Replies

1. 
   roger_helton | Feb 23, 2002 05:41am | #1

   *
   Jeff, I just finished pouring the footers in my house today. I dont have an answer but it seems like no one else does either. My self dont understand the logic behind putting a perforated pipe around your footings unless they are all within 1ft or so of ground level and the ground is sloped toward the walls. Why would you need these perforated pipes around the footers if no water is coming down the foundation walls to puddle their in the first place. JMHO, Roger

1. 
   Mike_Smith | Feb 23, 2002 06:58am | #2

   *jeff. you did right.. the footing drain either has to run to daylight or to a sump.. if it doesn't go anyplace.. it does no good

1. 
   Tripper | Feb 24, 2002 05:36pm | #3

   *Roger,footing drains also protect the footings from ground water, not just suface water. You were right that no one has an answer(including me). Foundation drainage is by far the most inconsistant, overlooked and unregulated aspect of home building. For every ten builders I've found waterproofing one way, I find ten more doing it completely opposite.(disregarding different soil conditions). I wish there were a general standard like there is for all other aspects of homebuilding. Most builders I know don't do diddly because they are all 30 years old and most basement problems begin after many years.(No call backs in 5 years, must be doing it right). I guess I'll rely on my five years of hydraulics experience and ten years of building to figure out the best system.Thanks for replying.Jeff

1. 
   Mike_Smith | Feb 24, 2002 06:25pm | #4

   *tripper.. 1st.. we use a poured concrete foundation.. and we snap ALL our ties in and out.. we seal all the tie holes with plastic roof cement and give the foundation two coats of asphalt based sealer.. but... we're not building a boat... we have poorly drained soil.. so i always pour our fondtions on 12" of 3/4" crushed stone.. with an internal 4" drain system under the slab either drained to daylight or to a sump.. .. i think most waterPROOFING systems will be penetrated unless there is a path or less resistance for the water to follow... also... a lot of problems are caused by high seasonal or unusual watertables, which no waterproofing system is going to take care of...we always have dry basements... at least every one since 1975....

1. 
   Schelling_McKinley | Feb 25, 2002 07:41am | #5

   *We have dry basements except in two cases. The first was a flat lot where we put in a foundation drain that went to a dry well. We also had a sump that drained the stone under the basement slab. The water table rose and overwhelmed the capacity of the sump pump. We were able to lower the water table in the spring by adding a second sump which completely solved the problem. Our second was on a sloped site with a drain to daylight. There was also a small piece of bedrock which raised the building 6" so that we could cover it with stone under the slab. We noticed a wet spot in the basement carpet near the end of the job. We peeled it up to find a small wet crack in the slab. We drilled a hole in another area to put in a sump and water spurted up like a geyser. There was only a tiny dribbling of water out the daylight drain and yet somehow water pressure had built up under the slab. Our only explanation was that a vein of water was coming up through cracks in the bedrock to exert this pressure since there was obviously no water around the outside of the house. The sump cleared up the problem after running for a total of one hour. It is hard to argue with water.

2. 
   Tim_Mooney | Feb 25, 2002 06:09pm | #6

   *This is a good post. My father built many in the ground as the one I live in which is the last he built. He played with this question as long as I remember.He used to say as it was said above that no waterproofing system would hold the water. He felt like water was too strong. He thought that to accept its presence was a better idea.Thus divert it, not try to hold it out with wp.He succeeded for as some one said over five years. Actually where he failed was not putting crushed stone under the slab and the footing. He always used pumps with or with out daylight presentations. He always ran to daylight when he could.Now that he is gone and I have worked on his problems, I think that crushed stone under the whole ball of wax would relieve pressure in any flood circumstance. That is only my thoughts as it is not backed up anywhere I know; but it is a saftey feature of diverting water and not holding it. Thanks for the post as it is one I needed to hear you guys speak. Now you can jump on this and prove me wrong or right. I would like to know the best answer also.

3. 
   Mercer | Feb 25, 2002 07:18pm | #7

   *Your scenario is exactly like mine. My lot is flat and except for a tiny bit of dirt for top soil it is all sand. Building code here requires that you put in a perimeter drain tile and run it to a sump or to a rock pit ( which has to be engineered). My problem with it is that sand is a excellent drainage material so why would I need a perimeter drain. Our climate is semi desert. It might make a difference if you saw rain 365 days a year. If your really concerned have a perk? test done. Across the street they added on to the old folks home. When it came to putting in a perimeter drain they had an engineer do a perk test and they don't need the drain and there soil is exactly the same as mine. I would damp proof your foundation like mike said and when you put your drain tile in wrap it in filter cloth otherwise it will just fill with sand.

4. 
   Tripper | Feb 25, 2002 10:07pm | #8

   *A few more questions to throw into the mix...Is there an advantage to having an exterior AND interior drain if they're both below the slab? I've heard yes because the exterior is far more likely to fail. So why not just put in an interior only? I'm guessing because maybe only the exterior drains take care of backfill saturation and groundwater spikes but when they fail you've at least got ground water protection remaining.Can you run both exterior and exterior drains to the same sump pit? I don't see a problem. Running to daylight is another issue.If you use washed gravel under the slab and a perforated sump liner, can you skip the interior drain pipes? I'm guessing yes because if you put a bathtub in a swimming pool(no I haven't tried it) and push down on it(simulating ground water pushing up on slab)the water will have no trouble finding the "drain" on it's own.I guess I'm kind of like Tim's dad. If my wife catches me staring off into space she usually says, "you're thinking about foundation drainage again, are'nt you?". I'm just interested in giving my customers a good product for their money and also I like sleeping peacefully at night. Hundreds of extra dollars spent in the big picture of an entire house seems like peanuts for these rewards. Thanks for the input guys.

5. 
   Boss_Hog | Feb 25, 2002 10:44pm | #9

   *Talking about foundation sealers makes me think of a guy I saw sealing a foundation last summer. He was using a spray-on sealer - pump in the truck with a long hose and some kind of spray gun. I hadn't seen it done before so I asked if I could watch a minute or 2. I noticed he was hitting the small ridges twice wherever the foundation forms had butted together. When I asked why he was doing that, he said: "I always hit the seams twice"Guess it never ocurred to him those weren't seams in the concrete, just a little ridge that had seeped out between the forms.

6. 
   John_Bs. | Feb 26, 2002 04:19am | #10

   *This is one of those questions with a thousand answers but here is my two cents. We build with mostly poured foundations in an area with all types of soil conditions from course gravel to solid clay. In a poor drainage soil like clay I always use a exterior drain tile in washed stone with fabric. The best method uses a backfill protection drainage board similar to that used in commercial construction. This serves 2 purposes. One, it protects your waterproofing membrane from damage as you backfill any stone or rocky soil against the wall, and two, it provides an easy straight path from grade directly down to the footing drains. The drains in this case would go to daylight if possible, or to an interior sump crock set in washed stone to be pumped. We also use stone under the slab, a minimum of 6 inches. For a real wet site with a lot of subsurface water, consider a membrane waterproofer such as Rub-R-Wall. It has the ability to stretch an amazing amount unlike cheaper asphalt coatings. This is sprayed on. I think the reason the apllicator was double coating the ridges wasn't because he meant they were seams through the concrete, but because as they are sharper uneven surfaces they require a thicker build up of waterproofer for good coverage. Don't forget to consider radon problems also. We usually install interior drainage piping in the washed stone with provisions to hook onto one end of the pipe for future radon mitigation if required. Keep this end sealed until determined if this is needed. It's a lot easier to do at this stage than later.On a lot with good drainage such as gravel, the above is overkill. We would usually run only interior perimeter drains to the sump crock, forget the exterior, unless there is potential for subsurface water. Remember that any water buildup under the surface can exert tremendous pressure on foundation walls, causing cracks that can be more serious than just potential leakage so the idea is to give water a path to follow.

7. 
   Mad_Dog | Feb 26, 2002 07:22pm | #11

   *Local code on the house I built last summer required interior and exterior drain tiles next to the footings, with passages between them or ending up in the sump crock. I was able to convince the inspector that the sand we built on would satisfy the requirement for crushed stone. This house was built on sand, with no stone at all, except under the walkout frostwall, which reached a level 5 feet lower than everywhere else.

8. 
   diddidit_ | Feb 26, 2002 08:08pm | #12

   *A house going up down the street from me went in with no drains inside or out, unless I missed 'em. This is western Michigan, though, within 5 miles of Lake Michigan - nothing down there but sand.did

9. 
   Tim_Mooney | Feb 28, 2002 05:48am | #13

   *I want to say thanks guys as you reinforced my thinking. You are relieveing the floor pressure,if it exists, and venting it out. I will have to look at it again but I dont think the code I use calls for it. Could be my over sight. But I remember Mike said the inspector wanted it.