August 19, 2023
The issue of paint blistering off of Yucatan walls has recently come up about 7 times in various local expat FB groups, where people new to Yucatan are very worried about patches of paint coming off damp spots in Yucatecan walls … Please see the technical-scientific explanations below about: “salitre”, efflorescence & “rising-damp” below, lower down in this report.
The issue of paint blistering off of Yucatan walls has recently come up about 7 times in various local expat FB groups, where people new to Yucatan are very worried about patches of paint coming off damp spots in Yucatecan walls … Please see the technical-scientific explanations below about: “salitre”, efflorescence & “rising-damp” below, lower down in this report.
… The recent posts on MINOR humidity-moisture damaged walls, have been accompanied by a few overly-excited commentors mistakenly imagining that our VERY COMMON problem of “salitre”, efflorescence, “rising-damp” is somehow, supposedly the “black mold” that’s found in the USA & Canada.
This raises a Common Question:
How do you tell the difference between USA’s toxic Stachybotrys Chartarum black mold versus all the other basically-harmless** black molds?
Answer: Look at a map.
If you are in Yucatan … it’s not toxic Stachybotrys Chartarum … 🙂
If the map says you are in the USA or Canada, then GET IT TESTED. 🙁
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Black Mold Scientific Facts:
The most common black mold is Cladosporium, which has NO known toxic side effects. This type of mold is common both inside and outside of homes and it is generally harmless.**
Other HARMLESS** black molds include Alternaria, Aureobasidium, Dresclera, Pithomyces, Stemphylium, and Ulocladium, but are generally harmless* because THEY DO NOT PRODUCE MYCOTOXINS.
Still … NONE of these are toxic molds that produce mycotoxins,
It’s the ~nasty USA’s~ nasty-Canada’s~ one (1) single species of toxic mold … Stachybotrys Chartarum … that produces nasty mycotoxins.
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**Heavy or frequent exposures to generally harmless black molds can however trigger allergy~asthma symptoms in people who have allergies.
“Harmless” => No mycotoxins produced.
Example … Up in the USA & Canada Alternaria, Alternaria molds are the ones that commonly cause severe allergy symptoms. …
Alternaria has that distinctive “dank basement smell” or “musty old book stink … that are so common across the Midwestern & Northern USA, and Canada.
Fortunately, Yucatecan homes RARELY have Alternaria mold, unless someone brought a bunch of old moldy Canadian books, or old moldy-USA books down here.
Dr. Steven M. Fry
Ph.D. in Environmental & Public Health, and Chemistry
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Why write about this?
It really is important to reassure new expats’ unnecessary worries.
Why would some new expats worry?
… Unfortunately, two different well-meaning USA-contractors, seeing fotos of normal ordinary common “salitre”, efflorescence, “rising damp” moisture that ruins some paint … got alarmed, and went on to falsely claim:
… Unfortunately, two different well-meaning USA-contractors, seeing fotos of normal ordinary common “salitre”, efflorescence, “rising damp” moisture that ruins some paint … got alarmed, and went on to falsely claim:
“Cut your losses and move. “
along with their very-mistaken claim:
“Mold is (supposedly) a killer and not to be meddled with. I couldn’t ever overstate that enough.“
. . .
Sadly, these claims are panic-driven, gross overstatements, that fit the USA … but do NOT fit Yucatan at all.
Notice that while the USA has HUGE problems with Stachybotrys Chartarum, the ONE single species of black-mold that is toxic,
… meanwhile, YUCATAN DOES NOT HAVE TOXIC BLACK MOLD …
. . .
Seriously, US & Canadian builders & tradesmen know USA & Canada, but they so often really don’t know Mexico & especially not Yucatan. 🙁
THERE ARE NO HEALTH REASONS for people with to “sell their home” due to common paint issues,
especially for Yucatecan homes that have normal blotchy sections of paint pushing off by salts leaching out of the concrete… because there really are no health reasons at all for almost all people**.
especially for Yucatecan homes that have normal blotchy sections of paint pushing off by salts leaching out of the concrete… because there really are no health reasons at all for almost all people**.
As a Dr. of Public Health, I (and others) have monitored over 30 yrs of test results for toxic Stachybotrys Chartarum black mold here in Yucatan, and
there HAVE BEEN NO POSITIVE TESTS in 30 yrs – No evidence at all of Stachybotrys Chartarum here, …
even though Stachybotrys Chartarum has been a HUGE problem in the USA & Canada. 🙁
Dr. Steven M. Fry
.
.
= = = =
Finally:
“Salitre” ~ Efflorescence ~ “Rising Damp” Issues here,
… that commonly push off the paint in big blotchy areas of Yucatecan walls, esp. down in the first meter of the wall, next to the floor:
The issue of “Salitre” ~ Efflorescence ~ “Rising Damp” … is super common here.
Why?? … When walls are built with no moisture barrier between the wall and the concrete foundation, realize that most of the concrete here is likely poured right on the damp-wet bedrock.
Why?? … When walls are built with no moisture barrier between the wall and the concrete foundation, realize that most of the concrete here is likely poured right on the damp-wet bedrock.
Concrete is just like a sponge – it wicks water-moisture up from the damp underlying bedrock, into our walls (when there is no moisture barrier installed). … The moisture then dissolves salts in the concrete, and as the salt-laden moisture wicks out to the surface to dry, and carries the salts with it. … The salts then push off the paint & weaken the concrete in that area…. Here it’s called salitre … in England => rising damp … in the US & Candian construction trades it’s called efflorescence.
If you have this issue in your home, you need a decent experienced albañile to chip-out, chisel*out the soft, salt laden material, down to the underlying solid rock … and then he’ll chemically treat that underlying rock to get the new replacement concrete to stick (typically acido muriatico followed by dilute bleach). … A good albiñile will next also add special additives to the concrete that they patch with, to get the new concrete to bind to the rock, and to not transmit so much humidity.
. . . .
A different approach is to chip out all the soft material, down to the solid material – with a nice straight border cut by a diamond saw … in about a 4 inch high strip above the floor … and leave the rocks exposed, for the moisture rising from the foundation & floor to just evaporate out into the room.
And yes, this bare-border approach is approved by INAH for homes in Merida’s “historic Centro district”.
Good luck … and stay calm,
Dr. Steve
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For final emphasis: Here’s an example of salitre~efflorescence that looks pretty scary … but the black mold here IS NOT TOXIC … just annoying. 😦
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Feel free to copy while giving proper attribution: YucaLandia/Surviving Yucatan.
© Steven M. Fry
Read-on MacDuff . . .
Surviving Yucatan 
Thanks for this info. I’d thought it was all toxic.
Fortunately, the opposite is true.
Only the one species of mold ( Stachybotrys Chartarum ) makes the mycotoxins … yet, that’s the TOXIC Black mold that USA & Canada have
… while Yucatan has only basically-harmless species that produce NO mycotoxins.
Cheers
Dr. Steven M. Fry