{Basement} waterproofing contractor suggestion.


  #1  
Old 11-27-05, 09:36 AM
jim7485
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As a last resort, waterproofing contractor has suggested...

10 years ago, I made a mistake that has haunted me. Acting as my own contractor the basement was dug about 18 inches too deep. We added three layers of block above the pour. Exterior grade is above the joint where the poured wall meets the blocks. To make matters worse ( ) I installed a brick paver patio on the back and side of the house. When it rains really hard, water hitting the pavers does not run off, but seeps down where it eventually enters the basement at the pour/block joint. The leak is 40 feet long. As a fix, a contractor dug up the area and sealed the joint with tar and a membrane. He also added a sock pipe that spans the 40 feet which is connected by 4 stand pipes running down to the bottom drain tile. Pea gravel surrounds the pipes. This system lasted 3 years under some very heavy storms, but has since failed. Next, the contractor injected the 40 ft joint with expanding foam, but I really don't think it's made to fill a block, just a small crack. Water still enters, but at a higher spot on the wall. He has proposed drilling several core holes at the joint to collect the water and send it to a drain via pvc pipe. Any thoughts on this system? I don't want to dig up the pavers again, so whatever we do has to be from the inside. Basement is finished, but partially torn up for this repair.

Thanks in advance for any thoughts.

jim-
 
  #2  
Old 11-27-05, 12:41 PM
Join Date: Mar 2005
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{Basement} waterproofing contractor suggestion.

I have few questions to get a better picture of the situation.

1. What type of soil do you have around your basement? -The natural soil and not the backfill.

2. What is the general slope away from your house and do you have downspout exteneions (how long)?

3. Are all the interior walls of the basement dry at the junction with the floor?

4. What is the slope (inches per foot) or drop of your patio from the house to the edge?

5. What was the coating put on the block before it was initially backfilled?

6. Is there a crack between the block and the concrete on the inside?

7. How do you know where the water enters the wall or are you assuming it enters where it shows up on the inside? How much water is leaking in?

8. I assume your patio is made up as a 60mm (2 3/8") interlocking pavers, 1 to 1 1/2" sand setting bed and a 6" compacted base. Was the sand vibrated into the joints?

Forgive the questions, but they are necessary without a lot of pictures. It takes something very strange to cause a lot of water to leak in with virtually no pressure behind it.

Dick
 
  #3  
Old 11-27-05, 01:12 PM
jim7485
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1. What type of soil do you have around your basement? -The natural soil and not the backfill. -- Soil around the house is heavy clay, back fill is pea gravel/sand and probably quite a bit of the clay.

2. What is the general slope away from your house and do you have downspout exteneions (how long)? -- General slope around this area is flat near the house, then slopes toward the house from about 10 feet away. I spent a small fortune on a drain for the downspouts. They all funnel into a 4" solid pvc pipe system that eventually works its way from the house to city system.

3. Are all the interior walls of the basement dry at the junction with the floor?-- yes, always dry.

4. What is the slope (inches per foot) or drop of your patio from the house to the edge? -- it appears flat to me, but may slope slightly away. Patio is about 16 feet square + a walkway that runs another 25 feet or so. Both butt up against the house.

5. What was the coating put on the block before it was initially backfilled? -- some sort of black goo, damp-proofing probably.

6. Is there a crack between the block and the concrete on the inside? -- yes, that's where the water enters. It's sort of difficult for me to replicate a heavy rain, but if I let a hose run for about 45 min, water starts to enter in the same spot every time, no matter where I put the hose. A hose running at the back of the house will cause water to enter first around the side, some 30 feet away. Within minutes, the crack leaks over its length but seems to start in the same spot every time. Water must be getting behind the 'repair' and running horizontally.

7. How do you know where the water enters the wall or are you assuming it enters where it shows up on the inside? How much water is leaking in? --I have tested it and watched where it enters, twice sitting in the basement reading a book till it starts. An hour's worth of leaking will produce 5-8 gallons of water on the floor.

8. I assume your patio is made up as a 60mm (2 3/8") interlocking pavers, 1 to 1 1/2" sand setting bed and a 6" compacted base. Was the sand vibrated into the joints? --Pavers are squares and rectangles installed as you describe. I even specified polymeric sand which sets up hard after it gets wet, in the hopes that it would help. It was vibrated into the joints. Like this stuff: www.supersandbond.com

Thanks for your reply. Hoping you can assist.

jim-
 
  #4  
Old 11-27-05, 06:33 PM
Join Date: Mar 2005
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{Basement} waterproofing contractor suggestion.

Jim -

I think I have a better idea of the problem now.

First, you should be able to patch stop or slow the water entering the basement. One of the most reliable methods is to open up the crack between the poured concrete and the block. Make the opening a "dovetail" joint - larger inside than the opening to provide a keyway. Fill the joint with a hydraulis cement (Thoroplug or similar). Force it into the joint. Even if you stop the "inner" leak, you will still have water within the wall. I would fill as much of the crack as you can while you are at it.

My guess is that the water in the block wall could be entering anywhere around the house and accumulate in the wall or cores of the block. It leaks at one point now, but could leak elsewhere eventually if that leak is plugged. You stated that it leaked at the same spot no matter where you put the hose. Block should be laid with a ful mortar bed for the first course, but frequently contractors intentionally do not mortar under the cross webs to permit water to flow laterally on top of a footing to a drainage point.

The black "waterproofer" was actually a dampproofer, but this type of product loses it effect over time. It is probably allowing water to get to a leak somewhere. Your grading and soil type permit the water to stay in the area of a house.

A basement in clay soil is just like building a home in a swimming pool with water all around it. You probably had a construction excavation 3 to 10 feet outside the exterior of you basement walls. Apparently, the lower drain tile is removing most of the water, but some of the water is apparently "perched" on some impervoious soil (clay over backfill?) around the house, which causes the accumulation.

You propbably do not have much water percolating through the pavers, but it can easily accumulate in the granular soil under the pavers and possibly under a sidewalk. Water could also be fed to the soil under the pavers at the surrounding area. This can act like a spring or french drain operating in reverse toward the house.

This is all just a supposition based on what can happen when you build on and in impervious clay - water is collected.

You could excavate close to the wall around the house and look for any signs of a spot where water could enter at or above the level of the poured concrete. If you see anything, chip it out and patch as you did on the interior. As much as I hate the black junk because it is difficult to remove or recoat with better materials, I would apply some kind of a compatible material to try to close up the "outer" leak. If you can provide a way for any water trapped under the patio to drain off, I would do that.

This is just my best guess. - Good luck. Think about it and see if any of it applies to your situation.

Dick
 
  #5  
Old 11-28-05, 07:41 PM
jim7485
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This is some great information that I had not considered. We had a strong rain tonight. As usual, the rain started on the side of the house. I sat and watched it, so have a good idea where to look. The expanding foam repair seems to have pushed the entry point horitontally down the wall. The foam may be working after all. There's only about 8 more feet of horizontal joint that has not been injected between the current leak and the garage. This area has a planter box between the house and the pavers, so repair from the outside seems possible. What tools would you suggest for the interior dovetail joint? Can I use a hand held power chisel of some sort? Maybe an angle grinder? Thanks for your advice- very helpful.

jim-
 
  #6  
Old 11-28-05, 08:13 PM
Join Date: Mar 2005
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{Basement} waterproofing contractor suggestion.

Jim -

If you have water around a basement, it will flow laterally to accumulate or find an entry.

The "dovetail" is commonly done at the joint between the floor and wall (much harder). A hammer and chisel will work or you can make it pretty and perfect with a grinder (dusty). The main thing is to make the interior larger than the opening to keep it in place and allow any expansion to wedge the plug in place.

Just look at the outside and try to visualize there the water is coming from and where it is and accumulating and going to.

Good luck.

Dick
 
 

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