Building mold contamination resulting from the extinguishment of a building fire:

This article discusses how fire damage and mold damage might be recognized in a building and how we might distinguish between black stains and white sealant paints used in both fire damage repair and mold remediation projects.

Post-Building Fire Mold Contamination

Mold contamination can follow a building fire and may occur in building cavities nowhere near where the fire itself occurred.

Here we explain when, where, how and why a building may becomemold contaminated following a building fire as water from fire extinguishment (or from a building left open to the weather) travels through building cavities.

[Click to enlarge any image]

Reader question: I found your website and found it extremely helpful. However I have a very particular situation and would like to have your suggestions and comments. Here are the series of facts leading to this e-mail to you.

Type of house: 1983 Canadian style with drooping front roof purchased January 2011

Information from seller: 2006 inside renovations (kitchen, living room and bathroom) 2008 new roof – completely redone. When asked if there had ever been water damage, problems or fires in the past the seller answered no to all questions.

Recent leak history: March 2011 – lots of snow and then + 5 degrees Celsius- our roof started leaking and water was leaking in our front door frame.

We went up in the attack and discovered that the air system did not have the protection to prevent fine snow to enter the roof area. There was a line of snow in the middle which probably melted.

After discovering this, I decided to have an engineer who work in construction problems, etc.

3rd April 2011 – Engineer visits and says there is an air problem in the roof top and all the wood seems to have been painted over and there seems to be dark black marks under the paint.

He also says the front part of the drooping roof does not have sufficient space to let air circulate and that this probably caused the water to run down the door frame inside. We are still waiting for the official report.

9th April 2011 – The seller informed us that there was a fire at the construction stage of the house 28 years ago and that is what the black is all about in the roof...They painted over it to seal in the smell.

So we have two different diagnoses of these black and painted areas: mold or fire. What do I do now?

1. How can I check if I actually have a mold problem ?
2. How do I fix the black fire appearance or mold traces in my attic ?
3. How can I fix the insulation problem in my roof (cathedral part of the roof ? - C. & R.

Reply:

A competent onsite inspection by an expert - a real one who knows both mold and fire damage - usually finds additional clues that help accurately diagnose a problem.

Also your photos are less than one one thousandth of what I'd look at if I were inspecting the building, so any opinion I give is of necessity incomplete.

Photo: mold growth on water-damaged plywood subflooring.

That said, here are some things to consider:

• By your account the seller was not forthcoming about the prior fire.
  
  However if proper inspection, assessment and repairs were made, the house may not be facing a costly fire-damage repair at all. Nevertheless, there might be some residual impact on the property value at re-sale time.
• It is common practice to paint over fire damaged wood provided the wood is not structurally compromised - to seal in odors. Painting over fire blackened wood is not harmful.
• It is possible to distinguish between mold and fire damage:
  
  A careful inspection of the painted areas and the surrounding material can often sort out the difference between fire-damaged surfaces that were painted and mold-contaminated surfaces that were coated, as I elaborate below.
• Fires do create a secondary mold risk at a property:
  
  extinguishing a fire, presuming it was extinguished with water, dumps a lot of water into and through the structure. That process, when the fire is in the upper part of the structure in particular, sends a lot of water through lower ceilings and walls. Unless all of those areas are opened, gutted, dried, a future mold problem in those areas is a high risk.

• Your photo of blocked soffits and where no white paint appears (photo at left) and no black marks on sheathing also shows a sister rafter at the right side of the photo - possibly part of a post-fire roof repair/replacement, or sometimes this is done to straighten a sagging roof.
• This photo shows the soffit virtually blocked, black stained fiberglass insulation in the eaves in a pattern that could be due to air movement/air leaks, and thermal tracking. The engineer is correct that roof venting is improper and blocked, risking a moisture and mold problem.

• Your next two photos (below) how white-painted surfaces low at the house eaves on sheathing and some rafters, more sistered rafters, Some of the roof sheathing appears to be plank or T&G boards, other, plywood.
  
  In the photo showing a white-painted sistered rafter under roof sheathing and diagonal bracing (below-right, looks much like a repaired truss),
  
  the paint pattern on the upper truss chord and
  
  the absence of paint and absence of mold on the roof planks that rest atop the sistered/repaired roof truss
  
  form a compelling argument that the paint was applied relating to a fire not mold - mold wouldn't grow on just the truss side and not on the adjoining wood roof decking.
  
  An exception would be if the roof decking was replaced and the old, repaired truss left in place. Usually plank roof decking is older than plywood roof decking.

• Your last photo shows insulation pulled back and what looks like blackened ceiling, studs, and sheathing.
  
  I cannot tell from the photo where in the structure this is, if it is in a moisture path, if there is corroborating indication of surrounding moisture staining on insulation, rusted nails, etc. or if it is left-over charring from the fire.

Given that the (apparently) vertical wall in this last photo is black with something, an astute home inspector who had access to this area during a pre-purchase home inspection would be expected to observe and comment on that anomaly and to warn you of its possible consequences.

Suggestions for Handling Mold & Fire Traces in a Home

Our photo (left) illustrates extensive fire damage to a home at which the fire originated in a (probably creosote laden) metal chimney venting an overheated woodstove, spread to the building's roof and burned back down the building's wall.

A combination of weather conditions and speed with which demolition and repairs began seemed to avoid a concern for mold contamination associated with water used to extinguish this fire.

1. How can I check if I actually have a mold problem in this house ? 
   
   An inspection by a expert who is familiar with mold contamination should include a look at the history of the extent of demolition and repair after the fire as well as looking carefully at the water path through the building.
   
   In addition to visual inspection for mold or mold-suspect materials, it makes sense to sample some surface areas especially ones where your engineer thinks that there is a mold problem .
   
   Surface sampling is in order; if you like you can also screen the building for mold using air and dust sampling but the visual inspection and surface samples are most important.
   
   Start by reading MOLD / ENVIRONMENTAL EXPERT, HIRE ?, and for further details on inspecting a building for mold
   
   see MOLD DETECTION & INSPECTION GUIDE
2. How do I fix the black fire appearance or mold traces in my attic ? 
   
   Use sealant paints that are approved for fire restoration to cover or paint over unsightly fire blackened members, presuming that an expert has assured you that no further structural repairs are needed.
   
   Don't paint over mold: moldy surfaces and materials should be physically cleaned. If you want to use a fungicidal sealant afterwards, that's fine.
   
   See ACTION GUIDE - WHAT TO DO ABOUT INDOOR MOLD
   
   and see MOLD SANITIZER, SPRAY, BIOCIDE USE GUIDE
3. How can I fix the insulation problem in my roof (cathedral part of the roof ?
   
   Attic ventilation, to work effectively, needs continuous air intake at the eaves and outlet at the ridge. Insulation & ventilation contractors use baffles to provide an air path in through vented soffits and add a ridge vent.
   
   See our article series on attic ventilation beginning at ROOF VENTILATION SPECIFICATIONS

...

Continue reading at FIRE DAMAGE vs MOLD DAMAGE or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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