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Mold on roof - tung-oil used


Hi All,

I’ve had my flow hive out in the wide world since January, with 2-3 coats of tung oil (100% tung oil - from the woodworks.com). After doing an inspection today, I noticed that the roof is getting very moldy. The hive is in partial shade (we’re in sunny Bris - and have been through 38 degree days this summer so i’m reluctant to give the hive full sun). It’s pretty sad that it’s deteriorating within a matter of months.

Any thoughts/advice on how I should treat it?


Pretty normal from what I have seen with oil finishes outside. I usually paint mine a pale colour to help with the heat from direct sun.



I would call that “smog” - we have the same. Just rinse it off away from the hive, and wire wool (0000 grade if you really feel you have to, otherwise don’t) and then repeat again next month! :blush: In 6 months, if you feel you are down to bare wood, just put more Tung Oil on. I have extra roofs available in case I need to do this.


Do you know for sure that your tung was not cut with linseed oil? Linseed will mold Tung should not.


The website states very definitely that it’s pure tung cut with nothing.

Thanks @Dawn_SD, looks like I just need to add another job to my beekeeping checklist :slight_smile:


Vinegar wipe will help prevent mold


It’s just your climate. There is no moss here, but some places roofs on houses have moss. Sidewalks have moss. I would just not worry about it…


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I’ve had exactly the same thing occur. Three coats of tung oil in Dec last year. The cause was winter and the wood not drying out. Now that it’s warm and the wood has dried the issue seems to have gone.


I am having the same problem, but the mold got there over the first summer. We didn’t even put them outside until June of last year. They are certainly not the pristine, picture perfect look that we have seen in photos and videos – sadly, they’re actually more of an eyesore.

Has anyone come up with a better option than tung oil to preserve the beauty of the cedar and still be safe for the bees?


I saw other set-ups before I got my Flow Hive & saw the molding as well. I thought I’d find a water based stain & go w/it instead of the Tung Oil for the roof.

After assembly & sanding, I treated the screened bottom board, boxes & roofing frame w/a 70/30 treatment of The Real Milk Paint Company’s Citrus Solvent & Pure Tung Oil. I applied two coats of this followed by a sanding between coats. I then treated it all again w/two more coats of 100% Pure Tung Oil w/a sanding in between them as well. The same was done to my custom made Western Red Cedar Hive Stand.

As for the roof, after sanding, I used Cabot’s Semi-Transparent Deck & Siding Stain to give it that Log Cabin look. This has all been out in the weather since June of 2016 & am happy to report that it all still looks as nice today as it did the day I put it outside.

I don’t know if this is the better idea you were looking for, but it’s the better looking idea I came up with…



Your hive looks GREAT! Thank you for sharing! That’s the best suggestion I’ve heard so far and I think that sounds like what I need to try. I’m not sure how to accomplish it since bees are already in the hive, but I think I could at least do the roof by replacing it temporarily with a different one.

Thanks again!


Your hive looks great! Thanks for your help.


Hi Dawn,

Were you able to purchase extra Flow Hive roofs, without ordering the set?

My 2 roofs are being beat up by the Texas sun and I need to figure out what to do to refurbish them. In the Spring, I put 2 coats of Tung oil on them before we got the bees. I will need to remove the covers to apply more tung oil, but feel I’ll need temporary replacement roofs in the meantime, while I work to fix up the original roofs. Will it confuse the bees if I get another type of cover for temporary use? Is it best just to wait until cooler weather in the fall/winter to refurbish, when they aren’t so active?


I didn’t try. Mine was repairable. However, @Faroe might know whether it is possible to do this.

I have never found that. For orientation about hive placement, all the bees care about is how the entrance looks. I don’t think you need to wait for winter. To be honest, they would probably be fine for a couple of days with the roof off and the hole in the inner cover closed up. If you have very hot weather, I might put some reflective insulation (like a car windshield shade) over the top of the hive. Otherwise, they will be fine.

If you are taking them off, I would suggest going to Ace or Home Depot and getting some wide aluminum flashing. You can then cut that to fit on top of the A-frame and under the shingles, screw the roof back on and Tung Oil or marine polyurethane varnish it. Now you have “belt and braces” to keep the hive weather proof. :blush:


Why don’t you just putsome metal sheeting on the roof? Water and weatherproof.



After a year in the weather my mothers Cedar roof was quite weather-beaten. I took it off- disassembled it- hot wax dipped all the parts and put it back together with a layer of aluminum flashing over the A frame screwed underneath the top slats. I also added some more screws. If you can’t have someone hot wax dip the parts you could simply paint the roof slats. This should protect it and make it last much much longer- as well as making it watertight.


Sorry to hear you have got mold on your roof. We have updated our faq now on our website to include information about tung oil and mold occurring on wood.
Basically, the mold doesn’t affect the structure or the strength or your hive, but it might not look good :wink:
And mold occurs depending on area, humidity etc.


We have heard from one beekeeper experimenting with mold removal, and refinishing. Here are some pictures.

She used Oxygen Bleach (100% Sodium Percarbonate).

Sodium percarbonate is a chemical, an adduct of sodium carbonate and hydrogen peroxide (a perhydrate), with formula 2 Na2CO. 3 · 3 H2O2. It is a colorless, crystalline, hygroscopic and water-soluble solid. It is used in some eco-friendly cleaning products and as a laboratory source of anhydrous hydrogen peroxide.

Once the mold is off you can try using something with a mold prevention in it, or use an outdoor waterproof paint/sealant/stain, etc.

She is in the process of now of testing different finishes on different woods to see how they hold up in the wet weather.

The roof is just natural timber (Inside) with no paint on it and that cleaned up well.

We have one post in our forum explaining all the different types of waterproofing people have tried on their roofs:


Just had an ironic thought. In the US, Oxalic Acid is sold in hardware stores as “wood bleach”. Maybe soaking the roof in that would remove the mould and help with varroa control!!! :smile: :stuck_out_tongue_winking_eye:



All great info ! I might try that recommendations someday. As long as my bees are dry n safe I’m in not panic ! :yum:. I’ve got bigger fish to fry like mites, moths, lost queens, nectar flows, harvest (not) n more ! :ok_hand:

Thanks for the great feed-back n notes young lady,