Compiled by Carolyn Siegel, 10/16/05
1. Don't know about problem spreading. We replaced a few sections like this with plywood, painted over. Hardly noticeable and cheaper than celotex.
2. The main thing to be concerned about is the celotex panels can hold water against the roof beams and 2x4s that make up the walls and cause them to rot. 4 years ago I investigated replacing several bad panels. There was a place in Menlo Park that still sold them (can't remember the name of the place). They were something like $80 for a 2 ft by 8 ft piece and was a slightly different color in appearance. In the end we decided to replace all of the celotex panels with tongue and groove wood. In doing so we discovered 12 rotting beams that needed to be replaced.
At the very least you need to patch the roof to prevent more water from getting in (which you stated you are doing). Seeing as we haven't had rain for a very long time, I'm sure your panels are completely dry by now. Good luck!
3. I think all you have are water stains, not rot. Celotex tiles are kind of like cardboard/chipboard, not real wood. Real wood is what gets rots that spreads. I *think* the worst that can happen on the celotex is that whatever panels have the stains are the ones that need to be replaced, and if you can contain the leaks on the roof, you shouldn't have a bigger problem. I use Eastman Contracting, a roofing firm, for some good patching on the tar & gravel roofs, if you wanted to spend $65 for a full roof inspection, and then they would patch the areas in question. Their phone number is (408) 971-9000.
4. They're like giant sponges. once they're wet, forget it. and it's hard to find an exact match. may not be available now.
5. Our leaky roof soaked parts of our Celotex. It has dried out—important to do. Our roofer saw no need to replace the Celotex. I will add that when Celotex gets wet, it can sag, but that can also be old age, too.
Replacing Celotex Panels Completely
If you have experience re-sheathing your roof (ie, removing all celotex panels from the beams and replacing with plywood or other solid material) before installing your external roof material (e.g., T&G, spray foam, membrane), can you please share your experience here? (Query posted by GMason, June 2011)
2012 Update - I can answer my own question, now that I’ve completed the task of removing the Celotex layer and rebuilding my roof completely. I knew my 18 yo tar & gravel roof had to be replaced due to leaks, but I wanted to go further and remove the Celotex layer too. I removed the Celotex panels for 2 reasons: 1) it got wet from roof leaks and was sagging, crumbling & falling down, and my repairs looked bad and 2) I wanted a better looking ceiling for aesthetic reasons. After some research and several discussions with MV building dept, I learned that stripping the roof down to the rafters/beams and re-sheathing it counts as a re-roofing project and can simply be handled with a re-roofing permit (thus, no engineers or architects needed). I discussed with the City my plans to rebuild the roof before I sought out a roofer, so I knew what was possible and required in advance.
I initially wanted a spray foam roof but passed on this option when I learned this approach would require 2 separate contractors, one for carpentry work (sheathing, fascia, replace dry-rotted rafters, etc), and another for the spray foam work. This is unnecessarily complex and could lead to finger pointing if a problem arises, so I found a single roofer who would take responsibility for the both activities. I selected Bill Hamilton Roofing (BHR) who handled demolition, re-sheathing, insulation, replacement of dry rotted beams & fascia, and installed a single membrane roof (IB roof systems).
I rebuilt the roof with these layers:
1) 1x6” T&G planks (my ceiling); planks were sealed/stained prior to installation
2) 1/2” structural I plywood (required for seismic strength)
3) 3” rigid foam insulation (R-19 minimum, per codes)
4) Gypsum fiberboard (fire protection)
5) Single-membrane roof - 80 ml IB Roof Systems PVC roof
Note: 2x6” planking could have replaced the need for structural plywood, but a structural engineer would need to sign-off on this approach, as per the MV bldg dept.
I also upgraded my electrical service panel, added electrical circuits for new lighting, painted the rafters/beams, installed skylights and a PV solar system too. I functioned as a general contractor to coordinate these various trades, although each trade pulled its own permits and all timelines were driven by the roofing activities.
It took six weeks from demolition to final sign-off of the roof work by the City inspector. It is now week #9 (Sept 2012) and I’m not completely done yet, as the electrical work is still ongoing (I was late ordering the lights), but there’s light at the end of the tunnel!
As usual, there were problems along the way, but I stayed involved throughout the entire process to ensure I was satisfied with the end result. This would be my strongest advice to anyone considering doing this type of project, or any remodel project for that matter. Do not completely turn your project over to contractors. Stay involved, review the work carefully (be there when they're there) and be prepared to make changes as the situation dictates. Remember, the contractors work for you, and you don’t work for them. You pay the bills and you’ll live with the results, so stay involved and make sure you’re satisfied with the work.
I’ve posted specific comments about my experience working with the individual contractors (Bill Hamilton Roofing, Chris Gray Electric, Sigura Painters, Horizon Energy Systems) in the contractor referral section of this Wiki.
A final note about Celotex panels, since I think few folks would actually remove them completely. The original panels installed on my John Mackey built house in 1955 were about 1-1/2" inches thick. Later, these panels were manufactured with about 2-1/8" inches thickness, and the 1-1/2" inch panels were no longer available. My roof had been previously repaired in certain spots and the original Celotex panels were replaced with newer panels. Thus, the height of the roof surface was uneven due to the patch work done. This could have contributed to the pooling of water on my roof and subsequent leaks. Anyone replacing damaged Celotex panels today would be creating a similar situation if the roofer is not carefully adjusting the height of the roof surface to ensure water drains appropriately. Good luck!
Gene Mason on Thompson Ave (posted Sept 2012)
Update - Oct 2014
The wood beams on my MacKay house had always made a lot of noise (cracks, pops, etc.) during movement and from changes in temperature, but switching from celotex panels to wood planks increased this by several fold. I know to expect noise from expansion/contraction of wood, but it is something I would research further to see if there are methods to employ to lessen the movement in an all wood ceiling and beams. When speaking to Bill Hamilton about this, he noted that another client of his had recently conveyed this same observation to him. I wouldn't undo the switch to a wood ceiling, but would research stronger fasteners, etc to see if they would help. GMason Thompson Ave
