Best Product to Seal a Block Basement Wall.

[RSKY]

We are preparing a sixty year old house to sell. The basement walls are of concrete blocks. After a heavy rain they seep a small amount of water thru some cracks and thru the blocks themselves. What is the best paint on product to seal the walls and what do I use to seal cracks?

 

[Fxfymn413]

How wide are the cracks? I have used hydraulic cement to seal cracks about 1/4 inch wide.

 

[dlctcg]

If the block is in good shape then IMHO there is no better product that we have used (that can be easily applied by anyone) then Sani-Tred.

Not the least expensive by any means but if the surface is properly prepped & application done via the instructions we have never had it fail & the finish is nice. I believe the oldest project we have done with it is going on 20yrs ago. Our attached garage floor used to wick water right through it... completely dry for the last 9+ yrs...

Here are pics of a project completed 3+ years ago... This is a cottage on a small lake that would have standing water in the basement multiple times a year making it completely unusable; the owner tried Dry-Loc (it Failed / we had to remove ) then they had exterior drainage professionally installed (didn't work) water was coming through the block. When we told them we would seal it from the inside & we would finish the basement as usable space & if it leaked we would pay for the damages... they looked at us in complete disbelief.

Still Dry - Some Pics - These are all from the same corner of the basement...



Walls Prepped prior & 1st coat of Sani-Tred



Typical cracks in the block (1st coat rolled on)




Cracks & flaws filled with LRB




Final Coat of Sani-Tred




Part of the finished basement

 

[grsthegreat]

problem is...this just seals water inside concrete and blocks, eroding away the rebar. this is just surface repairs. you need to remove all backfill from walls, clean and waterproof the actual walls.

i used to do this for a living years ago. i would prep cleaned wall with layer of ThoroSeal grey , then a second layer of ThoroSeal white sealer. then install a layer of Bituthane 1/4" self adhering membrane over a coat of extra adhesive. Then install a 2" Styrofoam protector board to prevent rock damage, add a french drain and install french drain rock.

i did this for many years, and have never had water infiltration.

i did it on my own house 26 years ago for basement. not a whiff of mildew many years later.

i tried to have my buddy that is building a new house do so on his foundation, but hes a lazy sack. he just brushed on some kind of thick waterproof paint, then backfilled without french drains. house is 1 year old....leaks like a sieve. cant fix stupid.

 

[Bill Guenthner]

You cannot properly patch a leaking concrete block basement wall from the inside. Anyone who says otherwise is mistaken. As already stated above, you have to do it from the outside. Without a proper repair you’re going to have to disclose the leaks.

 

[dlctcg]

So I will agree & disagree with the above statement...

Yes you can dig all the way around your foundation... disturb the soil... disturb the landscape... & seal from the exterior of the foundation... & it will solve the problem.. if done properly... but that is not what was asked...

"What is the best paint on product to seal the walls and what do I use to seal cracks?" (& for the occasional "after a heavy rain they seep a small amount of water thru some cracks and thru the blocks themselves"), we are not talking about a house that is submerged in a pond. We are talking about a basement that under normal conditions does not see water (according to the OP); which means, normally it drain well & does not see interior leakage. This tell me the block will not be completely saturated under normal circumstances & will dry out after unnormal circumstances...

You are selling... right???

I still do this for a living, 30+ yrs through out NE & depending on the situation there are more than one resolves... (again I don't disagree with the above) but to answer the OP's Question... Sani-Tred works... (it has been used in underwater tunnels (from the interior) & in ships (not saying which gov. agency.., call them)... All I can say is in our experience 20+++ yrs no failures... (and I have NO CONNECTION to them.... we were lucky to stumble on their product many (many) years ago...)

I do agree that exterior sealing does work & is the correct solution (we do it)... but not the only solution... I was answering the OP's question as it was asked....

Oh, & I don't know of a single state that you have to "disclose a leak"... If it is not leaking (& I think we work in 3 of the crappiest state to be a contractor)...

 

[Bill Guenthner]

Oh, & I don't know of a single state that you have to "disclose a leak"... If it is not leaking (& I think we work in 3 of the crappiest state to be a contractor)...

If all you do is “seal” the inside surface of the block then it is still leaking. More than that, concrete block that is being repeatedly infiltrated by water over years will be structurally compromised, and they know that it’s happening so they should disclose it.

 

[MossRoad]

If all you do is “seal” the inside surface of the block then it is still leaking. More than that, concrete block that is being repeatedly infiltrated by water over years will be structurally compromised, and they know that it’s happening so they should disclose it.

Personally, if I were going to stay in the house, I'd find if the problem is high ground water, or, bad drainage after rain. It sounds like small leaks after rain. That indicates poor drainage near the house. We had this problem in our first house. Heavy rain = water seeping trough the block. So I dug a trench 2' down and 2' out from the house, smeared mastic down 2' on the foundation, laid a waterproof fabric onto the mastic, and formed a U-shaped channel with the fabric in the trench. Then laid some stone and a perforated pipe in a sock at the proper drainage angle into the fabric lined trench and backfilled with stone. At the end of the pipe, I turned it 90 degrees away from the house, then into a drywell made of two 55 gallon drums with open bottoms filled with rock. Then added a nice 6x6 pressure treated edge along the stone to keep the grass out. And most importantly, I made sure my downspouts ran to areas that were sloped away from the house, and I regraded the yard to make a swale to carry surface water away, not towards, the house. From that point on, any rainwater on the surface would flow away from the house, and any water that splashed onto the side of the house would run down into the trench, through the rock, the correlated socked pipe, and into the drywells. Never had the problem again.


However, that's not what the OP wants to do.

He's asking how to seal it from the inside.

 

[Dwellonroof]

I'm looking for a solution for a block cistern which are very common in this area of Ohio. It's not feasible to dig out and replace mostly because at least one side is part of the house foundation.
I did use a product called Quick Wall for one cistern about 10 years ago but have since moved on and I don't know how well it held up but the 4 years I live there we never had any problems.

 

[gstrom99]

Either leave it alone (and disclose the "occasional" issue to the buyer), or seal it properly from outside, IMHO. Fix the drainage too (gutters, downspouts, foundation drain), that's causing it to leak in the first place.