This post was updated on April 4, 2025
Hi, I am Scott Paul, a leading exterior restoration contractor and business owner with over 30 years of experience in exterior wood. My RAD Guard Mildew Protection Review is based on my history as a wood restoration contractor and actual hands-on testing, all designed to present you with the top deck stain choices. See here for more info about me.
RAD Guard Mildew and Algae Cleaner and Preventer
We would love to hear from you if you have used the RAD Guard to clean or prevent mildew on your wood or deck. Please post a rating in the Consumer Star Ratings below.
If you have any questions about using the RAD Guard, please ask in the comments below.
RAD Guard Mildew Cleaner & Preventer Product Info
RAD Guard RTU (Ready-To-Use formula) is a no-rinse cleaner and preventative that is safe and effective for removing and preventing stains caused by mold, mildew, and algae on exterior surfaces and exterior wood or deck stain coatings. RAD Guard cleans without pressure washing, scrubbing, or rinsing. Contains no bleach, chlorine, acid, sodium hydroxide, or phosphates.
Pro Tip: Can Be Applied Over Existing Paints, Stains & Sealers
RAD Guard Prevents Mildew For Exterior Wood and Decks
Keeps cleaning long after application, keeping your wood stains looking better longer. 1-2 years of mildew and algae prevention.
Pro Tip: RAD Guard RTU is not used for prepping wood for wood or deck stain application. The primary goal is to remove mildew or algae stains and prevent mildew and algae stains from returning.
RAD Guard Review Scores (1-10)
How I Rated RAD Guard
My RAD Guard review contains a 4-step process and the final average score. Each step is on a scale of 1-10.
- Removal of Mildew and Algae
- Cost Per Square Foot
- Ease of Application
- Final Appearance after 2-3 weeks
- RAD Guard Final Score
4-Step Review of Rad Guard
1. RAD Guard Removal of Mildew and Algae: 10
The RAD Guard was applied to a bench that was covered in mildew and alage. Both the algae and mildew disappeared from the bench after about 2 weeks.
Pro Tip: It takes time for the RAD Guard to work. The key is patience and it can take 1-3 weeks for stains and mildew/algae to disappear. The cleaning time varies based on the amount of rain after applying and the severity and the type of stain being removed.
2. RAD Guard Cost Per Square Foot: 8
The RAD Guard covers 200 sq. Feet per gallon for $50. We used less than 1/10th to test this bench.
Note: The RAD Guard also comes in a concentrated formula that will clean and prevent mildew for up to 1000 sq feet.
3. RAD Guard Ease of Application: 10
Very easy. Use a pump sprayer to apply on top of your wood or a fully dry wood stain and let it work.
4. RAD Final Appearance after 2-3 Weeks: 10
It was spotless throughout the application area when it was done. It fully removed the mildew and algae.
Overall Score for RAD Guard: 9.5
– This is a great product to keep your deck looking good in between a full prep and recoating. It will prevent mildew that can grow on top of your exterior wood or deck stains, making your deck look better.
RAD Guard Product Info
Manufacturer: Restore-A-Deck
Product Type: Mildew and Algae Cleaner and Preventer
Available Sizes: 1-Gallon
Application Temperature: 45-95 F
Coverage Per Container: 200 sq. ft per Gallon
Application Tools: Pump Sprayer
Test Deck Stats:
Deck Wood Type: Pine Bench
The Condition of Deck: Black Mildew and Green Algae Spots
*All products tested and results are from our experience. We offer no guarantee of similar results. Consider that results may differ due to different wood types, exposure to UV radiation, and natural weathering.
Hi! Does RAD guard need rain to work? I applied a week ago for dark mold/mildew that appeared last winter on our deck that we had prepped and stained in the summer. It is not raining yet or anytime soon. Does the product need water, should I spray it or leave it alone? Thanks!
No, it needs sun, rain, and natural weathering for it to work. It will remove the mildew but it takes time depending on severe it is. Could be weeks, or longer. Leave it as is for now.
Tech Info: Roof Stains will continue to disappear with subsequent rainfall over the next 3-9 months, Green Algae stains in 1-7 days, and Black mildew stains on non-roof surfaces in 3-12 weeks.
what is the shelf life of this product?
A few years.
what are the ingredients please?
Any idea why these brand new boards developed mildew/mold just weeks after they were stained? My contractor used Penefin.
Also, why did the stain drip all over the deck after a few weeks? There was no rain, only morning dew/condensation.
The rails seem fine but the top boards are all like this. How do you suggest I repair and renew this? Which products and in which order?
Thanks much,
Mike
Yes, that is mildew. Most of this is related to the Penofin itself. Not only does it smell bad, but it has issues with darkening over time. Usually, it takes months or a year, but yours is accelerated. I’m not sure about the drips. It seems it never fully cured.
You should strip and brighten to remove and start over with a better stain brand that does not have these known issues:
https://www.deckstainhelp.com/penofin-wood-deck-stain-photos/
My pine door has developed a midlew problem. I use 3 parts Penofin Transparent Wood Oil to 2 parts Spar Gloss Exteriror Varnish to oil the door each year, and I just don’t know what to do about the black mildew stains. Any help you can give would be so greatly apprecieated. Thank you!
The varnish is attracting the mildew and should not be used on a deck. You should remove it all and use a proper deck stain that does not attact mildew.
Can rad guard be used on my new IPE dock before I oil it for the first time with deck wise IPE oil plus?
No, it goes on after the stain dries and is cured, not prior.
Hi,
Last year I used R-A-D stripper and cleaner to remove the semi-transparent stain from my ~1000 foot cedar deck. I am just letting it naturally gray. It is too much work to keep it stained etc. plus i like the natural look of cedar.
Given this, is the RAD Guard Concentrate 1 Gallon , still recommended to keep the deck in the best shape it can be naturally?
If so, regarding Step 3: Saturate areas to be applied (Do not let RAD Guard puddle) with RAD Guard. Surfaces that RAD Guard is being applied to must be fully dry before application.
Does this mean spray the RAD Guard mix on a perfectly dry deck?
Thanks,
Harry
RAD Guard will help keep the algae and mildew away and allow the wood to naturally gray. It should be applied to a dray deck. Very easy, just spray it on.
I have a covered screened porch with a tongue and groove ceiling. The contractor put an oil base water proofing on it-two years ago. There are a few boards closest to the screen that have some mold/mildew on them. I have washed it by hand but not all of the mold came off. It seems to be under the waterproofing. I would rather not strip those boards in case they will look different than the other boards. Please tell me if your RAD Guard mildew cleaner and preventer would take care of my issue. I would have to apply the product by hand. Thank you for your help.
No, if the mildew is under the coating then the only way to remove the mildew is to remove the coating first.
Hi advice please- porch-roof-over-screened / cement floor (not level). Climate-Daytona Beach=humid-mostly hot-today-cool-60F. My experience with a log home and decks in hot/humid/wet climate is mold. Have used expensive log home water based and oil based deck stain. New PT framing to level. Using (NOT PT) T&G yellow pine treating under boards pre-installation with Borax in boiling water rolled on for bugs. T&G edge nailed with SS nails. Due to condition of new boards I will sand top after the install with 60-80grit then roll on top & edge with Borax/boiling water/roll-on. I will need to lightly wash loose Borax residue. I would prefer a water based penetrating stain – color choice grey. Bought Behr – tested on a loose board and did not like how it looked – tough to make even & bubbles unless wiped after painting.
ADVICE ?? Stain after Borax, air dry, quick wash, air dry, sand 80 grit, quick damp mop wash ?? STAIN SUGGESTIONS … THANKS
You cannot stain new wood right away. It has to weather and then be properly prepped:
https://www.deckstainhelp.com/how-long-should-you-wait-to-stain-a-new-deck/
Once this happens, look at Restore A Deck Wood Stain in the Cottage Gray.
Pic attached is the mold and mildew built up on the oil based stain and after it was power washed off with a lot of effort.
I have a Brazilain hardwood deck at my lake house that is very near the water. The deck can only except an oil based stain and has previously grown mold and mildew very quickly. So thick you can scrap it off with your fingernail. I just had the deck stripped and sanded. I want to know if i apply a new coat of oil based stain can I apply RAD on top of the stain to prevent the mildew build without discoloring the stain?
Yes, the RAD Guard will help here but it is not true that you can only use an oil based stain. Many penetrating water based stains will work on exotic hardwoods. Example: https://www.deckstainhelp.com/restore-a-deck-wood-stain-for-exotic-hardwoods-review/
Hi! We just had a large deck with a couple of levels built with premium pressure treated pine. Some of the deck gets a lot of sun and some is in the shade. We live in the Memphis area on the Tennessee/ Mississippi state line where it gets hot and humid and this summer we had a lot of storms. It only gets snow and ice once or twice a year. How long should we wait to stain the deck and what do you think we should use? I’m so happy to find this site. Thank you in advance for the advice.
See this for tips: https://www.deckstainhelp.com/how-long-should-you-wait-to-stain-a-new-deck/
Scott
Thanks for the great articles.
Working on the stained ceiling of a covered screened in porch. I’ve seen mention in both R-A-D and Wet n Forget posting which state ‘noticeable difference after a rain’. Why ‘after’ rain? Is rain an activator?
If I’m working on the ceiling of a covered porch, would it help to wait 2-3 weeks and light spray with water?
I believe the rain will help to clean it after the product is applied but not sure.
Hi, Scott. We used Cutek oil with colorant three years ago on a large screened in white oak porch. We have cleaned deeply and are reapplying Cutek. Living on a bluff in Tennessee we get a lot of blowing rain and the humidity is typically high. Green algae and mildew are real issues. I am glad to know about R-A-D for future cleaning. Is it sort of like Wet & Forget? Should we apply it after last stain application as a preventative or wait until we see fungal growth? Do you know if it’s okay with this product to add mildewcide or algaecide to it? We don’t want to upset its chemical balance and effectiveness. Also which ones and where to get. So appreciate your thoughts. Maintenance is a bear!
Much more effective than the wet and forget. Apply it now to prevent prior to mildew showing. Do not add mildewcide to it.
I live near the ocean and just had my wood deck and railing painted. Due to dampness in the area, mildew and algae appear quickly. Right now there is none, since just painted one week ago. Would it be good to apply the RAD mildew remover and preventer now, before mildew appears? Is this toxic at all to the environment?
Not toxic. You can apply it now.
How long until pets can walk / lie on the deck after application?
As soon as it is fully dry.
Scott, what is the typical drying time after application? (Or how can you tell when it’s fully dry to let pets walk on it?) Thanks.
2-4 hours.
Thank you for the quick response. I’ll give RAD Guard a try. (I wasn’t impressed with wet and forget, but love RAD stripper and brightener so I have high hopes for this!)
I have about 1,400 total sq ft (2 decks). I estimate 2 gallons of concentrate will make about 7 gallons @ 5:1 for the initial application, with enough left over to make about 8 gallons @ 9:1 for maintenance application(s) as needed.
Per gallon
@ 5:1 = 13.34 c water: 2.66 cups concentrate
@ 9:1 = 14.4 c water: 1.6 cups concentrate
Does this sound right?
No, there is only one concentration for the RAD Guard concentrate, and that is 5:1. You cannot water it down later for maintenance applications. One gallon of concentrate will make 5-6 gallons when water is added.
I’m confused. The label in the product photo indicates the 9:1 ratio for maintenance (under Step 6).
We always use at full strength when reapplying.
My deck in humid Tennessee has black in areas, how do I know if its6mold or mildew? I only see mention of mildew in the product description not mold.
Mildew looks black when on wood. The RAD Guard will work for mildew, mold, and alage.