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Re: Wood trusses over pool

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Since you're the engineer on the scene you have the best handle on the conditions. 

I believe all the hand wringing about decay, shoring, corrosion are a little overdone & definitely  premature.

You did say it was a new long in service?

To answer your initial question
>>>Does anyone know of a supplier of small analog barometer devices that I can use to monitor the humidity in the attic and building?<<<<

I have used them a lot for all sorts of instrumentation & transducers.

They have a wide range (cost & performance) of hydrometers. The recording type would be great for establsihing a record.  But thye

To answer your second question about a "post installed" vapor retarder........I assume you want something to go onto the GWB, behind it?

Here is an awesome product I discovered ~20 years ago.   I would suggest you research it with the tech experts at Rustoleum.

a two coat application will get you down into the .5 perm range (or better)

But............. GWB is not a great substrate.   :(

IMO (if you get the ok from Rustoleum), used in conjuction with proper ventilation you might be able to get by without removing & replacing the ceiling

Since your talking about a large area, a test section would definitely be in order

But regular GWB over a pool doesn't sound like a good idea.


On 3/9/07, Christopher Banbury <cbanbury(--nospam--at)> wrote:

I am monitoring the humidity in the attic space over the next couple of weeks to see if I can document the elevated humidity levels. As I mentioned earlier, the building is newly in service and this issue does not pose a safety concern at this early stage.


There are no wall or floor cracks, only a separation of the gypsum board ceiling at the perimeter wall and a ceiling crack along one of the hip girders.


I will review the trusses for deflection issues as part of my assessment, however, since the trusses have been lightly and statically loaded while the cracking is occurring I'm not inclined to suspect design deflection issues.


For retrofit considerations I am wondering if there are any suggestions as to how to vapor-proof the ceiling. The trusses are not treated and will not endure wet service conditions.



Christopher Banbury, PE


Ark Engineering, Inc.

PO Box 10129 , Brooksville, FL 34603

22 N. Broad ST , Brooksville, FL 34601

Phone: (352) 754-2424

FAX: (352) 754-2412


From: Richard Phillips [mailto:Rjohnsonphillips(--nospam--at)]
Sent: Friday, March 09, 2007 4:31 PM
To: Christopher Banbury
Cc: seaint(--nospam--at)
Subject: Wood trusses over pool


Mr Banbury:  From what you have described you have a potentially dangerous condition.

Enclosed spaces above pools can develop 95 % humidity, which can cause dry-rotting of untreated wood.  The ceiling distress you describe is probably excessive deflection of the wooden support system.  I suggest that you shore the trusses and then carefully inspect the wood bottom chords for fungal decay (dry-rot).


Dick Phillips CE SE FSEAOC