French Drains and Home Foundations

Tree roots may cause blockage. A sump pump is a very well excepted addition. Grading soil away and downspout use is the place to start, a sump pump is always recommended.

We have a lot of them in my neighborhood (10 feet above sea level). They are simple and effective as near as I can tell.

Above you home try and get a small valley created to guide water from the mountain away from you home. Gutter drains must go at least 10 ft away from the houses to be effective.

A sump pump wont help water leaking in a mortar joint in the wall it will stop water from coing up threw the floor. If you know were the french drain empties to that would be were i started to look for possible trouble. Next time it rains see if you have a good flow of water out it. If no water or not much water then you may have a plug.

Oh yeah I forgot on the French Drains they will get clogged and need to be redug but also the drain level can change to draining away from the house to pushing water towards to home if they are really old. I saw this in Fla, and La. where they had actually shifts drain angles because of the silt that had gathered over time.

I am preparing to build another home, and it is something that I am working very hard to make sure I have no foundation leaks, as the wife wants a partial basement. I am using the roof overhang, soil mounds, and finally French drains that slope to a sump pump-just in case.

I think I will have enough protection from the preventive measures, but the pump will be my fail-safe method to prevent water intrusion. I certainly think it is possible for a French drain to become clogged-from soil if nothing else.

Best Regards,

Ing. Robert Forbus

Oh sure - do the job right - where's the challenge in that?

you made me laugh first time in a week thank you!

...better to solve the cause of the problem rather than relying on a sump [and]pump, which simply deals with the symptom. French [tile-type foundation or footing/mud sill] drains do [can] clog over time — but 10 - 20 years seems typical — and I think that modern drainage fabric helps.

Ken, well spoken but I sense it could be an oversimplification. We should first start with a truism, namely: that virtually any drainage or water-intrusion prevention "system" can be overwhelmed given the right (or would that be wrong) circumstances and conditions. Accordingly it is equally correct (just as valid) to see an interior sump, not as superfluous (viz., not as symptom related only), but as a reasonable (i.e., a backup) redundancy. Hence, it is not at all uncommon for new houses to be constructed, both, with exterior perimeter tiling/drain piping (what is incorrectly being called French drainage) and with interior, embedded or open (i.e., true French) drainage leading to a (usually interior) below-subfloor-level sump . . . from which drainage to exterior can be effectuated (where possible) by gravity or with immersible pump. (Such a sump can also serve well in the event of "plumbing accidents" unrelated to outside precipitation . . . or during rare flood events!)

Additionally, with original post-er's situation there could be an additional (until now overlooked) dimension which, for him, might make the installation of interior drainage to sump a more workable (even if only temporary) solution. For example, weather conditions might preclude excavation until a later date . . . but present water intrusion conditions are "unwilling to wait."

To help make this clearer and add perspective, a description of "tile" drainage is offered: http://cr4.globalspec.com/comment/250087/Re-Exterior-Tile-Drains-and-Home-Foundations

Indeed, drainage fabrics (including socks) are a useful and convenient augmentation to retard some (but not all) soil particle intrusion; but care must be taken in the manner of backfill and choice of fabrics, depending upon soil types. It was said that perimeter sub grade drains have an (ostensibly rather limited) "typical" life expectancy. This may may or may not be true in all cases . . . and one must take into account that, with socks or landscape cloth (improperly applied), an apparent drainage failure could, in fact, be caused by the "filtration" (the landscape cloth) as its "pores" become clogged.

(With these additions and provisos. . . your comment is able to stand as rated and without demotion.)

There are many options to your query - French drains work to an extent - So do adding drain tile around your foundation - directed into drain holes filled with material from 1/2" to 2" assorted - you need to look at the volume of water your grounds are dealing with - inches of rain versus sq yards of ground that needs to be saturated - it can add up to a lot of water - thousands of gallons in a few short hours of deluge... also, you need to know where your water table resides - at what level compared to your house. This wil tell you if a French Drain or Weeping tile are the answer... Also you need to look at the sq footage of your roof runoff and add about 20% to 30% of that figure to get the volume of water(dependent on the slope of the roof and the over hang of your rafters.).

It sounds complicated, but it's not really - land saturation affects all home owners in one form or another - sooner or later - you just need to get the calculations right - I can be reached at norfolk@telus.net.

Cheers

Hydraulic cement

Hydraulic vs. non-hydraulic cement

Hydraulic cements are materials that set and harden after being combined with water, as a result of chemical reactions with the mixing water, and that, after hardening, retain strength and stability even under water. The key requirement for this strength and stability is that the hydrates formed on immediate reaction with water be essentially insoluble in water. Most construction cements today are hydraulic, and most of these are based on Portland cement, which is made primarily from limestone, certain clay minerals, and gypsum in a high temperature process that drives off carbon dioxide and chemically combines the primary ingredients into new compounds. Non-hydraulic cements include such materials as (non-hydraulic) lime and gypsum plasters, which must be kept dry in order to gain strength, and oxychloride cements, which have liquid components. Lime mortars, for example, "set" only by drying out, and gain strength only very slowly by absorption of carbon dioxide from the atmosphere to re-form calcium carbonate through carbonatation.

Setting and hardening of hydraulic cements is caused by the formation of water-containing compounds, which form as a result of reactions between cement components and water. The reaction and the reaction products are referred to as hydration and hydrates or hydrate phases, respectively. As a result of the immediate start of the reactions, a stiffening can be observed which is initially slight but which increases with time. The point at which the stiffening reaches a certain level is referred to as the start of setting. Further consolidation is called setting, after which the phase of hardening begins. The compressive strength of the material then grows steadily, over a period that ranges from a few days in the case of "ultra-rapid-hardening" cements to several years in the case of ordinary cements.

Think of your house as a raft sitting on the surface. As soon as you dig a basement under the house, it acts as a displacement hulled boat. Every boat has a bilge pump; every basement should have a sump pump. 'nuff said.

Your home built in the 70s should have the usual well built surround drainage system with plastic drainage pipe etc. I suspect that , as you have stated , your house is situated in a low area where water is bound to accumulate .

First ; What do french drains have to do with your immediate problem ? A french drain is used to drain water away from a sway in the land around and far from a home ?

Second ; If your house is located at the base of a hill and subject to springs and heavy runoff , i cant imagine that you dont have a fuctioning sump pump now!

If your only problem is a leaking mortor joint right now , i would suggest you get religious like now and thank the big guy for saving your ass !

Wondered if anyone on forum has experience with home foundation drainage particularly french tile drain systems. (Note that french drains are surface drains . . . such as on the inside of the basement . . . often leading to sump and immersible sump pump.)

With house situated on a hillside, and diggable soil, you could consider a curtain drain uphill from the house.

If you end up excavating and renewing your foundation tile drains . . . recommend using solid, ABS perforated (in stead of tiles, or corrugated flex) and adding solid clean-out lines to the surface. If this had been done originally, your foundation drains would most likely still be functioning well.

hello guest at post number 14.

i agree with everything you recommend. seems counter-intuitive sometime, but always be sure the curtain drain is above what you want drained, if the water is coming from that direction. yes the black corrigated stuff clogs up in a couple of years. yes, the 6" drain is best. i have used 4" successfully also. that would be the white abs with holes in it. remember to put unperforated curve down. in really heavy flows under a house, i have had to build concrete dams across, backed with plastic on the wet side, then gravel, pipe, gravel. it all has to slope in the direction you want it to go. it is a lot of hard work, but is very effective. the last one i did had an output flow rate of about 30 gallons per hour. this was from only 20 feet of perforated pipe.

. . . seems we're on the same page; but, please, a couple of clarifications . . .

1^st

You mentioned: "...that would be the white abs with holes in it."

Could it be lightweight Coex (drain and/or solid) pipe you are referring to? Coex (which is white) does provide an inexpensive and easier-handling/easier-working alternative to (black) ABS, but I would be leery of using it below relatively shallow depths (below 1 - 4 feet sub grade . . . such as at foundation footing/floor level . . . where the heavy duty strength of ABS will give "permanent" assurance against collapse/deformation/disjointing . . . and be more suitable for auguring if cleanout capability is desired).

2^nd

If I interpreted correctly, I understand your statement, "...remember to put un-perforated curve down," to mean: lay down solid (or corrugated) drain pipes such that the holes (or perforations) on either side of the pipe's bilateral center-plane face upward/skyward. While this might seem intuitive (at first), closer examination reveals numerous reasons why drain piping should be situated with holes oriented downward:

• Holes upward promote the gravity-assisted (alluvial) washing of soil into the pipe where it can accumulate and thereby reduce/impede flow . . . even to the point of backups due to clogging or damming. . . &or to a point where pipe's carrying capacity is more readily overwhelmed by water entering the pipe . . . as a result of which . . . increase likelihood of basement water intrusion during heavy precip/runoff events.
• Holes downward, on the other hand, serve to minimize soil entry for several reasons.
• The holes are not in the path of water (and soil) washing downward over the pipe.
• Gravity serves to exclude rather than permit soil particle entry into the piping.
• Due to the natural soil illuviation, whereby soil particles become more compacted and cemented—and therefore less susceptible to transport—with increasing subsurface depth, less soil is available to enter pipe than with holes placed upward.
• With holes upward, only a limited range (in fact only two narrow ranges) of soil directly above a pipe's holes is drained . . . leaving soil (fully or partially) un-drained:
• In space between holes,
• Directly above pipe centerline,
• Outward towards the house-perimeter terrain, and most critically,
• Inward towards the foundation wall as well as downward of the pipe holes (in all directions!
• Because (properly installed) drain piping relies on pressure in addition to simple gravity-induced flow—yes, this is a functional aspect which is commonly overlooked—placing holes upward, in effect, disables pressure induction leaving only gravity flow to remove water . . . and that only from the soil overburden above the piping.

In short, it is a superficial intuition as to how (but not as to how not that) drain piping is designed to function that so often underlies the (mistaken) sense that holes/perforations should be placed facing upward:

• Drain piping (and old-style tiling) is not designed to function by capturing "falling" water as it permeates downward through the soil. Moreover, the spacing of holes would leave most such water un-captured
• Drain piping (and old-style tiling) does function by lowering (and levelling) the local, proximate water table (i.e., the full-saturation horizon surrounding the building) below (or to the bottommost level practicably attainable adjacent to) a building's foundation walls (or footings).
• The idea is to capture and transport away (not falling, but) rising water during precip events during which downward-permeating water would otherwise (in the absence of drainage tiling) raise the local water table to a point at which large portions of foundation wall would be exposed to saturation . . . and penetration at vulnerable points.
• When holes are erroneously placed upward, then that portion of the pipe-midline plane below its holes (and continuing into underlying soil) becomes a vertically and horizontally defined volume that will not be drained at all . . .
• In effect, one will have raised the local water table when the aim is to lower it . . . so that water which could have been removed (with holes downward) can now intrude upon the foundation floor &or walls.
• Moreover (again, due to hole spacing), even if the water table rises to hole-level at top of pipe, a substantial portion of water will not be drained but will spread outward, including towards the foundation wall. But that's not all . . .
• Saturation at (elevated) water table, once "achieved," by increasing soil flux will actually facilitate soil particle transport towards the pipe holes . . . thereby exacerbating the intra-pipe soil intrusion effects mentioned above.

So there it is: keep holes down for drain pipes to function as designed. I could have given more explanation/examples but . . . getting too long already. Any questions . . . will try to explain further.