Latest Discussions : Basement & Foundation

doug seibert

10:48AM | 01/25/05
Member Since: 08/10/02
842 lifetime posts
Do you have combustion heat ?

A poorly vented furnace can deposit soot in the air........and it settles on the slight condensation over the cold studs in the exterior wall..........


05:01PM | 01/31/05
Member Since: 01/30/05
360 lifetime posts
Although Doug could be right (regards to condensation and dust/soot from forced air heat (heating oil fuel or natural gas), more likely you have a two-fold problem, namely condensation AND mold/mildew.

Cool air, or just the cold from the outside wall and poor insulation can allow for the cold to be transmitted via the framing elements of these walls. Condensation being "wicked" through the wood framing, through the drywall/drywall; and, as most dry wall is "taped" with paper tape or fiberglass with an adhesive, then "mudded" smooth (dry wall or "spackle compound" the seams and over the nail heads (in pairs) or screws, and that same moisture is being "wicked" via the nails/screws and they are "popping".

The black streaks may be dirt/dust/soot colecting on the condensation/cold areas or it could be mildew or MOLD growing on these condensation (wet)/cold spots, or a combination of two or three of these elements.

Unfortunately that you have these "black streaks" on walls that carry from exterior walls, and on exterior walls, but not interior walls, indicates that you may have a MOLD and/or mildew problem, and that these exterior walls are not properly waterproofed (perhaps just damp proofed), nor insulated properly.

Unfortunately prime temperature environment for various mold and mildew colonies is oftentimes between 35 and 110 F.

There are some types of mold (black, but some times other colors) that are extremely toxic to humans and pets, although there are just as many that are mostly benign.

IF you have toxic mold, or a less dangerous mold or mildew problem, you may have a situation where the lumber framing is contaminated and has been growing for a while and is just now reaching through the paper edging on your "dry wall" or "drywall". If that is the case, surface cleaning of the drywall situation will not stop the problem.

I would recommend that you investigate the following:

1. If its "soot" it won't brush off easily, and would need warm water with a surfactant (like detergent) to remove most easily.

2. If its mold/mildew to remove, might wipe away with warm water (then reappear a few hours/days/weeks later) or require a bleach and water solution with a few drops of dish liquid (like dawn - but NOT antibacterial) to remove. 2 ounces regular clorox bleach and 19 ounces water plus 2 drops Dawn, Palmolive, or other liquid dish detergent (not dishWASHER detergent).

Until you solve the question of the origin of the problem (COLD/condensation) (air leak, insulation, waterproofed foundation, etc.) then correct and repair accordingly, this will be a continuing problem each cool weather season, and if you have a mold/mildew problem, you will need to take corrective action. Before dealing with a suspected mold/mildew contamination situation, would advise consulting with an environmental engineer expert and getting samples tested at an accredited laboratory (check with your local EPA for a list of accedited labs), and if you have toxic mold, hire professionals to correct the problem, as cross contamination is quite easy and the toxic molds are major health hazards.

Good luck.


02:55AM | 02/01/05
Member Since: 01/05/05
83 lifetime posts
What is on the house for siding? What part of the country do you live in?


09:31AM | 02/01/05
Member Since: 01/24/05
3 lifetime posts
Thanks for all the input. Here is some additional info about the house

1. The house is in Northern California, SF Bay Area in San Jose.

2. The siding is stucco and walls are insulated

This is the first time I'm noticing this problem.

Last 2 months we used the fireplace about 8 times and we burned Java logs -- these are made out of recycled coffee grinds. The walls showing this problem are close to the fireplace. We also burn incense sticks daily in the kitchen, close to the area where the problem is being reported.

The house is heated with a gas furnace with ducts in the crawl space.

I have lived in the house for 12 years and this is the first occurrance of the problem.



09:35AM | 02/01/05
Member Since: 01/05/05
83 lifetime posts
You might have solved your own problem!

doug seibert

11:35AM | 02/01/05
Member Since: 08/10/02
842 lifetime posts


09:50AM | 11/30/05
Member Since: 11/29/05
3 lifetime posts
I have just encountered this problem on one of my rental houses. Description is identical to what I am seeing. Would appreciate an update as to what caused the problem and how was it solved. Thank you!


doug seibert

01:59AM | 12/01/05
Member Since: 08/10/02
842 lifetime posts
If you BURN gas or oil to heat the house or HotWater.....Have the appiances checked for combustion efficiency, check the flue and available "make-up air".......the by-products of combustion, if not properly vented, condense on the cooler portions of the wall causing the "shadowing".....(an uninsulated wall tends to be cooler between the studs.....thus the X-ray pattern).......You can be poisoning your tenants with Carbon Monoxide.....

Unvented heaters.....kerosene heaters.....firelogs.....candles...... all contribute "soot" and gases into the home....

Get a CO detector.........


02:19AM | 12/01/05
Member Since: 11/29/05
3 lifetime posts
Thanks Doug:

I am more concerned about the possibility of mold or mildew. The house has a heat pump, but has propane for cooking and gas logs. The gas logs could be the source of the black stains. A CO detector is a good idea.

This is the first time we've seen this in the two years we've owned the house.

How would I check for mold or mildew other than removing the drywall?


doug seibert

03:30AM | 12/01/05
Member Since: 08/10/02
842 lifetime posts
I'm no expert on mold........But you need a source of moisture to encourage the growth of mold/mildew.......So, do you have an obvious water problem in the house ? The molds and mildews I have seen follow a predictable pattern radiating from the source of water/moisture........they don't necessarily stop and start along the same wall "shadowing" the studs.....( the OriginalPoster had shadows that followed the wall studs location )......What exactly is the evidence in your house........

If you have a water intrusion/mold problem then the Federal govt has reports and proceedures and tests for mold remediation......and there are plenty of companies ready to Help........but IMO.....I think the private sector mold "testing" is rampant with "salesmen"......a solution waiting for a situation.......

If those logs are the UNvented variety I would take a serious "reality" check.....and how are you making the hot water ?

Sorry re:missing/broken link.....the posted link above was named "sampling stains for fun and profit" appears it is no longer at that gov't website.......


06:14AM | 12/01/05
Member Since: 11/29/05
3 lifetime posts
Shadows are only on the studs. Gas log heater in unvented. Crawl space is moist, but no standing water. Any other info needed, please let me know.




12:48PM | 06/25/15
Unexplained Stains there is dark stain on ceiling the shape of the rafter on all the Cathedral ceilings. anyone have seen this before and what the cause. I appreciate any input


05:53PM | 02/16/18
Does propane heat cause yellowing in my house ?


12:20PM | 06/11/18
new lighting all the cuts and new drywall are dark all drywall screws everywhere we Speckled, some sort of dust everywhere else can candles and burning incense cause something like this


07:17AM | 04/18/19
Candles and burning incense can cause black soot like substance to appear on walls etc. and not sure bout the yellowish color. Hope that helps somewhat.

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