My suggestion would be to contact the adhesive manufacturer directly and ask the question. The manufacturer should know what chemicals would adversely affect their products.
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Well for what it’s worth I have had bridges out in the weather since 2005, I pull the wooden ones and the wood decks and store them inside over the worst of the winter. They are made from Redwood (Old Growth and/or heart wood second growth) all glued with TightBond 3 and brad nailed at every joint.
Each spring they get a sloppy coat of used motor oil thinned with diesel before they are re-installed. Have never had a glue joint failure, some of the soft wood between the growth rings is starting to erode from weather but the glue joints are fine.
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Possibly however …" In my honest opinion does it really matter" ?
What are your expectations for longevity and maintenance? I only have experience with different materials outside for 15+ years some were fail and many were finds?
Just asking that’s all?
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I need to reiterate because you are talking cedar shingles…now I need to ask what is the subsurface and especially the PITCH that the cedar shingles reside on?
Hi Rooster
Some of my buildings are 15 or so years old but until we built a garden had never been out in the weather.
One roof has liquid nails on a piece of cedar board as a shingle base.
On the other shingled roofs are attached by silicone caulk to a cedar board.
The pitch is 45 degrees.
The 1st building I constructed has the liquid nails as a fixative for the shingles to attach to the building’s cedar roof The shingles are held together by a polyurethane (foaming) glue. The glue turned out to be too gloppy to use as it foamed out through all cracks and I did not find a satisfactory way to clean it up before or after drying.
I moved on to painted styrene corrugated roofs and aluminium metal corrugated roofs that were satisfactorily quick to assemble, but as I have tons of shingles, I have gone back to the tedious placement of shingles.
On the other buildings everything else is either tightbond 2 or 3.
The shingles of the original building in the foreground loved absorbing water in the first few minutes of a light sprinkle.
I’m quite happy to maintain the buildings as long as what I do isn’t counterproductive to extending their longevity.
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Bill, I come late to the party but looking at your quandary I would stay away from petroleum based products.
From the net:
In general, silicone is not compatible with petrol. There are, however, some silicone-based products that are specifically formulated to resist fuel.
When silicone rubbers come in contact with mineral oil, silicone rubber can undergo physical and chemical changes
Therefore personally I’d lean more to a thinned down wash of Titebond III as a sealent for your roofs. Set up a test with some shingles in place with your preferred adhesive then coat that with the Titebone wash. Let it dry and see what happens when you apply water to it. Hose it down, lay a wet rag over it for a few days, see what happens to the test set up.
JMHO YMMV 
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Thanks David,
That’s what I’ve been concerned about. I think I can try the watered down tightbond on my oldest roofs, but i had quite a bit of silicon ooze with the silicon bathtub gutter seal.
Any thoughts on silicon spray such as 808?
Never used it but silicone spray should be fine. Just remember you won’t be able to paint over the sprayed areas
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Thanks David I’ll give silicon spray a trial run.
My other option to try in non glued areas was to try citronella oil with Bifenthrin that would cover weather proofing, ants infestations and possibly repel mosquitoes.
I doubt I’d get the perfect trifecta as no one has mentioned it on LSC but I still may give it a go in safe areas.
Maybe I missed something but do you really plan on leaving those beautiful and delicate buildings out in the weather all winter?
Ooh Rick,
You’ve hit my weak point… should I leave them out at all? Should I even put them out? They took forever to build…
…and I was just starting to accept the LCS central argument that buildings have a finite life span, but there are ways to extend that life. And as folks on this thread have pointed out, waterproofing might do just the weaken the buildings and shorten their lifespan.
Your post came at an appropriate time…
…as it came just after my test placement of the buildings, when a freak wind blew one wood and both plastic buildings off the raised garden bed. The Pola came apart and took 3 days to glue together. The mine office scuffed up a bit and has a dent or two.
Rick, am I correct in assuming you get snow and ice?
Heat is probably our biggest concern here. Adelaide reportedly is the sunniest city in Oz and it’s not unheard of getting 40-45 (104 to 113F) degree days in summer which incidentally starts today Dec 1, but also gets very wet winters, hail occurred just after we laid out the lawn. It gets down to freezing here for a few hours each year but we don’t get snow or ice.
Additionally we have sprinklers that seem to aim water at the building sites.
It has been suggested I place a box over each building, when not in use, however, I kind of want to look out the window at night and see a warm glow of light pouring out of these windows.
Here’s what it looks like when I remove all but the plastic buildings from the garden. The rear part of the garden is building rich and vegetation poor.
So, Rick, thanks for asking. Your post certainly has become a point of discussion with my wife on where we go with this.
Go with the Titebond 3 glue!
Staying on topic as suggested/recommended.
Bill,
Our Summer days can hit 105-115 but average about 90 degrees. and yes we get snow and ice but not as bad as some other places. Our biggest winter problem is the rain/fog/ and dampness… In my opinion the Summer sun can be as hard or harder on outdoor structures as the winter wet.
The sun will eat up those delicate Cedar shingles in just a few years, I’d worry more about UV protection than water proofing if you don’t plan on leaving them out in wet weather.
As far as life span that can vary greatly. I have structures that are 25 years old and still look almost good as new, but they are stored in the barn all winter and left out full time in the Summer only in shaded areas.
My buildings that stay out year round are built to take the elements ( think 1 to 1 building materials) and lack a lot of fine detail but they have held up very well.
A brick or half a brick will really help the buildings stay in place, unless you have fully finished and detailed interiors than it is a little more problematic. All my structures are weighted one way or another even my building flats made from extruded foam start with a chunk of 2 X 4 or 2 X 6 wood as a base.
Your doing the right thing asking for advice and opinions but the bottom line is we all gotta make the final choice ourselves.
By the way that is a beautiful railroad and those structures are all top drawer.
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Ok Rooster,
We’re going to commit one building to the suggested Tightbond 3 treatment.
The citronella oil with pyrethrums trial water-insect proofing is on the back burner.
The other shingled buildings glopped too much silicone with shingle placement resulting in such a shiny appearance, that I suspect they may be already waterproofed. So we’ll test that theory.
However, Rick still has us thinking about risk management and the prospect of becoming a “fair weather modeller” has some appeal.
I just love this picture! You got sedums and creepers (plants) with rocks but the structure is the best!
Does it (the structure)have a purpose other than looking sexy? Love the roof lines along with the main roof cresting but the…ahh never mind,
Thanks Rooster,
The building is a bungalow that precariously holds on to the highest location on the line. I suspect it will serve as the home of a mine manager after I figure out how to build a poppet-head and a mine shaft. The bonsai next to it was theoretically hit by lightning (having been the highest thing in the area before the thunderstorm).
The most surprising thing of this build for me were the rocks. When our house was under construction I moved these rocks 4 times to get them out of the way for the various tradespeople, and each time I grumbled and asked myself why am I keeping such ugly rocks when I have flagstone and slate.
When I washed and placed them, their dull rust streaks and veins of sparkling quartz revealed themselves.
Yes mostly creepers in the garden. I double potted the bonsaii in deeper pots and buried them in such a way that hopefully I can pull them out and trim them without disturbing the surrounding soil.
Well all you need is the “gallows” and cabling with a shed to cover the hole. Unless you really wanna go over the top and rent a 3’ auger …lol
We were discussing sun/UV damage earlier, here is an example of about 4 years in the sun full time.
I just started replacing the roof and thought I would share this with you. The shingles were glued down with Silicon and had a few coats of water sealer over time. Had to use a wood chisel to scrape them off.
Edit. You can’t buy weathering like this 
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Well David and Rooster,
Here’s the follow up…
I committed to your recommended waterproofing recommendations and have done 2 buildings with copious amounts of watered down titebond 3. These 2 buildings have liquid nails as the original shingle adhesive and the 15 year old bungalow revealed another surprise.
I started with the bungalow, the oldest building that I have in my arsenal. In the end I was left with a bit of a sheen on the when finished with the bungalow, but it’s not too distracting.
Now the surprise. I have since learned if I have enough clamps and enough titebond glue I can flatten about anything to a strong straight piece of lumber. However at the time I had not discovered the LSC rule “never use ply”… and have some stained, varnished marine ply under the shingles. I’m at risk of becoming a fair weather railroader! But I digress…
Please note the pictures in the next group should be upside down. My phone has re-positioned all the remaining photos upright. For painting the titebond for maximal coverage, I placed the shingled area upside down to encourage flow under the shingles.
I then squashed the sponge brush into the crevices then blotted with a paper towel to remove the excess. (Turn your device over to see the drops going the correct direction. Ha!)
Photo with Excess glue removed
With some judicious blotting before the glue became too sticky, the second building’s roof has ended up with more of a Matt finish.
Thanks everyone for the advice. I’ll post my adventures with about silicone waterproofing journey on the other buildings, when the silicone spray arrives.
Rick!
I must say, even though adding shingles with silicone is a slippery gooey mess and adds a full day I’ve enjoyed the results.
Had you posted this picture first, I’d be considering putting my buildings back on the shelf, only to be brought out on clear night with a full moon, and changing to building only concrete models.
Was the shingle removal successful and the building survive? Did you replace the shingles with shingles or something more durable?
For the roof on my wayside station I used a styrene corrugated sheet painted to simulate a zinc metal roof. This was the build I referred to that had the warped roof and was the model that convinced me you can’t own too many clamps, and of the miracle called Titebond 3. This roof choice was a real time saver! (Or so I hope.)
