Basement efflorescence (no flooding)— If / how to address prior to finishing
Hi,
I have an unfinished basement in my 1960s home where one wall has clear evidence of efflorescence (picture). We have not had any visible water entry into the basement beyond this for many years, despite many heavy rains.
I’d like to finish the basement using one of those basement wall systems (Basement-to-Beautiful Wall Panel) which seems to be good for avoiding mold and the like since it includes rigid foam insulation.
Would it be necessary to create an drain system to deal with effervescence ahead of attempting to finish the walls or would that be overkill given the no flooding? If so, I’d have a preference for internal over external as digging up my back yard would be problematic (limited access due to fencing / terrain)
Thanks.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Not a pro but have had same issues in 3 NE basements. IMHO, Efflorescence comes from moisture migration thru wall and evaporation at the inner wall face, leaving behind dissolved salts. There are options on how to deal with the mechanism, pro's and cons' of each.
One basement I bought had been conventionally finished with studs and fiberglass, PE vapor barrier unsealed on cold side of wall = condensation, mold, and the Pergo floor and bottom of wall rotted. Don't do that.
One had enough moisture migration over a long enough period of time that the inner face of the CMU's was literally falling apart ie. a dust pan full of sand and dust could be swept up from 20 ft of wall every 6 months, 1/4" of inner face of blocks was missing after 70 years ie. the moisture migration needed to be addressed either at source (excavation and exterior sealing, grading, etc) or, perhaps, by eliminating the evaporation at the inner face and just let the concrete wall be wet. 2/3 of the basement was finished, again not sealed and with loose sheet of poly hanging on cold side of wall. Again moisture condensation behind poly sheet, black mold everywhere. Same mistakes repeated in multiple houses ... aggravating.
Might be at risk of mold behind those nice panels you pointed out and possibly moisture issue at mud sill. I used closed cell spray foam on 1st and 3rd basements, 2-3", to eliminate moisture migration via stopping evaporation, insulate, air seal esp rim joists, all in one solution. Good overhangs, cedar siding, no basement leaks and only minor localized efflorescence in 3rd basement, I'll deal with exterior grading as source; with drying to exterior, not worried about mud sills.
Those panels look really nice. but I'd want to think about perimeter sealing + in between gaps 100% sealed to block bi-directional vapor migration.
In the first house with the condensation and rot, there was water getting into CMU wall from an uphill slope and poor construction, i.e. the blocks were level full of water 2-3 ft high on the upslope side -->> we did have to put in an interior perimeter French drain to a sump pump, drill the CMU's at base, put up dimple mat 3' high around perimeter, and then we sprayed closed cell over that to seal it all.
I guess I'd price closed cell + basic stud wall on treated plates vs your panels + finishing system. Closed cell can be installed for $1.50 / board ft around here, and the conventional construction after made it kind of an easy decision for me. Worked out to about $40 / linear foot of 8' basement wall to do 2-3" from top of rim joist to about 3' deep, then 2" down wall to slab.
If the basement has remained dry for a long time, it’s possible that the issue with bulk water was corrected at some time in the past, by a previous owner (assuming here that yon bought the home relatively recently). If that’s the case, you can just deal with the efflorescence and not worry about drainage. If you do need to deal with the bulk water issue, that’s best done on the exterior grading the ground so that it slopes away from the house, adding gutters if you don’t correctly have any, and possibly also adding a drainage system to carry runoff away. Adding drainage on the interior is not ideal, but is still doable. In interior systems, I often use a simple mat against the wall to create a drainage plane, then use a perimeter drain in the floor underneath. You can then build a wall various ways over the dimple mat.
The drylok people make a cleaner to deal with the efflorescence. If you have a lot of the crusty stuff on the walls, I’d scrape the bulk of it off mechanically prior to using the cleaner.
Bill