Crawlspace Partially Excavated – Your Help Needed!

Crawlspace Partially Excavated – Your Help Needed!

Hello, I have a few other posts out there but I finally dug out the perimeter of my crawl space. The space is un-vented and was built 6 years ago to build an addition which went up before we bought the house. The walls are block, all but one or two at the top are below grade. The floor has a poly layer covered by 6” of gravel. The poly layer stops short about 6” from all the edges, making for a very damp perimeter and overall a damp crawl space.

We pulled all the rock away from the edges, exposing the poly layer and mud below. There was a corrugated black weeping pipe that ran around the 3 exterior walls but it didn’t go or drain anywhere. It was open on both ends. We also noticed two holes in each of the exterior foundations. It appears these go outside but then when I look in it just looks like mud on the other side.

My questions are:

- What are those holes for?
- What was the weeping pipe for if it didn’t go anywhere?
- What do I need to do to make this right?

Thank you!

Before pulling all the rock away:


After:

 

I'm always an advocate for exposing & sealing the block from the outside first. Then decide if anything is needed inside. I can explain how that's done if you are interested. Most people don't want to bother.

 

Flexible, perforated plastic pipe is never a good idea for providing long-lasting drainage solutions. It's difficult to install perfectly straight, without undulations, such that fines working their way through the openings will collect inside at all of the low spots, slowing down the passage of water. Especially when installed without any mesh fabric to keep the fines out, as yours appears to be.

Time to yank everything out and properly install some rigid perforated pipe, inside of a mesh wrap. And use washed rock instead of sandy gravel.

 

OK, You say the tile goes nowhere. Oh yes it will and you can easily show it the way. It looks as though you are going to need sump pump. So that the pump can be managed the proper place for to dig the sump will be inside the foundation. The pipe looks to be even with the top of the footing an you are going to finish the loop surrounding the footing and then use the 4" holes the builder left through the footing and connect to a run of tile on the inside of the foundation/crawlspace. Pick a spot for your sump pit and get it installed one inside pipe will connect to the sump pit on each side as you install the sump in the tile run inside your footing. That system will be fine and the two holes through the concrete will serve to allow the tile to equalize and collect ground water in and outside the footer.

Now if your immediate terraiin would allow you to simply dig a ditch for pipe to drain to daylight, than the sump pit and a pump remain undecessary. Gravity moves water forever so that beats replacing a sump pit every 4-5 years

I like the strait white plastic weeping tiles (holes down with a foot of gravel over pipe in and out) also. I don't think it is necessary to strip and replace the black corrugated that is already in place however.

bs5

 

Sump pump? Why would you need a sump pump if you stop the water entering from the outside? The only way a sump pump would be needed is if the water table is high. Is that the case?

 

Water moves laterally and can come up by capillary action so the soil can be damp or wet (depending on the soil type) even if it is above the water table.

If the soil is wet, a sump and pump will drain the excess moisture out, reducing the humidity. Eventually a sump pump will run infrequently once the exterior problems are corrected, but will be available when needed.

Dick

The cheap, flexible perforated pipe is trash and very easy to install improperly. Rigid perforated pvc is more "idiot-proof" when it comes to installing. Install in a trench lined with fabric and with 4" of a sand and pea rock mixture under it and around it to maximize the moisture collection from the soil. That is a system (without the new fabric) that was been used for decades.

Use solid wall pvc for moving the water away and not to spill collected water into other areas.

 

Hi Pulpo,

The original poster says the tile line goes "Nowhere" It needs to go somewhere and that would be a sump or preferably to daylight. If ground water has enough pressure outside a block wall to register to the top of the fourth course of blocks on the outside, the same amount of pressure exists on the inside of a crawl space or basement wall.

Hydraulic pressure from the outside pushes inward against a foundation wall and is sometimes a factor of bowing basement walls inward and basement floors can even be pushed upwards. This can have a cumulative effect over time The water pressure seeks the path of least resistance and enters basements from the soil throughout the earth beneath a floor and walls and through cracks seeking it's own level. Proper tiling reduces the pressure and reduces levels in the immediate area. This makes for a dry foundation and the water level can't rise above the tile/sump system inside or out of immediate area.

Outside wall treatment is necessary but it addresses effect not the cause. If the original poster has this type of a high water table(even if it is just seasonal) a good tile system addresses the cause.

bs5

 

Oh, one more suggestion. The picture submitted by the original poster shows me that that block wall has got water sitting inside. If you tile that foundation like it looks as if you should, you need to drill some holes through those blocks on the bottom course to allow the water to run out. That bottom course is saturated.

On the outside of the block wall make sure you drill a hole through the bottom course as close to the footing as possible (through mortar bed joint) and for safety's sake drill another about 3" up or just below the floor level.

Then you want to make sure gravel rises high enough above those holes that the water can escape the walls and drain to the outside tile through the gravel. Cover the gravel on top with geotextile cloth to keep sediment from plugging holes.

For a dry basement (not necessarily a crawl space)you woud drill the inside as well but provide a tube from the hole to the tile gravel inside tile so concrete can be poured across the footing for the floor with out blocking drain from wall.

bs5

 

you really haven't given us quite enough...
how deep is the crawl versus the outside grade?
Where are you in the USA?

Other posters are right - it appears your block is holding water inside. The holes? Not sure, probably some kind of low-point drain to let water out but never done right?
The perforated pipe should drain somewhere. Lots of ignorant builders somehow assume if you put it a pipe the water 'magically' disappears.
Is your lot very flat or is the crawl sunken down in the ground? Probably need a sump pump. PLEASE use a proper sump-pump basin, don't just stick it in a hole.
So, dig out the current pipe and throw it away. Anywhere you even THINK water is coming in, you'll want a french drain installed. Dig your trench down to approximately beside the footing level. Install pipe and surround with stone. The type of stone will largely depend on where you are. 'pea gravel' might be appropriate, or what we would call #57 stone.
Pipe choice is honestly preference. Take care and the black plastic pipe can be purchased slotted and installed cheaply and easily. Don't sweat putting a fabric around the pipe (although lining the trench first is an okay idea. Putting a fabric 'sock' around the pipe to prevent fines from getting in often leads to the sock being clogged with fines. In a seepage situation like in most crawlspaces, it's acceptable to let the water in and if the corrugations get some silt in them, so be it.
Then, be sure to have the pipe exit the foundation and gravity drain via a SOLID walled pipe or into your new sump pump basin.
then, lay a strip of poly around the perimeter and pin in place.

 

I still don't get it. How is the water entering in the first place & why isn't that the main focus?

 

For Pulpo,

Let me take one more crack at this. Think of it this way. Take a common garden hose and you take one end and allow a buddy to stretch the hose out and grab the other end. Now you are holding your end of the hose at your waste level. your buddy has stretched the hose out the fifty feet and maybe he is at a spot that is two feet lower than you. He is also holding his end of the hose off the ground by three feet. Using a funnel you can start filling your end of the hose and when the water level is just perhaps an inch below the end you stop.

Now your buddy has stretched the hose out and while he is perhaps 50 feet away he has to raise his end of the hose practically to his nose level to keeps from spilling the water. Now the water level is perfectly level one end of the hose to another because water seeks it's own level.

Go ahead now and build a foundation wall between you and your buddy. and while you are at it apply all the water proofing to the sides of that wall you want. In the right kinds of soil sandy gravel or even certain loams water pressure pushes to seek it's own level. Let the hose used by those two hose people droop below the footing like a water pipe trap. Granular soils allow that to happen just as the hose did. Go ahead and shoot that water level in that hose with a new laser transit. It's perfectly level because of the water pressure created by the water seeking it's static level through the soil. That waterprooofing did nothing to prevent the water from getting back to it's level because it pushed up from below the walls and into the interior.

An excavation for a foundation structure is like digging a swimming pool. At certain sites the ground water table is a problem. Collecting and pumping water an excavated sites at some spots can temporarily lower the level of ground water. Maybe this only has to be done in the Spring of the year. Of course it becomes a maintenance item so you have to maintain a pump or constant diversion by running the water to daylight. It's just the way it is.

If you could apply a tee and an open boiler drain at the low spot in that hose and eject the water from that particular area you could practically eliminate the problem. The sump acts just as the boiler drain does in this example.

Whew! I'm done, I hope this helps. Sorry about all my rambling on this thread.

 

I have a complete understanding about water tables. I've done plenty of foundation waterproofing jobs but not once did the original poster mention a high water table. How high is he water table in his area. Just because the previous owner decided to try to solve the problem from the inside first, doesn't tell us where the water table is. People add sump pumps many times for the wrong reasons.