Weeks 19-25 The Moisture Saga

26 03 2012

It’s been one month since the last post, which was spent trying to determine the cause of the moisture problem in our new vaulted ceiling.  After the roofing company repaired the top section of water damaged plywood and felt, our architect suggested doing a condensation test before closing up the ceiling with drywall.  The architect had the contractor cover the open ceiling with plastic and said to watch if any moisture forms.

Well guess what, by the next afternoon the top side of the plastic facing the ceiling was dewy and even a few water droplets had formed and dripped onto the plastic.  It was like a sauna in each joist bay in the peak of the vaulted ceiling and this went on for a few days.  Science Experiment 1 ends, but we clearly still had a moisture problem.  

The architect concludes there is still moisture present in the rest of the framing, drywall and insulation, so he suggests removing a 1-2 foot section of ceiling drywall where it meets the top of the 2 side walls.

When the contractor opened these sections some of the insulation he removed was damp.  Not like the saturation levels found in the peak, but still some moist spots.  So I got out my trusty moisture meter and took as many readings as possible on the remaining sections of drywall and all the exposed framing.  The most moisture was around the recessed light fixtures.  Overall the lower 2′ ceiling section didn’t have nearly as much moisture as the top 2′ section. We let it dry out for a few days before starting Science Experiment #2.  In the meantime, we tried to figure out how best to proceed.  At this point our architect and contractor believed it was a roof leak and once the water got into the room it was unable to evaporate, because there is no ventilation in this vaulted section of the roof.  So what are our options?


We asked why aren’t there any vents in this vaulted ceiling and whether some can be added.  The architect claims that he has built many homes with vaulted ceilings this way (without any eave or roof/ridge venting), because Los Angeles is a desert and not very humid.  Separately our contractor said his house has a vaulted ceiling with no venting and he hasn’t had a moisture problem.  The architect offers an alternate design dropping the ceiling to create a small attic space that is open to the roof vents in the adjoining attic.

Uncertain what to do, we researched the topic on the internet and talked to other professionals including another contractor, a city inspector and a couple of other architects.   This contractor came to the house and noticed the lack of vents, but said only once did he see a condensation problem in a vaulted ceiling in Los Angeles and that house was located at the bottom of a canyon where moist air tends to settle.  I spoke to a city inspector on the phone, but he said it had to have been a roof leak as he has never heard of a condensation problem in a vaulted ceiling in this part of the country.  The local architect who reviewed our city approved plans and examine the addition said that the unvented bedroom ceiling does not meet minimum building code in our area, nor does the crawlspace ventilation.   Oh great,  another problem crops up.

So I go to test moisture levels in the subfloor, but when I turn over one of several loose sections of plywood I discover … the dreaded M-word … Mold … growing on the underside of this plywood.  I got a sick feeling in the pit of my stomach.  I go into the crawlspace and remove the fiberglass insulation in an adjacent floor joist and see the blackish spots there too and surmise it’s likely under the entire subfloor.  Ugh.

A bit of history … the contractor had left 3 openings in the subfloor, so the bedroom was open to the dirt crawlspace.  These openings were cutout of the floor several months ago, because the contractor had to remove several water damaged, rippled sections of plywood, the result of several rainstorms before the roof was added.  At that time we had asked the contractor to cover the partially framed structure, but he said in his experience it’s not necessary to cover it as the wood will dry quickly.  We were skeptical and pushed, but he insisted so we dropped it.  Just to be on the safe side during and after each rain we removed any standing water with a wet/dry shop vac and a push broom to help the plywood floor dry faster.  But there were still numerous heavily rippled sections of subfloor, which were then cut out but left open.  It wasn’t until I noticed the yellow spot and moisture in the ceiling that I asked to have these floor openings covered, because I thought about mold getting into the room because it exists naturally in our air especially in dirt crawlspaces under a house.  Could this be the source of moisture in the ceiling?

Well now we’re wondering if there wasn’t enough time for all the framing and flooring to dryout especially with the insufficient venting in the crawlspace and roof.  At the very least it couldn’t have been good to have the dank air from the dirt crawlspace freely flowing up into the addition especially the unvented vaulted bedroom.  [Please post a comment if you’ve had any similar experience or knowledge of this situation.]

I emailed the contractor and architect about the latest discovery of mold in the subfloor and relayed the information from the other architect about the roof and crawlspace ventilation not meeting minimum building code of 1 sf of venting per 150 sf.  And that the grading is too high along the back corner of the addition.   The contractor quickly conferred with the architect and determined that all they needed to do to meet code was to open a crawlspace opening in the foundation and lower the ceiling as mentioned previously so there is about a foot of attic space above the bedroom with access to the existing roof vents in the adjacent section of the addition.

This convinced us to forget about having a vaulted ceiling,  which when properly constructed to handle extreme swings in temperature require complex and costly ventilation methods, neither of which we felt was worth it.  We just didn’t want to take a chance of there being any moisture problems in the future. The contractor quickly resolved the crawlspace ventilation issue by cutting an opening through the foundation wall and lowered the soil grade around the back of the bedroom addition where it was too high.  [Note:  At the beginning of the project I asked if that crawlspace opening could be eliminated because it would be in the way of the walkway. The contractor said he checked with the architect and city plan check and both confirmed it wasn’t necessary, thinking only about the building code of being within 20′ of the bathroom and forgot about the ventilation code.]

Clearly the lack of ventilation in the subfloor led to the mold growth, but it’s unclear what caused the moisture in the roof/ceiling.  Was it a roof leak that couldn’t dry out, because there was no ventilation or was there another source of moisture that led to the condensation at the peak due to daily temperature swings?  The ground under the floor is bone dry. One theory is that while the addition was being framed it rained a number of times before the roof went on and there was standing water on the subfloor, which rippled up in several places.   Perhaps the lack of adequate venting in the foundation prevented the floor sheathing from completely drying out before the floor insulation was installed, which trapped the moisture against the plywood.

I took humidity readings in the crawlspace for several days and found it to hover around 75%, which is high compared to the 55% humidity in the existing crawlspace.   At the same time the humidity levels in the peak would soar to 95% during the hottest part of the afternoon.   Is it just the environment in this area?  We may never know the source(s) of moisture, but now that the ventilation was increased in the crawlspace the humidity hovers around 55% like the existing crawlspace. Anyway I got estimates from a couple of mold remediation companies.  Then last Thursday and Friday a mold remediation company came to grind, scrub, wipe, and seal the ceiling, subfloor and framing, which the contractor agreed to pay for.  So now it seems like we’re finally going to be able to move forward again on the addition, which is nearly 2 months over schedule.

Here are some photos of this ongoing moisture saga.

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