Won't the gravel poke holes in the barrier? And won't the foam board float if cement is poured, directly onto it? It seems like the foam board, should be laid down first, with the barrier laid on top of it

[@yodaiam1000]

A lot of places put the vapour barrier on top of the insulation so it just might not be installed yet. Doing it that way, allows water to drain from the insulation. Otherwise, you can get thermal drift (the insulation becomes less effective). The built-up plate is definitely wrong. You don't put wood below the level of the concrete. It will get soaked and rot. Even if it doesn't rot, each of those plate will shrink and cause issues along the wall that is over the plates. The right way to have done that was to pour the concrete foundation wall higher. If they left it low by mistake, you can always por another short wall over the lower concrete.

[@dsm9785]

You said what I was going to say, 👍👍

[@joses8168]

Some people might say put the moisture barrier above the foam. So the concrete does not get between the foam and moisture barrier!!! 🤷🏻

[@stevecrawford6958]

the moisture barrier does go above foam, if using foam. unless you are doing a super-humid space (pool/steam room for example)

[@matthewlucas7078]

Keep this series going! Can't wait until heavy rain and winter.

[@askthebuilder]

Matthew, TNX. If you want the series to continue, I need your help and that of THOUSANDS of others. Do you know what I make from ad revenue from each view? $0.006 Do the math. $6 I need you and many others to click the *THANKS* text link and help me get more HELP to do more videos faster.

[@mikebennett4922]

In the UK they allow your dpc visqueen barrier 1200 gauge to go over or under your 100mm rigid insulation then turned up any wall the thickness of your concrete slab or slightly higher maybe up to dpc level this usually applies with a double brick/block wall with a 100mm insulated cavity but any internal length of outside wall fit a cold barrier upstand of 25mm thickness insulation the thickness of the concrete before laying to obviously stop cold penetrating from your outside wall into the new concrete slab

[@kenguyer1897]

You’re correct on the built up sill plates and that’s a shortcut way of correcting their mistake. For sure will cause issues down the road, but the vapor barrier goes on top of the foam for multiple reasons.

[@askthebuilder]

Agreed to a point. The closed-cell foam is a very good vapor barrier. Remember, I didn't build this house.

[@3charliewright]

The vapor barrier is not installed yet. It goes on top of the rigid from insulation. They will put it on later. As far as your comment about pressure-treated plate the only one that should be pressure-treated is on touching concrete. The top one doesn’t need to be pressure-treated.

[@sobladitsgood3917]

Hi! Love your channel! Isn’t there also an issue of frost getting through the concrete wall and freezing under the foam since it’s a slab on grade? Or is that not a concern. I worry about since the building heat isn’t transferring down due to insulation in floor, it could freeze and heave underneath.

[@askthebuilder]

TNX. Insulation *SLOWS* the transfer of heat. The heat from the house gets under the insulation and into the gravel. Conjure up all those high school physics classes. You were probably one in the room that said, "How will we EVER use this information in our lives????" Now you know!!! :-)

[@Mark-eu4di]

Great channel! Love your shows, as a licensed electrician I’m not up on concrete codes but is a vapor barrier required in all states of the US?

[@askthebuilder]

Mark, TNX. The big difference between the NEC and the building code, I *believe*, we builders use is that local inspectors use the building code as a set of recommendations. They can ignore parts or even make it more strict. The NEC, as I have seen, is the law of the land and local inspectors have no, or minimal, leeway. Bottom Line: Even if vapor barriers ARE in the code it doesn't mean a builder has to use them. But those that don't obviously didn't pay attention in high school physics class or were absent on certain days.

[@Mark-eu4di]

@@askthebuilder thank you for that quick response! Most basement slabs that I have seen use fine sand, then tamp it, install a wire mesh then pour. I don’t believe I have ever seen pvc pipes placed to draw out radon gas at all sadly. Just for French drain systems near high water tables. I’m wondering why this isn’t mandatory? Similar to leaching fields used off a remote sewer plant…

[@askthebuilder]

I'd rather not state in public why I think it's not mandatory.

[@Mark-eu4di]

@@askthebuilder I understand and I’m sure it’s a cost factor that no one wants to pay for or even knows about (meaning the homeowners).

[@askthebuilder]

No, that's not the reason at all. You're not even close. Clue: Who authors the code? Any homeowner that was given the option of installing a vapor barrier assuming it was explained WHY it's so important would undoubtedly say "install it". The issue with slabs is you get ONE CHANCE.

[@jamessiedjak5868]

The KZbin app on my Android phone doesn't have the thanks option that I can click on. The app is the latest version.

[@askthebuilder]

You know what to do, right? Let me know what KZbin support says when you tell them that you want to HELP a Creator with a donation, but you're unable to do it.

[@rafirk7968]

What insulation would you recommend under the slab and can I put 1” insulation?

[@askthebuilder]

closed cell foam. You can put anything in you want. If you need detailed help, I can offer you my protection: shop.askthebuilder.com/15-minute-phone-or-video-conversation-with-tim/

[@freedomofreligion3248]

Why didn't they TAPE, with top quality tape, the perimeter + all the seams?? And, they must put the hardwood perpendicularly to the long sides of the foam. If they're simply going to pour on top of this, he's totally right.

[@askthebuilder]

Contact the builder of the home for your answers. It wasn't me.

[@user-zy9xy4ru3f]

spray it with foam!

[@Brandon-no3vc]

maybe theyll put the barrior ontop

[@askthebuilder]

They didn't put any additional vapor barrier down.

[@StringBanger]

@@askthebuilder Not even on top of the Rigid Foam? Some install gravel, then foam, then a 6 mil vapor on top of the foam

[@cynthiaarmstrong7972]

The vapor barrier belongs on the top of the insulation, not under it

[@AnthonyJennings7]

@@cynthiaarmstrong7972 Yup, otherwise the concrete would get under the foam boards and pop.