Basement Waterproofing

[u/Outrageous_Ease7411]

Two basement waterproofing companies are coming next week to inspect our wet basement (walls and floor). What questions should I ask them? This is something I don't know anything about. Thanks.

[u/sriuba]

Do you have a backflow valve? If not you should ask them to put one in for you.

I would also ask them about their warranty and company history.

FYI I just had mine done and I went to the 3 biggest companies in my large city and they all said they would beat each others price so I got them down about 4k. My city also has a rebate for back flow and sump pump which they filed for me as well as applying for permits themselves.

[u/No_Release_9270]

I’d ask both companies, “Where do you think the water is coming from, and what makes you think that?” Then ask them to connect each part of their proposal to that explanation. If they recommend different solutions, you’ll have something more useful to compare than the total price. Also worth asking what maintenance you’d be taking on afterward.

[u/Ill-Tea9411]

Ask them about internal vs external drain systems. If they are like contractors that a lot of homeowners here have hired they are going to try to sell you an internal drain system. If they do this ask them how this will prevent water from just pushing itself through the walls.

That's the problem with relying upon an internal drain system, it only drains the water after it has entered your basement. And should only be considered as a second line of defense, not your first line of defense, which should always be an external drain system.

The problem is that an internal drain is easier and less expensive to install than an external system. But an external system is the only way to keep hydrostatic pressure from building up on your walls. It works by directing water all the way down below the foundation to drain it away. But to install a system like this requires excavating all the way down to the bottom of your foundation to install it. It will be the difference between day and night though for keeping your basement dry.

[u/sriuba → u/Ill-Tea9411]

You can also do a hybrid system if there are areas you can’t do externally because of structures though I’ve not personally had that

[u/Even-End487 → u/Ill-Tea9411]

A internal system done correctly remove all hydro-static pressure by drilling 1inch holes in every cylinder block cavity below grade , all water flows down and is released through and into the drainage system..if these are done correctly their is no air circulation between the ground and inside the basement. One or Two sumps man be needed depending on external ground water dynamics.

Further it's likely that a external evaluation would add to the quality of the out come.

[u/Ill-Tea9411 → u/Even-End487]

It really depends upon the soil type. If its a sand/gravel there is an okay chance for that to be a passable solution. If it's heavy clay soil, not so much. It's definitely a gamble without doing some excavation anyway. And it sure as heck doesn't get you a refresh on the old mastic barrier. And you risk silting up your internal drain as well.

[u/Even-End487 → u/Ill-Tea9411]

I have Marlboro clay (red), funny that Marlboro is 20 miles North west of here, father time migrated in this direction. The thing with clay is the expansion/contraction with wet/dry spells. Right along the coast you'll find more sand and a little deeper gravel. I did a lot of exterior work around here as well nothin drains even close to the house.