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attn: Tscarborough, Hurricane Sandy, basement repair, point, parge, insulate

1398 Views 4 Replies 3 Participants Last post by  concretemasonry
hello. I have never posted to the forum before, but I have followed various threads for a long time now. Advice from all would be appreciated, but the topic seems up Tscarboroughs alley.


  • House is located in Rockaway Beach New York. Said to have been built in 1930s
  • The formerly "finished" basement was thankfully destroyed during Sandy (mold farm), and I need to repair/refinish.
  • The interior foundation walls in the basement are exposed, and I would like to repair and insulate.
  • One length of the exterior foundation wall is now exposed due to a waste line repair. I am considering insulating and waterproofing this exterior wall.


  • The soil is primarily sandy. The water table is 10' below grade. We experience all seasonal extremes.
  • The basement is a full basement--with 2' above grade and 4.5' residing below grade.
  • The basement doesn't have flooding issues. During high tides and heavy rains, however, the slab does show evidence of moisture (darkened concrete) There is no standing water.
  • The foundation is a block foundation. Smooth on the interior. Split face on the exterior.

  • Waterproof exterior wall? On the one length of the exposed exterior foundation--> place drainage gravel, weatherproof the foundation with a blackjack-type waterproofing. (I figure this is the best option because of the Splitface nature of the block). Then I was going to throw up some rigid insulation then back fill.
  • On the interior, I was thinking of pointing, parging, directly attaching the rigid (as suggested by DOW), and then parging over that.

  • When pressure washing the interior walls, it seemed like the original parging that was hidden behind the recently demoed stick-built/finished walls is softer than the repairs that have been executed around, say, the boiler and other locations in more recent years. It has a very gritty, sandy and whitish color. It was in mostly stable condition. This made me wonder if the parging was lime based. The mortar in the joints, however, feels if portland based.
  • Some of the mortar joints need repair, but I am unsure what type mortar is best in this application. Because of the sandy soil, I imagine it needs to remain flexible? But since it is structural and below grade, it needs to be strong enough as well.

  • I am also unsure what to use for the parging. The relatively dry nature of the basement--in comparison to the other basements in the neighborhood-- lead me to believe that they took "breathability" into consideration when they parged long ago. The basement gets humid, but nothing that can't be handled by mechanical means (dehumidifier). I do not want to seal this breathability and cause internal damage to the block.
  • DOW says I can attached rigid to the wall directly. Will this create yet another seal through which moisture will be unable to escape? Or is rigid breathable. I will then have to parge over the rigid. What do i use for this? Should I fir out a wall with metal studs allowing for a vapor barrier instead? Is the combination of the slpitface exterior block and rigid a bad idea?
  • If I insulate the interior foundation walls, and DON"T insulate the exterior walls, will this create moisture issues within the block foundation?
One last detail:

  • Along the top edge of the block wall, is 12" tall row of brick. After pressure washing some of the original parging off, I noticed that the brick was spalled in places. I am not sure how to take this into account when choosing the mortar and parging material.
In general--whether for this application or others-- is it safe to "default" to a lime based system for both mortar and parging?

Please advise. thank you, Jeffrey
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Before going to far have you had any discusion with your insurance company you have your flood insurance with?
Just second hand info but there's been people on this site chating about now having to pay an outragest amount for insurance or get rid of the basement.
Insurance companies will do what they do.
The basement will no longer be a basement in the way it used to be.
If they increase rates across the board which is expected to happen, I will deal with that then.

In the future, tt will be used as a studio.
All of the utilties--heating system, DHW, etc have been relocated to upper levels.
The goal is to have zero organic materials or utilities in the basement.

basically it will be a basement with polished floor and concrete walls. lighting and electrical will run through floor joists.
Because the ceiling height in the basement is 6'6", it would have to take another 12 foot storm surge--what the army corps of engineers is deeming a 250 year storm--to make it above basement level again.
But we are rebuilding as if it will happen tomorrow.

best, J
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My suggestion is to use Thoroseal (cement-based coating) and not a paint/sealer since it becomes a part of the concrete in the walls. Do a light pressure wash to remove dirt and loose particles. Follow the Thoroseal mixing (especially timing to allow "fattening" before final water). Mist the walls with a garden sprayer when necessary to maintain a moist (not dripping wet) surface just prior to the application. A bond enhancer/latex may be used. The mix will be as sloppy as pancake batter and should be applied with a large brush (whitewash?) and can be a little rough. A second coat may be applied within the suggested time frame (24 hours?) to make everything prettier and can even be painted/coated.

The result is concrete surface that is more water resistant, but is not a vapor barrier and can accept almost any type of surface you choose depending on your selected systems. It is a sloppy, messy process, but it works well and has been used for architectural and sculptured rehabs and I have specified it on some old dam restorations to create a good surface.

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