Basement subfloor questions

Bud Cline · 10-12-2010, 04:44 PM

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Isn't it possible to waterproof a slab at the time it is poured either by putting a vapor barrier below it or laying out a barrier so it lies midway within the slab?

Moisture barriers below a slab have their issues and questions as to their life-expectancy have arisen over the years. Some of that poly is biodegradable over time. Some guys swear by the process and others wouldn't touch the idea with a ten foot pole. I suppose region of the country also enters into it.

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Isn't it possible to waterproof a slab at the time it is poured either by putting a vapor barrier below it or laying out a barrier so it lies midway within the slab?

Never heard of that! That's not to say it may or may not have some merits. Sure would change the definition of "monolithic".

This kind of stuff is really arguable in a place like this.

I have my own thoughts on the subject but that doesn't make me an engineer.

acerunner · 10-12-2010, 04:46 PM

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Originally Posted by Bud Cline

NO!

Boy, that'll get an argument going I suppose!

Basement concrete floors are always susceptible to rising moisture. Moisture is always present to some degree. A natural phenomenon is for moisture of this type to seek evaporation. To evaporate, it must rise. Trying to seal it [in] isn't at all practical in most cases. For long lasting results without mold and mildew a floor must be allowed to breathe (evaporate). Tile is the most practical application for the promotion of overall uniform evaporation of the substrate.

If a tarp left on the floor has resulted in moisture on the tarp, then there is moisture in floor.

that's what i thought. But if there's a way to control the path at which evaporation occurs. For example, as rustybaker states, moisture will gravitate to the edges, so you can then vent moisture away there where it would be much easier to do that when moisture is coming up through out the floor.

as for tile. I'm not convinced thats a fool proof solution. Over the weekend, I pulled up the tiles in my foyer that was laid directly on concrete (slab on grade). A lot of it was very easy to pull up because the mortar had become separated due to mold.

Bud Cline · 10-12-2010, 05:06 PM

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For example, as rustybaker states, moisture will gravitate to the edges, so you can then vent moisture away

Yow-well, good luck bringing that theory to fruition. Rusty is correct but what happens to the moisture as it is en route to the edges? The substrate turns into farmland - that's what. A perfect place to grow crops of fungus.

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as for tile. I'm not convinced thats a fool proof solution.

It is the only fool proof solution. Evaporation would be naturally occurring throughout the entire area through each and every grout joint. Are ya kiddin' me?

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Over the weekend, I pulled up the tiles in my foyer that was laid directly on concrete (slab on grade). A lot of it was very easy to pull up because the mortar had become separated due to mold.

No-no-no-no-no!

That's not how it works. The mortar had become separated for other reasons giving mold an opportunity homestead the voids. There are any number of reasons why the mortar may have separated but mold isn't one of them.

Bud Cline · 10-12-2010, 05:07 PM

By the way......
Your front door has a leak. I can see it from here.

acerunner · 10-12-2010, 05:20 PM

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Originally Posted by Bud Cline

Yow-well, good luck bringing that theory to fruition. Rusty is correct but what happens to the moisture as it is en route to the edges? The substrate turns into farmland - that's what. A perfect place to grow crops of fungus.

U are right, it is just a theory i was curious about. I will likely have many questions & theories as I try to understand the whole issue of moisture-concrete-flooring.

Relating to moisture enroute to edges, is that not the same idea behind tiles? What happens to moisture under the tiles enroute to grout lines? Shorter distance, true, but still traveling in the same form, whether it be moisture in a vapor phase or liquid phase.

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Originally Posted by Bud Cline

No-no-no-no-no!

That's not how it works. The mortar had become separated for other reasons giving mold an opportunity homestead the voids. There are any number of reasons why the mortar may have separated but mold isn't one of them.

what are some reasons, and how can they be prevented? I plan on retiling that area, so i'd like to know what to watch out for.

acerunner · 10-12-2010, 05:23 PM

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Originally Posted by Bud Cline

By the way......
Your front door has a leak. I can see it from here.

quite possible, but not sure that's the reason.

The front door is inset from the front face of the house. The door never sees rain directly.

Bud Cline · 10-12-2010, 05:29 PM

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Relating to moisture enroute to edges, is that not the same idea behind tiles? What happens to moisture under the tiles enroute to grout lines? Shorter distance, true, but still traveling in the same form,

OK, now you are over-analyzing this whole thing and maybe yanking my chain just a little.

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what are some reasons, and how can they be prevented?

Use a better quality tile thinset mortar next time and this time follow the directions on the bag.

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The front door is inset from the front face of the house. The door never sees rain directly.

And I suppose the wind never blows either!

acerunner · 10-12-2010, 05:43 PM

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Originally Posted by Bud Cline

OK, now you are over-analyzing this whole thing and maybe yanking my chain just a little.

I'm not yanking your chain, at least not intentionally. Yes I admit, I do tend to over analyze things. I like to understand the science of things. articles on buildingscience.com are the type of explanations that get me to go "Ooooh, i get it now". There was one article on this topic that said epoxies or dimpled membranes are "bullet proof" solutions, and tile & grout is a good solution but will not work on slabs with high vapor emissions. Of course science lab results and real-world results do no always match, so I'm curious what you think.

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Originally Posted by Bud Cline

Use a better quality tile thinset mortar next time and this time follow the directions on the bag.

Tell that to the previous owners or contractor.

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Originally Posted by Bud Cline

And I suppose the wind never blows either!

It's inset maybe about 6ft. Even on the windiest storms, the bottom of the doorway barely gets splashed.

57_Hemi · 10-12-2010, 09:33 PM

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Just a question regarding this. Isn't it possible to waterproof a slab at the time it is poured either by putting a vapor barrier below it or laying out a barrier so it lies midway within the slab? I'm thinking that the slab might suffer weakness with the barrier imbeded within it, assuming it can be done.

That is a good question..........

Bud Cline · 10-13-2010, 12:27 AM

That may be a good question but Bud Cline didn't make that post as it appears above. That question was asked by someone else and mis-quoted in the above post.

57_Hemi · 10-13-2010, 08:06 AM

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Originally Posted by Bud Cline

That may be a good question but Bud Cline didn't make that post as it appears above. That question was asked by someone else and mis-quoted in the above post.

DONE!!

Dont worry........ WE KNOW that U KNOW what ur talking about.

(I quoted from a post that had quoted you first. Therfore your name was posted up top......

)

acerunner · 10-13-2010, 03:07 PM

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Originally Posted by Bud Cline

That may be a good question but Bud Cline didn't make that post as it appears above. That question was asked by someone else and mis-quoted in the above post.

so budcline, what is your opinion on that question? I have my theories on it, but since all my theories have been shot down, I'm curious to know what you think before I answer.