How do I fix water getting into my walkout basement from my patio?

Jerry Hilscher
by Jerry Hilscher

Hi, water got into my basement from the patio outside my walkout basement of my 40 y/o home. The flashing applied 40 years ago rusted away. Big box store advised flashing and sealant. Unexpected storms hit last night after removing siding and installing flashing, water came in. Did I do something wrong, did I use the wrong flashing (I have been told that the old flashing wasn't 'L' shaped, but can't tell from the old stuff). What do I do now. We have unexpected company coming and will need the basement space, plus I will have to remove moldy dry wall too, so need to fix this correctly.

What I found after removing 4'x8' panel siding.

another before pic

water after storm

my repair with 4" L type flashing and flashing adhesive/caulk

another after pic

  6 answers
  • I'm wondering if you need to regrade the ground outside to have the water move away from your house. I would call a professional.

  • Vimarhonor Vimarhonor on Aug 22, 2021

    Hello. As it an unusually heavy rain?

    Sometimes water tables get saturated after significant storms. Your soil quality can affect this.

    We moved into a home and 6-8 months later the basement started flooding. It was an awful situation. We thought the deteriorating septic system played apart.

    The best thing to do to prevent water collecting around your foundation. Absolutely make to make sure your gutters are extended and free-flowing. The hydrostatic pressure of water collecting around your foundation can find its way to seep into the smallest cracks in your foundation.

  • William William on Aug 22, 2021

    Did you put any sealant under the flashing?! If not use some roofing mastic under the flashing. Embed the flashing into the mastic, push it down as you nail it into the joists to hold it in place. Use the mastic to seal any gaps. This is a temporary fix. You may need to grade the patio so water flows away from the foundation. Installing a french drain to divert water away from the foundation would help

  • Robyn Garner Robyn Garner on Aug 23, 2021

    Did you remove all the dry rotted wood prior to installing the new flashing? If not, you installed on top of a wet, unstable surface that could fail when exposed to more moisture. Yes, you must have exterior grade sealant below the flashing prior to installation screws as well as sealing all screws in place.

    It looks to me like you've Chattahoochee finish over cement at the leak location outside. You could potentially powerwash or chip off that pebble epoxy finish which would lower the rim where it leaks. If you can chip enough away to create proper runoff to the yard the flooding could be eliminated with resorting to excavating a French drain.

    Personally, I would not try this chemical method

  • Gary Woolley Gary Woolley on Aug 24, 2021

    Definitely check the grade/pitch of the surrounding surface (gravel) and make sure it is running/sloping away from your walkout area. The water has to have a place to flow away from your house, foundation and walk-out. It could be that over the last many years, you have added the gravel to your outside walkway by your walk-out. Over that time the gravel will collect silt/impurities, etc and not let water to flow through it to a lower elevation. Try raking the gravel away from your walk-out and make sure the pitch is going away from your door to a lower spot in your yard.

    Water WILL find the path of least resistance and flow that way. My bet is the water flows towards your walk-out easier than towards your side/back yard.

    Lastly, you could install a french drain to move the water away from that area.

    Hope this helps, Gary

  • Mogie Mogie on Nov 14, 2022

    You need to make the walk out area higher or at least be able to drain it at the least. Many folks have a drain that gets the water drained off before it reaches the walk out.