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Discussion Starter · #1 ·
Rarely post, but do lurk and gotta say a great resource. Prior to posting I did search for this specific problem and missed anything that might address my dilemma....

I'm hoping to get a conversation going on how to create an air flow and space that will allow moisture to dry/escape inside finished interior space where an exposed footing and trough are subject to regular bouts with water infiltration.

The subject space is a 5'x18' connection between two houses (old and new), built as a result of site-specific grade issues (atop solid ledge), where hydrostatic pressure is moving water and moisture into the 5'x18' area, which is supposed to be 'conditioned space'.

I've had to remove the sub flooring and some framing, and break out a crude trough between the footing and the slab. This does eliminate pooling of standing water on the slab, but I know thatbwetness won't just go away: it needs ventilation and all wood needs to be covered with plastic so as to create a space that doesn't promote mold growth, but allows the trough to dry. A real PITA, but I need to close this up, and moisture-proof/ventilate as well as possible. That is the crux of this post.

Without boring anyone reading this to tears, a little basic background... This is a new construction addition: 500sf footprint, three stories. The addition is built on 10" concrete rebar-reinforced and filled blocks atop a 12"x24" stepped footer that I and two guys built, pinned to the ledge. Said addition sits in the backyard, higher than the original house, and the two and joined together by a a 5' x 18' intermediary structure with its own footing, block foundation, and slab which are tied to the old house's rubble on ledge foundation.

The 5'x18' connection area is the subject, and sits atop ledge, gravel, 2"XPS, and a vapor barrier. Its slab sits below the new addition's footing, by necessity as we could not blast or chip away that much ledge.

The addition, the 5x18 slab, and the 1870s Vic have water that runs from the higher backyard downward to the lower street. The Old house was the only 'problem' before I built this addition. Water went under the foundation, into a drain in the basement, then out to the front yard perhaps into an old cistern.

When I was building the addition, I knew this, and tried to mitigate water penetration under the new structure with interior and exterior perimeter drainage, but the irregularities of the ledge and the straight profile of perforated pipe just doesn't catch all of the water. Some still seeps under the new slab, which (again) has 2" of XPS, and a vapor barrier.

I knew there'd be water coming down. But, was hoping my drainage might do the trick. Nope.

So I've broken a small trough along the edge of the footing and slab to capture the water that gets down though the footing (it does so atop, midway, etc.). I always figured the plastic I put under the slab, as a moisture barrier, might serve to protect the space above if water went underneath. (The footing is pinned to the ledge, and the slab is not holding that footing at all.)

I did not, however, plan for an open ditch between slab and footing for the water to have place to go, so now I need to manage/allow for that 'area' to have a place to 'dry to'.

Or, so I 'think'!

The easy way would be to Zip tape more plastic over the trough connection that to the plastic under the slab, and mechanically affixing same to the block wall. I could possibly fan blow air though that area and skip building a soffit.

A more complex way is to build a waterproof (on the inside) soffit (say, lined with plastic) and then use an exhaust fan and floor or wall register to allow conditioned air into the 'space'.

Anyone have any suggestions? I'm leaning toward the latter, but the former would allow me to have more floor space. I have PT 2x6 joists hung on a ledger 5" above the slab. That's as high as I could go. They sit on the wet footing, with plastic as a capillary break. I was going to treat these boards, and the underside of the subfloor, with Bora-care. I'm not sure if I ought to put XPS at the tops of each joist bay and along the footing, or leave alone. I could always heat from above with Dirta Heat or a radiator. There is 2" of XPS on the exterior block wall, which is only a couple of courses high.

I also know I need to look at mitigating the part of the backyard that is not under the additions roof. This is a big source of water, but another year. I've still got electrical, flooring, paint, tile, cabinets, trim, doors, and more.

A few photos:

1. This'll make more sense in a minute. Shows the foundation footings and blocks, in juxtaposition to the site. Note the slope from above is fairly severe. What you see below the door is to be a finished pantry off the kitchen. I have framed and sub-floored this area, and have removed the subfloor as the plastic barrier idea I had, which was under the joists but above the concrete slab, was not sealed well enough and I knew it.

Grey Wood Composite material Building material Urban area


2. Here's what I'm up against, in terms of my site's slope. There is simply no way to grade away from this stem wall/foundation. I'd go broke trying to chip away that much ledge. The top soil you see is maybe 6"-8" at best. The wall has poured and rolled Karnack all over the thing, XPS, and tried to then put a French drain atop ledge at the point where the footing and ledge merge with J-drain dimple as a catch. Not working well.

Wood Plant Grass Road surface Automotive tire


3. Here's a shot showing the weed mat over the drainage piping before we covered with gravel, 2" XPS, rebar, and plastic barrier.

Road surface Asphalt Composite material Groundcover Gas


4. I tried hard to get help. Had an old timer architect, and a younger one consulting. Everyone is so busy these days no one really had answers. Did my best. (Should have posted this sooner but hard to DIY a house build and type lol.


Rectangle Slope Font Parallel Schematic


5. I've gotten to the point where the envelope is done, roofed, sided, trimmed, insulated, and sheetrocked. Am priming, readying to do my floors. I knew the footing was a problem, and boy what a bummer. Forced me break the slab. Worked immediately to resolve the flooding in this room, but not the other side of that boiler, where the pantry lives.

Gas Composite material Wood Handwriting Concrete


Floor Flooring Gas Asphalt Composite material


6. That I had to remove the subfloor bc I just knew water was under there, even with a plastic sheet over the whole floor, taped up onto the studs, I know this was a moisture pit. I broke the slab as well as I could with a bit of a slope, and tunneled under that plate which is supporting a joist. Also cut out a small plate sitting on top of the footing. I will probably slip plastic behind and under the plates, and reinstall to shore up that framing. Then tie plastic sheet from the mud sill (I have some Tyvek and plastic all around thinking I might need this). Then tack to bottom of joists and terminate into the slab a few incudes in from the trench. Like this I'm keeping the moisture inside the plastic and trough areas, footing area, block area. I then hope I can push or pull some air through either with a fan exhaust or a fan to push air out of a exterior ent pipe. Not sure which is the better of both evils. Ideas anyone?

Wood Font Gas Tints and shades Concrete


Any tips, or comments much-appreciated. I'm working on this today.
 

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retired framer
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I read some of it but got bored reading.
You have a water management problem.
You need a drain to a sump pit and dimple board that will direct the water to a drain below the slab that will take it to the sump pit where it will be pumped out.
 

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I read some of it but got bored reading.
You have a water management problem.
You need a drain to a sump pit and dimple board that will direct the water to a drain below the slab that will take it to the sump pit where it will be pumped out.
Funny, I was going to somewhat post the same.

The reading just doesn't make much sense.

Find a low point, direct water to it and install a good dewatering sump and high water alarm.
 

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Did not read the entire post, skimmed it and looked at the photos.
You have a few options and may need to deploy all of them.

One. Divert any and all rain water that you can capture and redirect from the high area around and away of your structures. This is where my primary focus would be. Even if that means jackhammering for a prolonged period of time, into the rock face, to create adequate run off channels, with or without pipes, ...
Two waterproof all outside concrete and stone surfaces multiple times, then line with a waterproofing membrane and crushed stone around the structure to divert water away.
Then on the inside, you will not be able to have soft materials unless you can keep it dry. You may have to rebuild part of the structure with blocks higher up, so you can waterproof on the outside, and let breathe on the inside by using a drainage mat for basements - as shown by Neal, that will allow moisture to drain down, into a trench.
If you have very severe water issues still, you may need to drill a pit for a sump pump and actively pump water when the weather gets bad.

Looking at the photos, I feel like a mistake was made by nearly building on ground with soft materials and not pouring higher concrete walls, or higher stone work; which can be adequately waterproofed, and by using drainage mats and gravel on the outside help keep water away.
 

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Discussion Starter · #6 ·
I read some of it but got bored reading.
You have a water management problem.
You need a drain to a sump pit and dimple board that will direct the water to a drain below the slab that will take it to the sump pit where it will be pumped out.
Sorry about the long-windedness, and apparent poor writing. I am unable to drain to a sump pump but thank you for stating the standard for most basements. This situation is different.
 

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Discussion Starter · #7 ·
Funny, I was going to somewhat post the same.

The reading just doesn't make much sense.

Find a low point, direct water to it and install a good dewatering sump and high water alarm.
Thanks for confirming my writing is wanting for improvement, and for the second common sense suggestion I have already ruled out due to the site's restrictions. What isn't apparent, from both my writing or the photos, is there are 5-6 schedule 40 pipe sleeves where I dug and aim the trenches. any of those will suffice as an exit path for excess water.

The main reason a simple drain tile won't work is because I would need to hammer out the ledge BELOW the footing, and that would be a structural issue. Tanks for taking time to read my post. I will refrain from making this mistake in the future.
 

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Discussion Starter · #9 ·
Did not read the entire post, skimmed it and looked at the photos.
You have a few options and may need to deploy all of them.

One. Divert any and all rain water that you can capture and redirect from the high area around and away of your structures. This is where my primary focus would be. Even if that means jackhammering for a prolonged period of time, into the rock face, to create adequate run off channels, with or without pipes, ...
In my post I mention that I need to deal with the outside. I dod not go into specifics. Your comments are exactly what I intend to do. I dug out the foundation, so excavating a little topsoil, and figuring out how to divert the water that runs down same is a project for next year, but an important one. Not what I was asking about in my OP however.

Two waterproof all outside concrete and stone surfaces multiple times, then line with a waterproofing membrane and crushed stone around the structure to divert water away.
Per my post the outside concrete block walls have: 1) Karnack coating; 2) dimple mat to move water downward to; 3) drainage pipe in washed stone pitched with clean outs to a low point on the property where same sees daylight.

Then on the inside, you will not be able to have soft materials unless you can keep it dry.
I am aware of this.

You may have to rebuild part of the structure with blocks higher up, so you can waterproof on the outside, and let breathe on the inside by using a drainage mat for basements - as shown by Neal, that will allow moisture to drain down, into a trench.
If you have very severe water issues still, you may need to drill a pit for a sump pump and actively pump water when the weather gets bad.
BTW: Like your name 'ice rabbit'. I am not going to rebuild the structure as it is unnecessary, but thank you for your good suggestions just the same.

Looking at the photos, I feel like a mistake was made by nearly building on ground with soft materials and not pouring higher concrete walls, or higher stone work; which can be adequately waterproofed, and by using drainage mats and gravel on the outside help keep water away.
The scope of the post was intended to focus on getting airflow into a space that will always have a little moisture, but not be a river. Mitigating the water is something I am working on. The budget I have would not allow me to dig/break the ledge. Everyone in my area has the same problem. We figure out ways to succeed. I will have any water which cannot go under and out diverted away. I am just looking to figure out a means of encapsulating the trough in a way that keeps the moisture off of the hood, and allows airflow for a means of drying. Thanks again.
 

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Discussion Starter · #10 ·
Explain why it is different. You have water coming in above the floor with no where to go?
View attachment 712571
Incorrect. I have a place for the water to 'go'. But, there is residual moisture that I want to keep away from joists and subfloor. Your illustration is a normal foundation footing which is at or below the slab. Not my situation at all. My footing is as high as two feet above the slab. The trough I have, and the drainage solution I have in place, removes the bulk of the water. This is not what I was looking for in my OP but again my post is apparently such that it is hard to discern that point. Sorry.
 

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Incorrect. I have a place for the water to 'go'. But, there is residual moisture that I want to keep away from joists and subfloor. Your illustration is a normal foundation footing which is at or below the slab. Not my situation at all. My footing is as high as two feet above the slab. The trough I have, and the drainage solution I have in place, removes the bulk of the water. This is not what I was looking for in my OP but again my post is apparently such that it is hard to discern that point. Sorry.
Sorry I was answering to the wrong thread. Opps.
 

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Well, as far as breathable wall on the inside of the wet room.

PT lumber may be required. Need to have a foam barrier between concrete or block and the lumber, to avoid moisture wicking.
Insulation ... mmm ... has to be breathable. Foam is out, just traps moisture and prevents breathing / drying out. Probably would neet to stay 6-12-24" off the ground / wet area with insulation.
Wall finish. Drywall is out. Cement board with tile + grout. If it works for showers, saunas, bathrooms, ... should be good, and easy to clean/dry. Stucco or stucco like panel board also could work. Quick and easy.
Drying. Create air flow. A window or two that you can leave partially open, or some strategic vent openings ... outdoor ceiling fan ...
 

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Incorrect. I have a place for the water to 'go'. But, there is residual moisture that I want to keep away from joists and subfloor. Your illustration is a normal foundation footing which is at or below the slab. Not my situation at all. My footing is as high as two feet above the slab. The trough I have, and the drainage solution I have in place, removes the bulk of the water. This is not what I was looking for in my OP but again my post is apparently such that it is hard to discern that point. Sorry.
Still then not sure of your questions.

Sounds to me that you want to get rid of moisture not water. You will handle the water because it's to complicated to explain....just moisture.

You will need a fan, sized correctly and hooked to a humidistat.
You will also need a louvered opening across the space to bring in outside air....

I'm sure maybe you already knew that so if that's true what's your main question.

Also, and I may look dumb here, what is the ledge you speak of?

Are you building on rock?
 

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Discussion Starter · #14 ·
Still then not sure of your questions.
Just one, but I did drift into other topics, which is probably why I was called out for y poor writing.

Sounds to me that you want to get rid of moisture not water. You will handle the water because it's to complicated to explain....just moisture.
Yessir. I am probably going to treat this wet area like a shower pan situation only not with as robust materials, and yes a fan.

You will need a fan, sized correctly and hooked to a humidistat.
You will also need a louvered opening across the space to bring in outside air....
I have several fans, registers, etc. Conditioning a space is common so yes I've contemplated this way if handling the moisture.

I'm sure maybe you already knew that so if that's true what's your main question.
I was just wanting to converse with others who have dealt with similar circumstances to learn what I can and share ideas,

Also, and I may look dumb here, what is the ledge you speak of? Are you building on rock?
Solid granite. Where I live it is the hardest there is anywhere. People, neighbors, have gone broke trying to break this rock. I opted to use it as a foundation as there is nothing stronger. But... there are obstacles and problems as a result. Thanks for reading and responding.
 

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Discussion Starter · #15 ·
Plant Building Window Tree House


Ice Rabbit: The above shows the two houses. I have built the back house from ground up with two masons, two framers, and a roofer. I understand basement waterproofing techniques as the front house has water going under it for 150 years. My question was more: should I build a soffit wind tunnel and Kerdi the **** out of it, or do something less aggressive, e.g., some x-mil plastic vapor barrier taped to the stuff I already have, and fixed to the slab with silicone and some Azek strips and Tapcons, or Ramsets. I didn't mean to confuse or ask for basics on how to do drain tile in a basement, so sorry guys really.

Well, as far as breathable wall on the inside of the wet room.
Believe it or not every shower is just that. I am looking to do this inside out. Am debating whether or not it is worth losing precious interior space by framing out a soffit, or using heavy mil plastic mechanically fixed to wall and floor and a fan or exhaust. I have several right here in my living room lol.

PT lumber may be required. Need to have a foam barrier between concrete or block and the lumber, to avoid moisture wicking.
Insulation ... mmm ... has to be breathable. Foam is out, just traps moisture and prevents breathing / drying out. [/QUOTE]

Everything in there is PT. I actually have a Bora-Care kit I snagged for $160 that is supposed able to ward off mold for eons. I'm debating using this on the joists, then coating same with primer or even wrapping them. Called their tech support 3x today no avail. I think they were busy.

Probably would neet to stay 6-12-24" off the ground / wet area with insulation.
I can cobble in 2" XPS between the joists at the top under the subfloor. I can also nail same into the block and footing. It's negligible. I had no insulation over this exact same space, had a subfloor, tile, and sleepers (PT) on grade. I let the water go under and never had an issue. I posted this because I wanted to see what others have done.

Wall finish. Drywall is out. Cement board with tile + grout. If it works for showers, saunas, bathrooms, ... should be good, and easy to clean/dry. Stucco or stucco like panel board also could work. Quick and easy.
It's not that wet with the trough. I am basically directing water under and around the slab. I just need to blow fresh air on the open cavity so it can dry.

Drying. Create air flow. A window or two that you can leave partially open, or some strategic vent openings ... outdoor ceiling fan ...
There is a big window in the room, but the 'action' where the moisture lives will be under the subfloor. So, the window is not a player.
 

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Brain storming. ( I will have to re-read the thread and a couple tangents )
What if ... it were essentially a wet tunnel / bridge type thing, with the flooring a bit higher off the ground, with strategic panels you can lift up for inspection - not unlike living quarters on a boat and the engine bay below - but you create a separation between the wet & humid below and the dry higher up. You could create something low with sealed walls, then serious plastic on the bottom of the joists, taped and sealed, outer vent holes and forced van ventilation when needed like to deal with crawl spaces and basements.
 

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All the fun.... while trying to build on top of a big rock.

Not sure that applies to the "do it yourself" chatroom.

Be interesting to see if anyone pipes up about building that way and at the same time has the same water issues you have.

Good luck with your build and I'll be lurking.
 

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Discussion Starter · #20 ·
Brain storming. ( I will have to re-read the thread and a couple tangents )
What if ... it were essentially a wet tunnel / bridge type thing, with the flooring a bit higher off the ground, with strategic panels you can lift up for inspection - not unlike living quarters on a boat and the engine bay below - but you create a separation between the wet & humid below and the dry higher up. You could create something low with sealed walls, then serious plastic on the bottom of the joists, taped and sealed, outer vent holes and forced van ventilation when needed like to deal with crawl spaces and basements.
My first attempt had plastic under the joists up the footing and to the sill plate. The whole slab was isolated, or so I thought. But when we framed the floor, and were just in there moving in tight quarters, some of that plastic must've gotten punctured, as the puddled water beneath got through. So, there was water under and above.

I suspected this as I really thrash around a lot when I'm working—a product of age and not loving the 'process' so am always rushing—but it wasn't until I finally got to the task of trying to figure out how to push air down there (always my plan), and removed a panel put in just as you've mentioned above for inspection purposes, and also to run a duct pipe of some kind, that I caught a very slight whiff... of... mildew.

The subfloor is Weyerhauser's best Gold product purpose-made for wet-dry cycles too. It's gone to the dump now.

As I shop vac'd the water, I decided to flip the hose and pump air under the plastic to get an idea if such a plan might work. Here's the 'bubble' or 'tunnel' effect I saw...

Automotive tire Wood Motor vehicle Automotive exterior Tread


Wood Gas Tints and shades Rectangle Metal


So, it's raining today, and I will watch the water to see if the channels I've made in the edges of the slab catch and direct the water to the drain I have made out of an unused under slap pipe sleeve. I know I can pump air with a barrier, but noise, and how are considerations.

I considered making a stem wall out of cut concrete blocks, just to the dry side of the channel, atop a capillary break, another break on that, a plate, then joists and rim. Frame a soffit, and waterproof the thing so the exterior block wall, the footing, and the moist channel would be isolated completely. Then use a standard exhaust fan to the outside, with a register on the opposite end, to 'condition' that space. Sounds like a lit of work, where I may be able to do a better job with the plastic barrier, using more care, and a couple of layers, and allowing air to pass through that.

I'll always have access to this area. Scraping the top soil, and hammering channels will help, but where the wall and ledge meet is a valley. Snow in winter just piles up there. I used to shovel it out each snow.
 
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