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Rick, General Contractor
Category: Home Improvement
Satisfied Customers: 20769
Experience:  Licensed construction supervisor with 35+ yrs. experience.
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Hello, I have what I believe is terracotta block as the

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I have what I believe is terracotta block as the foundation for my basement. I am planning to excavate 4 inches under the current level to put in some type of drainage system that will make the water flow around the house.

What I probably have to do is use a sealer after disturbing that area. What is available readily and what can i use as a novice DIY to this topic.

Welcome, my name is XXXXX XXXXX I will do my best to help you with your issue

It's not clear to me exactly what your plans are. First my concerns; if you mean you want to excavate below the bottom of the foundation you should avoid this and stay above the bottom of the foundation. I don't know what or why you would want to use "sealer" (on the foundation?). Digging a drainage trench won't disturb any foundation seal.

You would start with a layer of gravel then lay this type of pipe on top of the gravel.

The pipe should be wrapped in drainage fabric to keep out silt and sand or you can use this type of pipe . The drain should be sloped so it drains towards the outlet. Next cover the pipe with crushed stone up to the grade level (if the pipe is near the surface) cover with 6" to 12"of stone (if you are well below the surface) then cover with soil. If you cover it with soil the stone should be covered with landscapers fabric to keep out silt and sand

Customer: replied 3 years ago.

Hi Rick,


I guess I mispoke. Alongside the foundation I have a sidewalk. The problem that I have is that the slope is toward the house. The water runs along the foundation, then turns 90 degrees and continues against the foundation. I am guessing water running against the foundation...even when it flows is not a good idea right? (otherwise I will just let it continue to do this) or is there something I can put around the house so it is traveling against that material)


I am glad you asked what exactly we are doing because now I am not sure. He was talking about using pvc pipe, but then I am wondering how is the water entering.


To get back to what I understand of the proposal, he stated that he has to dig 2-3 inches below the present level so that it will be level with the sidewalk. We are then going to have it make that 90 degree turn.


He said exposing the 2-3 inch of the foundation will require a sealer. I believe you said I don't need to seal that area? He was planning on using Thomson seal. My concern is I dont want to use something that will mess up the foundation. It is a 1929 home and my first home (9 months into it).


When all is said and done the water goes to the other side of the house where it goes into an underground drain that goes to the street? (We will figure this out when we use a snake to take out roots and dirt that filled the pipe..for now the water pools and then eventually goes away after a few hours)

There is no need to seal the foundation and sealing only the top few inches is pointless. If you aren't getting water in the basement then I don't see the need to do anything unless you get so much water and rain it's starting to errode the foundation which I would not expect. If you want to improve the drainage then the type of pipe I linked in my first answer is what would be used even if it's just below the surface. And you must use fabric to keep out the silt and sand. You can't snake out a pipe that's full of sand
Customer: replied 3 years ago.

Ok I will let him the guy know what you said. I am not getting water coming through the basement, but it is damp and wet sometimes.


At some point I do want to waterproof the exterior of the terricotta, so just for my information, even though you say it is pointless to do it for this application, what can I use?

The time to seal the exterior of a foundation is before it's back filled. There is no cost effective benefit to sealing the exterior now since the only effective way to do it would be to excavate the entire exterior of the foundation down to the footings. Unsealed terracotta has literally lasted for centuries. You can seal the interior with one of the Drylok paint products if you want.The only clear terracotta sealers are made for floor tile not block.

Customer: replied 3 years ago.

ok. Was having trouble getting an answer about how to seal terricotta. My basement does have drylock, but I read is not a good idea because it :


"Water proofing terra cotta block foundation walls on the interior is NOT a good idea as it effectively traps moisture that has migrated from the surrounding earth in the blocks and prevents it from evaporating. It is much better in terms of the longevity and structural integrity of the blocks to allow it to breath as this minimizes moisture content in the material."


They recommended Thoroseal, but I am unable to get that from my local HD and it seems to be a pain to work with.


The products you mentioned unfortunately are not available to me. I guess I will purchase something like this:





I'd be very skeptical of any advice on a DIY chat room. Terra cotta is impervious to water. Yes water can infiltrate the block from the outside but it won't damage the terracotta. Have you every seen a clay flower pot damaged by water? This advice is ridiculous. Thoroseal is another option but it's not significantly different than Drylok. The purpose of sealing a foundation inside or out is to keep water out of the basement not to preserve or protect the foundation. If foundation material needs protection from water it shouldn't be used for a foundation. The flex drainage hose you link is also ok if a bit more difficult to slope uniformly. You still need to wrap it in fabric or it could fill with sediment.

Customer: replied 3 years ago.

Alright Rick,

Thanks for the information.


I will see if I can get substitutes for the materials you suggested. As for the one I suggested, I guess you want to be even more cautious about the dirt; it says, "The pipe is joined with either a cleated bell, split coupler, internal coupler or snap coupler and is soil-tight."

I guess you can't be over cautious?


You just want to do your best to let the water in and keep the dirt out of the pipe. Once the pipe fills with dirt it's useless. The landscape fabric I linked (or something similar)should be available at any big box store, garden or home center.

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