Eight Tips for Maintaining Your Mahogany Deck


Mahogany is a great wood for outdoor decks, be it Cambara mahogany from South America or Meranti mahogany from Indonesia or the Philippines.  It has a tight grain, does not splinter easily, is free of knots, and looks great when treated.  But it is not perfect.  It fades.  It loses that rich red-brown color and turns grey.

The criminal here is the sun, specifically, its ultra violet rays.  They will bleach the color out of any wood, including mahogany.  If you block out those nasty UV rays – with a roof or a thick canopy of trees – then mahogany will keep that rich color.  But you have no such luck.  Your backyard mahogany deck is totally exposed to that evil sun.  So what do you do?  You need to block the UV rays, and that is best done with a pigmented, oil-based, protective coating.  The pigments block out the sun’s rays and also add color.

Fortunately, treating your deck floor is not difficult;  it is project that you can do in an afternoon.  Here are some tips. (I specifically address mahogany here, although these tips apply generally to any wood deck.  For tips specific to pressure treated decks, see my blog post on Restoring PT.)

1. Why treat your mahogany deck?  Treat it because it has faded to grey and you want to restore its original, rich color.  Using a quality protective oil will extend its life.

Ready to re-treat

2. When: Treat your deck when you no longer like its color.  Test it:  if a drop of clear oil (or water) soaks into the wood within a few seconds, then the oil treatment will also soak in.  But if the oil or water stays on the surface for five seconds or more, then wait.  The oil treatment will not properly soak in, and your deck is not ready.

Maybe ready

3. How often you need to treat your deck is a function of how much direct sun it gets.  In full sun, it will need treatment yearly.  So treat it when it is new – ideally after the first rainstorms wash it but within its first few weeks of life.  Thereafter, to maintain its good color, treat it yearly — or less frequently if it is shaded.

4. What parts of the deck you treat similarly depends on how directly the sun strikes each.  On south facing decks, the sun hits horizontal surfaces directly, so you’ll need to treat the deck’s floor, stair treads, and rail tops most frequently.  The sun is kinder to vertical surfaces, like rails, risers and deck trim;  those you’ll need to treat only every several years.

5. The treatment you use is important.  Mahogany is a fairly dense wood, but many commonly available “deck treatments” are relatively thick and will not soak in. They can lie on the surface and eventually flake off.  Use a penetrating oil formulated for mahogany.  Five are available:

I have informally tested each of these on Cambara mahogany in my backyard.  For longevity – holding color the longest – Cabot’s Australian Timber Oil, “ATO”, mahogany flame color, is the best.  Penofin’s Brazilian Rosewood oil is second, and I find its price (about $50 a gallon) a disadvantage compared to Cabot’s ATO, at about $35 a gallon.

One note about color.  Most of the penetrating oils are available in shades of brown. If you want to restore the natural reddish color in mahogany, choose Cabot’s ATO mahogany flame;  it is very popular.

5A.  New Formulas.  (May 2014)  Several years ago, the EPA required that companies modify their paints and stains to reduce air pollutants.  I recently began comparative testing of Cabot’s new “water-based”  preservatives.  (Technically they are not “water-based”, but they do have lower levels of volatile organic compounds.)  Initial, premature results are surprisingly positive:  the new formulas hold color slightly better than the old oil-based versions.  Yes, I said “better”.   My sample stained mahogany boards will cook in the sun for at least six more months before I have viable results, and then I will report those results in another blog article.

5B. Stucco.  (June 2011)  A reader’s recent question led me to investigate an unexpected problem with stucco walls adjacent to decks.  Stucco is alkaline (that is, non-acidic, with a high pH).  If not properly cured and painted, stucco can react with rain water to create an alkaline solution that “attacks” any adjacent, newly applied deck preservative.  It can extend drying time, discolor the preservative, and cause it to fail prematurely.  Cabot formulated a new version of its ATO preservative to survive an “alkaline attack” from stucco.  Ask for ATO series 19400 from your local Cabot retailer.  For a more detailed explanation of the problem that stucco can pose to stains and paints, click here.

6. Read and follow the manufacturer’s directions on the gallons of penetrating oil you paid so much for.  Admittedly, they will be conservative, but the manufacturers are the experts.  And you might even learn something.  Like:  apply only one coat of penetrating oil.  A second coat will not soak in properly and will leave a shiny, uneven mess.

7. Getting the deck ready has two considerations.  The deck must be clean and it must be dry.  Cleaning a new deck is simple:  sweep the dirt off and hose it down or let Mother Nature rain heavily.  If your older deck is stained or is spotted with mold or algae, it may require some scrubbing with a deck cleaner that has a mildew killer or a borate to eliminate algae, followed by a thorough rinse.  Some good deck cleaners are:

An alternative to chemical cleaners is power washing with plain water.  Power washing machines can be very powerful – sometimes too powerful.  They can seriously damage the wood (i.e., make it fuzzy, which is very difficult to fix).  To avoid that damage, set the power level fairly low (certainly less than 1500 psi) and start with the wand’s nozzle far away from the deck and slowly lower it as you sweep back and forth.

Begin 24” away; and watch carefully as you lower the nozzle.  You want to blast away the dirt, grime and stains but not blast away the wood surface.  I am serious here: “blast” is exactly what power washing does.  You’d be wise to practice on some scrap wood.  Use a slow, steady motion.  Technique here is important for getting an even appearance, for the effects are dramatic.  If you are unsure, hire a professional to power wash.  And do not power wash in bare feet.  That water stream will draw your blood in an instant.

Insure that the deck is dry.  Seriously dry.  If it rained lightly on Monday, do not treat the deck on Tuesday.  Wood dries from the outside in.  When it feels dry on the outside, it’s probably still wet on the inside.  You do not want the penetrating oil to trap moisture inside the decking.  After moderate rain, wait at least two days;  three days is better.  The manufacturers advise “3 to 5 days minimum.” You want the moisture content below 15%.  I know: Who has a moisture meter?  A deck that is high in the air, that gets lots of sun and lots of wind will dry faster than a low deck in the shade.  After cleaning then, you’ll need at least five dry days:  three or more days before you treat the deck, one day for treating, and a final day for drying. Temperature and humidity significantly affect drying time;  cooler temperatures and higher humidity extend drying time.  The manufacturers recommend 45 or 50 degrees minimum for the entire time — which is 12 hrs or 24 or more.  So 55 during the day is OK, but night time temps that drop to 35 degrees will delay drying.  To meet the new VOC rules, manufacturers have removed solvents from their oils and that also extends drying time.

7A. Clogged Decking (June 2013)  Here’s a photo of my sister-in-law’s deck.  Notice any problems?
Clogged decking 2 mid

Exactly.  The gaps between floor boards are clogged with…junk.  Natural junk — tree seeds, bits of leaves, pollen, etc. — but still junk.  You must clear all of it away.  It prevents your deck from breathing and draining properly and, worse, it holds moisture that will accelerate rot.  Clearing it may be tedious, but you must remove all of it.  Use a putty knife to force the junk up and then sweep all of it away.  You may need to scrape the edges of your decking to thoroughly clean it.  Were I cynical, I’d tell you that clogged decking is a self-correcting problem:   Do nothing and the problem goes away.  Yeah: your deck flooring will rot away, and you’ll have to install entirely new flooring.  Costing you $thousands$.

 

8. Treating the deck is not difficult.  The penetrating oils are thin and go on easily.  Use a lamb’s wool applicator pad or a good brush (2 ½” or 3” wide for 1×4 mahogany and 4” wide for 5/4 x 6 mahogany).  Do not use a roller; it is likely to put too much oil on the deck.  Pads and brushes more easily control the application and also “work” the oil into the wood.  Stir the can thoroughly before you begin.  You need to mix all those beautiful pigments and solids throughout the can.  We do not want a splotchy deck.  When you’ve stirred it enough, stir it some more.  Now it’s really ready.  The actual application technique here is simple but critical.  Brush one board at a time, over its entire length.  You may treat two adjacent boards simultaneously, but use the space between the decking boards to control the wet edge.  The board you are treating is wet, and the board next to it must be totally dry.  Paint stores sell a simple tool you may find useful: it looks like a single venetian blind with a small handle. A plastic version, called a “trim guard,” is also available.  It will fit easily between deck boards as you brush and will prevent any oil from overlapping onto the dry board.  You may be tempted to treat a larger area a few feet square – that would be more efficient, especially if your knees are as tired as mine.  If you do, however, the edges of that area will partially dry before you can treat the immediately adjacent area, and you’ll get double coverage.  Wet oil over partially dried oil will create a streak that is darker than the rest of your deck.  These dark, overlapped areas are ugly and cannot be fixed.  Your deck will be uggg-ly for years.  So, treat the entire length of each board.  If you’re in the middle of a board and the phone rings, ignore the phone.  Keep going.  If the President of the US arrives unexpectedly at your house and asks your advice on international relations, ignore him and keep treating.  Do not let the oil dry before you reach the end of that board. Once you finish a board, you may stop for lunch.  Take a break, whatever.  Have I overstated this?  Am I being redundant?  I hope so, because double covered lap marks are HORRIBLE.  If you disregard my advice, two things will surely happen:  your deck will be uggg-ly for years, and I will come to your house and dope slap you.  Got it?

Watch out for two other issues.  As you treat, have a rag handy and wipe up any excess oil that does not soak into the mahogany within 5 or 10 seconds.  Clean up any pools of oil.  If you apply too much oil, your deck will be shiny and tacky — for a long time.  Secondly: Beware of oil dripping over the deck edge.  You probably cannot see over the edge when you are treating, so check frequently (after you finish that board) or have a friend or your spouse watch for this.  Your spouse may even enjoy pointing out your mistakes as you crawl along on your hands and knees.

Treating your mahogany deck is a labor of love.  It’s work, but you’ll love the results.

Other helpful links:

We at Archadeck of Suburban Boston offer professional design and build services for clients west and north of Boston.  Over the past 21 years we have designed and built over 700 projects, including over 200 mahogany decks.  We have enhanced the depth of our expertise by limiting our work to decks, porches, and sunrooms.  To view some of these projects, visit our website.  To learn how we treat our clients, check our ratings on Angie’s List or read about us in an article in Remodeling magazine.  For a free design consultation and a relaxed and rewarding experience, contact us via e-mail, subboston@archadeck.net or by phone, 781-273-3500.

© 2010-2013, Advantage Design & Constr., Inc.

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Categories: Deck care, Deck maintenance, Decking, mahogany, Restoring decks, Treating decks, Wood deckingTags: , , ,

39 comments

  1. Dear Deck Boy…

    I just loved your tips on treating. I guess I should stop using my husband’s old shorts and use the lambs wool instead. Boring, but the deck will be beautiful.

    Thanks a million…Muffy

  2. It’s me again. I’ve been looking at my deck and see that it has faded unevenly. It’s not mahogany. I think it’s pretty much just plain wood. I can’t imagine what it would look like if I tried to power wash it…even if I wear shoes! What should I do to get the deck ready so the new stain will go on evenly? I don’t want the same thing happening with the new treatment.

  3. You seem to favor ATO. Other sites say not to use it ever. I just power washed my 12×22 mahogany deck. It is twelve years old. In the past I have used “Superdeck Brand Products” db1910 natural. It is from Duckback Products. My supplier went out of business.

    What should I use and should I sand the surface. Thank you

    • Thanks for the comment, John. My favoritism for Cabot ATO stems from my testing it — and other penetrating oils — on mahogany. In two tests, about six years ago and again two years ago, I found that ATO holds its color longer. I also like the choice of colors ATO offers. And another benefit I find valuable is Cabot’s excellent field service — on request, they have visited a particularly troublesome deck to help me determine a solution.
      But back to your deck, John. I hesitate to recommend sanding without seeing your deck. But here is the crux of the issue. Power washing often does not remove all the old, hardened preservative or paint. You must get the entire deck surface cleaned down to bare wood. If your deck looks splotchy now — darker spots among areas of bare wood — then it will look splotchy after you re-treat it. Be careful how you sand: a powerful belt sander used carelessly will damage your deck. For suggestions, see my blog post about sanding PT wood. The same principles apply to mahogany.
      One final suggestion: take pictures of your deck (including close ups) and contact Cabot’s Technical Support center at 800-US-STAIN. They may help analyze your deck and recommend solutions. Good luck and tell me how you did.
      — Jim Finlay

  4. We are preparing our mahogany deck for application of the Cabot oil and were wondering what the effect of sanding the deck would be. The deck was built five years ago and has not been touched since. It has a full day of sun exposure so it’s in pretty bad shape. Will sanding hurt the wood?

    • Lindsay,
      Carefully sanding your deck will not hurt. Be sure to set the screws or nails below the deck surface, otherwise they can damage your sander. If you have experience with a belt sander, it can be very effective, but be careful. Its power and speed can be difficult to control, and it could gouge the mahogany. I’d recommend 100 grit, or perhaps 80 grit — nothing coarser. It’s critical you sand with, not across, the grain. A random orbital sander will be much kinder to the wood surface and is more tolerant (its random motion allows you to sand in any direction). Good luck.

  5. Hi Jim, I’m learning a lot, thank you for sharing all these tips.
    I just installed new mahogany deck wood on my 3 season enclosed porch, and was wondering if it is safe to treat it with the Penofin Hardwood Formula or if I should use something different because it’s enclosed.
    thank you!

    • Keren,
      You’re safe. The roof and walls of your enclosed porch will not affect the process of treating the floor or the product you select. Your roof will keep the floor drier than an exposed deck, but I’d still warn against treating on a rainy day. Open the windows to assist drying time, but even then your floor will take longer to dry than if it were outside. And be especially vigilant to wipe up any excess oil that does not soak into the mahogany within 10 seconds. Be sure to plan just where you will finish (at a doorway) — we don’t want you boxed in a corner waiting for the floor to dry!
      — Good luck,
      Jim Finlay

  6. Jim, t
    his website is very helpful! My husband just built a beautiful deck last summer that was ‘Mesmerized’ with a one coat finish. He sealed each end after cutting. Now we have a slightly graying deck and I would like to restore it to its brilliance from when the wood was delivered. I don’t know the species of mahogany but it was so varied, with redplanks, some planks with tiger-eye gold stipes, purple planks, dark burgundy, etc. We used the colors to plan out the trim edges, etc.

    What I want to do is restore the brightness. It sounds like using an ATO that is tinted wouldn’t meet my needs. Is there such a thing as a clear coat that you would recommend? ALso, is there such a thing as a deck cleaner that you would scrub on, like with a broom, and then rinse off? We bought a deck cleaner but I don’t know if a generic cleaner would be species-specific or if it’s ok.

    Thanks Jim! – Cori

  7. So glad I found this site with all this information. We had a mahogany deck installed 10 years ago and never sealed it. About 5 years ago we asked a painter how to return it to it’s original mahogany look and we were told the only way to accomplish this was to paint the deck. Needless to say it looks horrible. Can we power wash with a good cleaner and then finish with the Cabot’s Australian Timer Oil??
    Thank you !!

    • Lisa: Power washing will certainly help. (Make certain whoever power washes your deck is experienced and uses proper technique.) You may have to sand the mahogany as well. I expect a “good cleaner” will not be adequate. You may need a much stronger wood stripper. Cabot’s offering is called “Problem Solver Wood Stripper”. You could call Cabot for detailed guidance: 800-877-8246. Good luck.

  8. I’m trying to decide between Mahogeny and pressure treated wood for the railings. We probably will be painting the railings in either case to conform to the look of the rest of the house. Given that it will be painted, is there any reason to go with the more expensive mahogeny?

    • David, The advantages of mahogany over PT wood are several, but most significant are better dimensional stability, lower tendency to splinter, and more attractive appearance. Because PT shrinks considerably across its grain, joints in your rail will open noticeably, the posts will check, the top rail cap may cup significantly, and the stair handrail or bannister could splinter dangerously. Mahogany is a dramatically better wood than PT, but the cost difference is also dramatic: twice that of PT. For a large deck, that difference could be thosands of dollars. Wow. Beauty lies in the eye of the beholder, but splinters may lodge in the hands of your guests. Consider a combination: frame your rail in PT, but use mahogany where hands touch — the top rail cap and especially the stair handrail. And do not paint your rail. Stain it. Paint flakes over time and will require scraping. Stain fades gracefully away. Semi-transparent stains display the beauty of wood, and solid stains are available in literally any color. Don’t pay all that money for mahogany and then hide it. Save your money — but protect your hands.

    • David: Mahogany is more dimensionally stable than PT; for a well-built rail, however, that advantage is minor. Most people choose mahogany for its appearance — but if you plan to cover the rails with a solid stain, where’s the advantage? By the way: never paint wood rails (or decking for that matter). Paint is a film and will flake or peel off over time, and require laborous scrapping or sanding. Apply a good quality stain instead. Cabot and other companies make solid stains for outdoor wood in almost any color. They breathe and will not flake, resulting in easier re-treatment year later.

  9. I have two questions:
    We just installed a mahogany floor on a newly built screened in porch. I want to preserve the color with the suggested Cabot’s Austrailian Timber Oil.
    (1) When should I apply the first oil treatment?

    The railings on the porch are PT wood and we are waiting until Spring to put the stain on the PT wood. (2) Should we put polyurethane over the stain… especially on the inside? Will polyurethane make the stain hold up better?
    Thanks

    • Bonnie: Treat mahogany directly after installation. The only reason to wait would be for good weather – dry and temperatures in the 50s or warmer. Never apply polyurethane to a wood deck. It will flake off over time. Use a penetrating oil. We recommend TWP for PT decks. It is available on-line from MFG Sealants.

  10. Hi, our mahogany decking seems to have swelled this winter in Massachusetts. There is no space between boards will the mahogany decking start shrinking as the weather warms up? Thanks

  11. Hi,
    Your page has been extremely helpful for us as we clean and plan to treat our Mahogany deck. We have gotten the Mahogany Flame from Cabot. A neighbor said oils sometimes turn the decking black with time, mold, sun.
    Is this something I should worry about? I have seen the result of the Mahogany Flame oil on another small deck we have. It looks great now. Will it last or turn black, making treatment harder the next time.
    Thanks so much

    • Philip,
      After treating your mahogany deck with ATO mahogany flame, you can expect it to weather slowly and gracefully. ATO does not encourage mold growth (which appears as black spots), quite the opposite. No worries.

  12. Confessions from a serial deck abuser……. I can’t believe all the things I have been doing wrong all these years to my poor deck. From this day forward I will let my deck dry for at least three days, get rid of all the junk between the boards, return the new roller I just bought, nor more power washing and damaging boards…..Thank you for all of the helpful hints.
    A newly reformed deck abuser!

  13. Hi, we have a new mahogany deck. We are looking to let it silver up. Unfortunately tradesman have walked clay across it which looks like has now become baked into the deck by the sun. I tried a test patch using a water blaster with a circular brush which I thought would would be of milder application (not direct blasting), however this resulted in affecting the grain of the wood and leaving a burred look. I have been told that after a winter of rain and elements this should naturally clean the deck, however, i’m not so sure and is a long time to wait. Can you recommend a way we can clean the clay off our deck without damaging the grain of the wood. Thanks

    • Bansky,
      I suggest you try a 3:1 solution of water and Cabot’s Wood Cleaner (#8002), allow to it to stay wet for 10-15 minutes and then rinse off with moderate pressure (a garden hose at high pressure should suffice). I have noticed in the past that dirt/mildew embedded in the wood may take more than one application to adequately clean. Good luck, Jim Finlay

  14. I am about to install a cambara deck. I ultimately want the deck to have a natural grey weathered look. Is there a way to let the deck turn grey but keep it safe?

    • Ned, I have two different thoughts.

      1. You want a grey deck that is still “safe”. Cambara mahogany is naturally rot resistant. Just let it weather and do not treat it. I am unsure what you mean by “safe”. An untreated cambara deck will last a long time before it fails – 10 years? 12? More? Longer if it is high enough to have good ventilation underneath. Probably longer if it is treated with a preservative.

      2. Mahogany preservatives try to keep the wood’s rich color, and they do so primarily with pigments that block out the sun’s ultra violet rays. Those pigments would color the wood you do not want colored. That said, I suggest you let your cambara weather to the grey you like and then apply a “natural” color preservative, one that adds the least pigment. Cabot ATO has a “natural” version, as does Penofin. Save some scrap cambara boards and let them weather like your deck. Then you can test several preservatives on the scraps before you apply your choice on your deck. Tell me how it goes.

  15. Jim, We have a mahogany deck that was constructed about 6 years ago (May 2008). It is fully exposed to sun and the elements. After it was installed I treated it with Cabots ATO and it looked beautiful that first year but the next year it was terrible . . . blotchy, near black spots here and there. However, the rails, spindles and lattice were not bad. I have since had it sanded by a professional wood floor guy three times and restained (the year before last with Sikens Water Base Stain and last year with Sikens Oil Base Stain. All stains were “transparent”. Each time it looked like new but the next year it was back to the same problem. We’re thinking about having it re-sanded and restained again in the next couple of weeks. Any suggestions on staining/treatment that will better endure?

    • Jack,
      It’s hard to know what’s happening to your deck. “Blotchy, near black stains” makes me think of mold, but mold normally does not grow when fully exposed to sunlight. Sanding your deck will remove the top layer, but may drive some mold spores deeper into the wood. I have two suggestions. Rather than sanding try a deck cleaner and deck brightener. I’ve had good results with Cabot’s “Problem Solver Deck Cleaner” and “Problem Solver Wood Brightener”. Better: Take pictures of your deck problems, send them to several stain manufacturers, and ask for their analysis and recommendations. They have experts, perhaps biased experts, but you can compare several responses. Good luck.

  16. We have a mahogany deck that was installed two summers ago. It gets a lot of sun on half of it. The other half is under a porch overhead so not as much sun. We are about to stain it and like your recommendations. Question is, a railing has to be painted as well that goes along the porch. Which should we do first? The porch or the railing? The railing is primed already so we feel as though it can wait but the deck has been left untreated for two summers. I hope we aren’t too late….

    • Jen, Rather than painting the railing, I recommend stain. Paint can peel and flake; stain penetrates better, ages gracefully, and is available in any color. That said, I’d suggest you stain the rail first. Protect the floor below with a drop cloth. If some stain does get past your pretection, you can wipe / sand it clean before you finish the floor – preferable to cleaning drips on a newly finished floor. Good luck.

  17. Do you have any fastner sugestions other than top screwing with stainless screws? And should I consider treating all 6 sides of the decking before I install the decking or install and stain later?

    • Kevin,
      Over time we have tried several “hidden fastening” systems on mahogany 1×4 and been disappointed. Tiger Claw clips do not pull the mahogany tight to the joists and create a deck surface that is slightly uneven and squeaks when walked on. We briefly tested the Camo system and found that it too frequently split the sides of our 1×4 mahogany. Smart Bit’s screw and plug system performed best, but required we sand the entire deck after the glue dried — a significant effort. Thus, we continue to face screw our mahogany 1×4 decks. Swan’s 316 grade stainless steel trim screws perform well and their painted heads (“ipe” color) blend well visually.
      I do recommend pre-treating all sides of mahogany installed on low decks. Less than about 18 inches of ventilation below a deck will prevent the mahogany’s bottom surface from drying properly and can lead to premature failure. That’s failure spelled “R-O-T”.

  18. Jim, thanks for keeping this blog running. Good info. I have a good sized 600 sqft Cambara Mahogany deck here in NH that is well-ventilated and while south facing gets pretty good shade for much of the afternoon. It’s about 7 years old and has received Mahogany Flame ATO – the original petroleum-based version from the start and again 4 years ago. It still looks great but needs a new a redo. I’ve heard some negatives about the new low VOC formulation of ATO, mostly by people who had used the old petroleum version like me.

    I wonder what your opinion is about making that transition. Also wonder if you have any experience or heard about Timber Ox Green, a Bio-based formulation from the midwest using castor bean, citrus, soy and corn oil which seems to have a lot going for it and some pretty enthusiastic advocates. Thanks,

    Karl

    • Karl,
      Thanks for your encouraging words.
      Good questions. I recently began a comparison test of Cabot’s new, low VOC ATO (series 19400) against their older, oil-based ATO (series 3400). Initially – after only two months in direct sunlight – the new low VOC holds its color better. So I am encouraged about the long term prospects of the new formula. Once the test results are definitive, I’ll report them in my blog.
      I have no experience with Timber Ox Green, just what I’ve read on their website. Sorry.

  19. Thanks for all the great info.

    Regarding the 19400 vs 3400 series. I am in NH, and was informed that the 3400 series has not been available for over 5 years due to regulations. Is there somewhere in NE that the 3400 can even be purchased if desired? Also, I am about to install new mahogany. What are your recommendations for spacing? From what I understand 1/4″ is best for around this area. Do you agree?

    Thanks

    • Mark,
      Yes, the older Cabot ATO (series 3400) was oil based and was withdrawn from the market in most states because it did not meet the new VOC regulations. I do not know where you can buy any series 3400 ATO. But the new series 19400 does meet the VOC regulations, is readily available, and seems to hold its color better than the oil based 3400. I say “seems” because my informal testing is preliminary — After only 2 1/2 months, the new 19400 ATO looks noticeably better. (See paragraph 5A above.)

      When spacing mahogany boards, ventilation concerns are more important than geography. Decks lower than about two feet high or taller decks enclosed with perimeter skirting often lack the ventilation needed to let the deck boards dry thoroughly after rain. The resulting damp environment below encourages rot that can take years off a mahogany deck’s life. Thus, for mahogany decks lower than two feet high (or with limited ventilation), I recommend 1/4″ spacing between deck boards. That 1/4″ helps some, but does not solve moisture issues. Decks with better ventilation do well with only 3/16″ between.

  20. Extremely helpful information. We installed a mahogany deck last summer for a client–all the wood except a small triangle runs in the same direction, the triangle we installed on a diagonal. My client was not happy that the wood on the diagonal always looked different than the main part of the deck—even tho we treated all the mahogany exactly the same with a Sikins oil stain. To make the diagonal look more like the main deck when looking straight down the deck, we added another coat of the stain a few days later—that seemed to do the trick–but here comes the bad part—after a year the double stained triangle still has some color and is totally blotchy—-the rest of the deck has gone silver grey and is ready for a new coat of stain or sealer. My question is how do we get the blotchy finish off the triangle—should we sand it? would we have to sand the whole deck (it’s a very large deck, cooked in the sun most of the day)
    Thank you in advance, regards, Renate

    • Renate,
      Diagnosing problems like yours is difficult at best, especially over the internet. Penetrating oils (Sikkens included) need to soak into the wood. In fact, their labels often warn against applying another coat too soon. I expect the second coat you added “a few days later” did not penetrate thoroughly, but stayed partially on the surface and weathered inconsistently – hence the blotchy appearance. For an even appearance, sand that offending triangle before re-treating. Getting the triangle to match the rest of the deck will be tricky. Sanding the remainder of the deck offers the best probability, since that would bring all parts of the deck to the same state. When all parts of the deck appear the same, treat the entire deck. Good luck.

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