What product(s) do you recommend for sealing and/or painting a basement floor that has some hydrostatic pressure at times. 10-15% moisture during heavy rains. The basement usage is for storage and a woodworking shop. The air level relative humidity is kept below 75%. I have come across a few waterproofing products but are all labeled not for floors
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The only thing that's going to work reliably for any time is a perimeter drain.
Just what ya wanted to hear, right?
SamT
Agree. Seal it good enough and the concrete will heave and crack.
With water, you can't stop it, you can just guide it!
If it's a matter of wanting to put a finish floor over it, think about either Delta FL which is a sort of plastic underlayment that vents beneath it with flooring over that, or one of those new "systems" that have the plastic "bumps" under them and T&G subfloor on the top, sort of like tiles.
That'lll keep the dampness out from under the finish floor.
Steve
Confused yet? Lemme explain it again.......
I forgot sealing the concrete with underlying moisture will cause it to heave and crack.
The basement does have some form of a french drain. I don't know how to tell if it is completely around the inside perimeter. There is a sump pump. It only runs during the heavy storms. Which is also when the moisture level in the floor is at the highest.
No Bull,
>>The basement does have some form of a french drain. I don't know how to tell if it is completely around the inside perimeter. There is a sump pump. It only runs during the heavy storms. Which is also when the moisture level in the floor is at the highest.
Indicative of a poorly designed/implemented system.
Probably only on inside of perimeter.
It may, might, possibly, there's a chance it will, help to cut a kerf all the way around the slab next to exterior walls. Cheap and DIY. Cut all the way thru. Caulk top of kerf with appropriate material.
SamT
It only leaks when it rains, right? LOLThe perimeter drain needs to be on the outside of the footing to catch water BEFORE it gets in.BTW, 75% RH inside is way too wet anytime of year. A house should be less than 40% to prevent issues with mold, condensation, etc. Until you get things right, a dehumidifier can help.
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I have been using a couple dehumidifiers. They are being emptied twice a day. The humidity is 15-35% in the winter heating season. The central air conditioning is reducing the humidity level in the house an average of 10%-15% below the outside air relative humidity. I thought a ten percent decrease was about average. I guess it is time to look at the AC dehumidifier. The house (upstairs) does not feel humid and I hear the pump from the AC condensation running 2-3 times per hour. It has a half gallon reservoir. Although I know my humidity meter is not the best, I also know that there should not be condensation on the AC supply duct. There was even condensation dripping from the duct about 10 feet away from the AC A-frame. This looks like I may have surpassed my DIY skills. Time to call an HVAC expert?
Is the AC duct insulated?. Should be.
Just to see how much of affect it would have, I installed 1/2" Styrofoam on 3 sides of the first 10' of duct nearest the A-frame. This has helped but when the humidity is high you can see a few drips of water from around the seams. I'm hoping that increasing insulation by 2x - 4x the increased thickness will eliminate that condensation.
New question: How do I get the AC to remove more moisture from the air.?
The system has 5 outlets in the basement. I have been keeping the vents closed about 80%, trying to prevent the basement from being more than 10 degrees colder than the rest of the house. There is only one inlet in the basement. It is within 6 feet of the A-frame, near the ceiling
(I brought a new humidity meter that shows the humidity is not as bad as I thought. It reads 45-50% in the house and the basement, while the outside RH is 90%)
The duct should be sealed before it is insulated; the whole perimeter of the duct. Any leakage in the duct is a probable cause of excessive moister. Luck.
Thanks -- What is the recommendation for the top of the duct, which is installed next to the floor above?
You are not going to like my response, but the duct should be sealed all the way around its periphery then insulation added, any leakage in the duct can cause a moister problem. The best that I can do. Lots of luck.
paul... i put a french drain on the outside of our first house.. never will do that again.. unless forced to by the Architect
we overdig all of our holes.. then put in 12" of 3/4" crushed stone..
with a perimeter 4 " pipe system around the inside of the foundation leading either to daylight or to a sump..
the pipes also have risers so they can double as Radon mitigation pipes if radon is detected..
you remember the pitch of our lot ? ... well that foundation drains to daylight..
12" crushed stone, 2" foamular (pink ) , 6mil vapor barrier, 4" slab...
bone dry basementMike Smith Rhode Island : Design / Build / Repair / Restore
Read your post regarding french drains, what if running drainage to daylight is not a possibility? Do you rely on sump to pump to surface and have swale carry water away from house? My lot is level and looking to put drainage tile at my footings and away to a french drain, had considered punching in to connect to sump pump but leary of cutting at footing on this old building so had hoped a french drain could handle to load...
yes... if i can't drain to daylight ( on one job we had to go more than 200' to get the pitch )
then we will lead our pipe system to a sump and pump it out to a drainage solution..
in one job we had to build a drywell pipe system to take the pumped water..
that system pumped for about 3 months a yearMike Smith Rhode Island : Design / Build / Repair / Restore
Same here. French drains are for the French.
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From:
Piffin <!----> View Image<!---->
Aug-19 8:09 pm
To:
MikeSmith <!---->
Same here. French drains are for the French.
Uh, oh....
Before I decide whether or not I want to mix it up with you two, I better find out if we mean the same thing by the term 'French Drain'....
Perf'ed pipe--either rigid or accordeon--laid on a bed of ¾-net gravel at footing level on the outside perimeter of the foundation, with a T at the low corner and a non-perf'ed pipe connected there leading to daylight or other acceptable drainway. Said perfed pipe covered with an additional 12-18 inches of ¾-net, a layer of geotextile, straw, or builder's paper, then backfill with coarse sand up to 6" below grade, lay on a membrane flashing sloped away from the foundation wall, then add topsoil and landscape over all....
Is that it?
Or do you mean an exterior perimeter drain built the same way but connected to a dedicated weeping field instead of running to a drainway?
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
it matters not whichever..
the problem i have with perimeter drains outside the foundation is this.. they are designed to intercept runoff as it percs down thru the soil against the foundation..
they do nothing for a rising water table.
since our springtimes are all rising water tables the water rises faster in the middle of a typical foundation than it can flow to the ouside..
also most footings intercept this flow... so the water in the middle of the foundation can't even get to the drain system..
i could care less about the outside of my footing and the outside of my wall..
i want the inside to be dry .. so that's where i put my drain systemMike Smith Rhode Island : Design / Build / Repair / Restore
The general expectation around here is that basements are gonna be wet. Most footings are pretty much sitting either right on the Canadian Shield (bedrock) or so close to it as not to matter (like a matter of fractions of a foot). And as we all know, the water flows on top of the rock. A huge percentage of the foundations in this area need to have steps built into them as they follow the rock downhill. I consider myself lucky if there are only one or two steps needed.
My approach to this problem has always been based on the old rule that you can't stop the water, but you can persuade it to go someplace it won't bother you if you think like a fluid.
That being given, I know I'm gonna get ground water and/or percolated surface run-off flowing downhill under/over the footings and getting into the sub-slab area. So I do three things.
1. I encourage water on the uphill side of the foundation to take the easy path (i.e.: the perfed 'French Drain' pipe) and go around the foundation. I do this by making it easy for the water to get into the pipe (lotsa gravel, sand, and other highly-permeable fill).
2. I discourage the water from fighting its way under the footings or through the keyed joint between footing and wall by 'caulking' the keyway joint with bituminous pitch before I tar the foundation wall (3 coats). If the footing is sitting on clean bedrock, I blow it clear of debris and caulk that joint, too. I know this won't stop all the water, but I lay the perfed pipe lower than the footing joint if at all possible, again in an attempt to get the water to take the easy way downhill.
3. What water does get in under the slab I provide easy flow-through conditions by loading up with lotsa gravel--I frequently use 12" or more--and I also make sure it has no trouble running downhill out from under the slab...by installing thru-footing drains of at least 4"-dia. every 15' along the downhill side of the foundation. And then I give that exiting water a final easy ride out away from the house via the perfed pipe it will find there...so the water won't back up against the downhill face of the trench, which is of course less permeable than the drainage materials we used in backfilling.
The places we have seen the most problems keeping basements dry are where the profile of the bedrock forms a subterranean 'swimming pool' with no natural fall-away from the area the house is sited. Lots of guys dynamite the bejasus outta these sites trying to create a run-off path underground...but it rarely works and is expensive as hell. A great number of these places wind up relying on interior perimeter drains and sumps with active pumping systems to lift the collected ground water outta there. Expensive and subject to flooding due to simple mechanical failure or power outages. Workable, but far from ideal, in other words.
My theory on how to deal with these sites is different, but based on the same hypothesis as above. All I do is dump enough gravel under the slab so that it's held above the highest reasonably predictable level of ground water. It does seem a waste of effort and material to install perimeter drainage--whether interior or exterior--in these cases, unless one plans on the active drainage system mentioned above. In other words, I propose just plain floating the entire house above high water on a bed of rock and gravel. So there's water down there. It's not bothering anybody there....
Of course this requires raising the entire building relative to the absolute level of the bedrock. But so what? Final grade is an adjustable level, and height-above-grade is a relative quantity. Pouring a taller foundation wall (if necessary) and dumping 30 to 50 18-wheelers full of permeable fill around it to bring the grade up to the desired level is cheap compared with dynamiting sufficient bedrock to create an artificial subterranean slope on which to set your footings. And it's a permanent, non-mechanical solution, independent of any influence except for 100- or 200-year flood levels which would rise above the slab. If that possibility bothers the HO, maybe he should consider building somewhere else, like on top of a mountain....
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
Thanks Dinosaur,
You gave an excellent description of how to avoid a wet basement when constructing a building. Along those lines, it looks like my best recourse will be to redirect some more of the water away from the perimeter of the foundation. I suspect that under heavy rain conditions (the only time the sump pump has to run) some water is getting under the foundation. Since I can't raise the house, I'll divert some more of the water away from the house.
The salient point is to make sure any water that does get under the slab has an easy way out again. If not, it will rise inside the perimeter of your foundation and that's not what you want happening.
It is possible to retro-fit thru-footing or under-footing drains; if you're going to dig down to the footings on the outside to divert more water away from the house, as you say, you'll be in an excellent position to do that. (Just make sure you put those drains on the downhill side, LOL!)
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
Downhill side? You mean the side where the water is coming down the hill towards my house?
No, I mean the OTHER side...where the water going downhill will run away from the house. But remember, it's the UNDERGROUND SLOPE that's important. If you have a slope on the rock under the house that runs downhill in a northerly direction, you want those footing drains in the footings on the north side of the foundation. Because the water down at footing level will be running south to north no matter what it's doing up on the surface.
I talk about bedrock because that's what we have here mostly. But it's the same for any non-permeable stratum. You hope like heck it's sloped underground to help drain water away somewhere. If it's not, you have to go to method B....
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
Sounds like we all do pretty much the same except for terminology. With the underground rock strata here guiding water flow underground, I can't see any water rising in the middle of a slab like mike gets, when the perimeter drain is there to catch it before it comes in, IF we get a full cellar. but when the ledge outcrops in half the basement, then we get water flowing through and have to guide it back out again.
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You and Mike both being in tidal areas, I would suspect your groundwater levels are somewhat affected by springs and neaps as well as by percolation from surface runoff and snowmelt.
We're far from any tidewaters up here, but the spring melt can dump an amazing amount of water into the ground. In my old place--before I rebuilt it in 95--there was a so-called 'drain' out of the crawlspace that was nothing but a 4" sched. 40 PVC pipe running to the middle of the backyard from just under the access door. That pipe froze solid every winter, being about 6 inches under the surface. As a result, I would routinely see 2½ feet of water accumulate inside that crawl space in the spring.
The floor of the new basement I put under this place is 3 feet lower than the old crawl space (and 20 feet closer to the lake, too)--and I've never had a drop of water come inside. It just flows under and around and goes happily on downhill into the lake not bothering anybody on its way....
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
no springs or neaps... some ground water flow over bedrock..
but most of the problems occur from the rising water table during the wet seasonMike Smith Rhode Island : Design / Build / Repair / Restore
So your basic problem is that the floor slabs are 'below the waterline' for part of the year on a regular basis. That would explain why you don't get much bang for the buck with an exterior perimeter drain.
But why aren't the slabs built above the high-water-table level? Is that level so high that this would eliminate basements in any practical sense?
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
do you mean , " Why is the sky blue ? "
yes..... if you want a basement, the slab will be below the spring time water table in a large part of the island
it's been this way since 1647...it only becomes a problem for those who don't take it into accountMike Smith Rhode Island : Design / Build / Repair / Restore
Ditto
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The sky is blue at your place???
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Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
Hi Mike,
You make a good point with "why aren't the slabs built above the high-water-table level?" How is the homeowner of a 50+ year old tract house suppose to know what the soil/rock is like under the house except an inspection during the high water season. I live Delaware, a few hundred feet above the mighty Delaware river. I used to laugh at the good ole southern boys when they said "every thing is ok as long as the creek don't rise". I too have now become a creek watcher. My basement sump pump only runs after the creek rises.
Joe
our bedrock is well above spring tides, except in two or three houses.
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around here, a french drain is what is employed whjen things fail, instead of doing it right at footing level. They just dig 18" or so, try to create a swale leading to a trench full of 3/4"stone, and sometimes use perff pipe. All it catches is surface runoff, not groundwater, but it is cheaper than going deep so it happens. It is far too popular for the little good that it does.
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