Mezzanine Void Project: Addressing Termite Infestation and Damage

ABOVE THE MEZZANINE ceiling is a large void that, until last week, was inaccessible to human beings — but accessible to termites. 

(Previously termites had been spotted through a ceiling hole in the southwest corner of this space, and also in its northeast corner through a roof hole, so the likelihood seemed very high that they were established also in the void between.)

Back (western) wall of the sanctuary.
(As usual, click/tap on an image to enlarge it.)

This post describes how we created access for humans — who observed not only the purported termite infestations within, but also the structural damage that they have caused.…

Executive Summary

We had an access hole cut into the ceiling of the mezzanine. Then a termite inspector and a structural engineer went inside the void above the ceiling. They report that infestations are widespread within the void, and the termites have seriously damaged two roof rafters and two smaller portions of structural wood. Treatment and repair work are warranted. We are awaiting a quote for both.

Phase I:  Gaining Access to the Space

The space spans the mezzanine ceiling. It is bounded above by the western edge of the barrel roof, which slopes down to a flat roofline at the front of the building. It is about 6 ft. tall at its highest point (its eastern edge, at the center of the barrel). 

Last week, while a contractor was already on the premises to cut test holes in the south wall (see HERE), they also created an access opening to this void. 

(The mezzanine ceiling was recently tested for asbestos, and none was detected.) Beforehand, to prepare for the cutting, Ruben and I draped plastic drop-cloths, to make a curtain to contain the plaster and wood dust.

The contractor cut the opening near the eastern (highest) side of the void, and near the center of the room = tallest part of the barrel roof.

The rectangular opening is between the 16”-spaced joists, about 30” long. The contractor also cut a piece of drywall to size, which is now screwed into the joists, as a temporary cover.

Because we had this task done together with other similar work on the premises, the out-of-pocket cost was quite nominal, about $300 (including drop-cloths and tape).

Phase II:  Inspecting the Space

Both a termite inspector and a structural engineer went inside the void above the ceiling. They reported that infestations are widespread within the void, and the termites have seriously damaged two roof rafters and two smaller portions of structural wood. 

Evidence of infestation

Evidence of damage

Treatment options

Treatment work is now warranted; otherwise, the termites will keep on doing damage, out of our ready reach. Although we are awaiting a formal report from the termite co., the inspector said that he would recommend spraying all surfaces of the void with Tim-bor liquid (a borate solution). 

According to lab tests sponsored in 2009 by the State of California, Tim-bor liquid is best for long-term preventative treatment. In other words, it would keep existing infestations from spreading into new areas within the void: “Drywood termites did not feed on … Tim-bor … treated surfaces.” 

That’s indeed important in a space that is not regularly inspected! At the same time, Tim-bor is not very effective in killing existing infestations, because it kills only on contact; termites do not pass it along to others. (“Liquid borate deposits become crystalline and adhere tightly to the surface to which they are applied.”)

In other words, it would seem worthwhile to have the obviously infested areas treated initially with another product that is known to be highly effective for localized treatment, such as Termidor 0.06%. Then spraying with Tim-bor could be done 4 weeks later — after the Termidor has had an opportunity to kill back the existing infestations.

Maybe one of those steps or the other can be done at the same time as the structural wood is reinforced. Of course we would want the new wood to be sprayed with Tim-bor.

Repair options

Repair work is now warranted, for the integrity of the roof is compromised. Although we are awaiting a formal report (and price quote) from the termite co., the inspector did tell me that he would recommend reinforcing (“sistering”) two rafters that run east-to-west, as well as reinforcing shorter stretches of structural wood in two other places. 

The structural engineer agreed with that assessment and recommendation, except that he believed that the shorter pieces should be replaced rather than merely reinforced.

Retaining access to the space

We need to decide whether this space should now be annually inspected and treated for termites. The current opening configuration is not designed for regular access. That would require some additional carpentry work, to make a removable panel and a frame to house it. 

However, rather than spend money on that approach, I am more inclined to consider this void to be an area that gets inspected only every two decades or so (in the absence of fumigation). That is, the access panel would basically get sealed but its location would be marked, to enable future access.