problem painting porch

Discussion in 'Painting Forum' started by slootwater, Apr 12, 2010.

  1. Apr 12, 2010 #1

    slootwater

    slootwater

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    Hi,

    I am about to repaint my (non-enclosed) porch. The top coat is latex floor paint right now (did not do this myself, done by previous owners). It flakes kind a bit, since the porch is open on 3 sides and exposed to rain.

    I am debating what the best way is to paint the porch. My original plan was to sand it down completely, and put an oil based floor paint on it.

    However, the house is from 1910 and there are 4--5 layers of paint on the
    porch already. Although the lead paint test kit was negative, I don't trust it. The bottom 2 layers are so hard to remove, I'm kind of convinced it is lead paint anyway.

    So, sanding won't work. I scraped the worst loose paint this afternoon, wondering what to do next.

    I want to avoid just putting another layer of latex floor paint on it: it will
    flake within 2 years and 3 years from now I'll be painting it again.

    The hardware store advised me to put deck stain over the paint. I don't
    believe this can work though. Paint covers wood and stain penetrates it, right? If it has been covered already, how can the stain still do anything?
    Any thoughts on this?

    Alternative: put oil-based primer on it, then oil-based floor paint? Or even just oil-based floor paint and no primer?

    Thanks for any input!
     
  2. Apr 13, 2010 #2

    Cork-Guy

    Cork-Guy

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    You "can" stain a painted deck, just it takes a lot of preparation and won't look anything like it would if it was bare wood. You can use a chemical stripper to remove all the old paint, plus this gives you a lot more control and prevents you from breathing in lead particles. Even with a chemical stripper you should wear safety goggles and some sort of respirator.
     
  3. Apr 13, 2010 #3

    Nestor_Kelebay

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    No, to provide good durability on a floor, every paint company will use it's hardest drying paint as it's floor paint. The problem is that wood outdoors swells and shrinks with seasonal changes in temperature and relative humidity, and the harder a paint is the less elasticity it has to accomodate dimensional changes in wood. Thus, using an interior alkyd floor paint on wood outdoors is sure to result in the paint cracking and peeling as the substrate swells and shrinks. You want to use an EXTERIOR ALKYD paint, which will dry to a harder film than a latex floor paint, but still have enough elasticity to accomodate the range of dimensional change exhibited by wood outdoors.

    What I would do is:

    1. Buy a few gallons of xylene, which will dissolve the latex paint, but not the old oil based paint, which is probably an exterior oil based paint anyhow. Use the xylene and some rags or paper towels to remove the top layer(s) of latex paint(s).

    2. Now, clean the remaining paint use a fairly strong solution of TSP in water. You should be aware that the primary purpose of cleaning walls with TSP prior to painting is the etch the gloss of the existing paint, thereby roughening the surface of the existing paint, thereby increasing the surface area of contact, and thereby improving the adhesion of the new paint to the old. TSP works well in this regard on the old linseed oil based paints, not as well on modern alkyd paints, and doesn't do squat to latex paints. So, if cleaning with TSP doesn't etch the gloss of your porch floor paint, it's likely to be a modern alkyd, in which case you want to avoid inhaling lead paint dust, so that means sand the surface of the old paint down while it's wet and vaccuuming up the dirty water with a wet/dry vaccuum cleaner or allowing the floor to dry and painting over it with an exterior alkyd primer. (alkyd doesn't actually mean "oil based", but I'm saying to use a modern oil based primer if you have to prime)

    3. There is absolutely no point in priming after sanding since primer increases paint adhesion by providing a rough surface, and that you already have. You might want to prime with a tinted primer only if you intend to change the colour of the porch floor.

    4. Now paint with an EXTERIOR ALKYD paint.

    That will give you the most durable paint you can use on wood outdoors because it'll be as hard a you can tolerate without being so hard that it cracks and peels instead of stretching.

    Latex paints (even cross linking acrylics as are used for latex floor paints) simply aren't durable enough to stand up well on a floor.

    He probably meant to strip the paint off and use a deck stain on your porch. Paint is the most misunderstood or poorly understood technology in the entire home center. If you want to learn more about latex paints, then spend some time at the Paint Quality Institute's web site. Unfortunately, there is no comparable web site for oil based, alkyd or alkyd based polyurethane paints.

    http://www.paintquality.com
     
    Last edited: Apr 13, 2010
  4. Apr 14, 2010 #4

    slootwater

    slootwater

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    Thanks for the advice!

    I'll give the xylene a go over the weekend. I think there are only 2 layers
    of latex on there, so that shouldn't be too bad (I hope).

    The Ace sells an exterior alkyd floor paint, that was the paint I wanted
    to try.
     
  5. Apr 17, 2010 #5

    slootwater

    slootwater

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    An update on the porch:

    I tried the xylene this morning. After scrubbing for an hour or so, I stripped about 10 square inches. Yeah, ehm, I do understand it will take time, but with a 400 sq ft
    porch this will take forever. . .

    I was wondering if I'm doing something wrong. How does one use xylene? I just put it on the porch and scrubbed with a rag and a putty knife.

    I `soaked' a small piece of the porch with xylene now and I'll try again in a few hours. Perhaps it needs some time to do its thing.

    Any advice?
     
  6. Apr 17, 2010 #6

    Nestor_Kelebay

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    Well, you've just proven that you no longer have any remaining latex paint on your porch. Xylene will remove latex paint quickly. I think what you're doing is removing oil based paint with the xylene.

    When I use xylene to remove latex paint from kitchen cupboards that were previously painted with oil based paint I:
    1. pour a bit of xylene on the cupboard with a squirt bottle
    2. rub the xylene with my hand for less than a minute until the latex paint dissolves in the xylene, and
    3. wipe up the dissolved latex paint with paper towels.


    My question is: Are you sure the paint you are trying to remove with the xylene is latex paint? If you just want to get whatever it is off your porch, you can always use a paint stripper, but you don't need to remove the old exterior oil based paint.

    I think you're trying to remove old exterior oil based paint with the xylene, and that's why it's not working.

    I regularily use xylene to remove latex paint from oil based paint. The latex paints used for floor are a bit different; they crosslink to form a harder and more durable paint than a wall paint. I didn't think that would matter as my understanding is that xylene dissolves the plastic the paint is made of, so it wouldn't matter whether it was crosslinked or not.

    Please advise me if you are SURE the paint you are trying to remove is a latex paint. You can also test for paint chemistry with acetone. Acetone dissolves latex paints much faster than oil based paints. Acetone is typically the principle ingredient in nail polish removers. If you find that nail polish remover is slow to remove the paint you're trying to remove with xylene, then I think you're trying to remove oil based paint.
     
    Last edited: Apr 17, 2010
  7. Apr 17, 2010 #7

    slootwater

    slootwater

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    > Well, you've just proven that you no longer have any remaining latex
    > paint on your porch. Xylene will remove latex paint quickly. I think what
    > you're doing is removing oil based paint with the xylene.

    You could be right. Even after a few hours, the xylene didn't do that much.
    Acetone didn't do much on the paint in 5 minutes, so that would lead you
    to think that it is oil-based after all.

    My reasons for thinking it was latex was the flaking in spots where it got
    really wet (not much flaking where it remained dry-ish) and the way I
    could peel off a few pieces. Perhaps I was completely wrong, should have
    thought of the acetone myself!

    The status of the porch is as follows at the moment: the worst flaky parts
    have been scraped with a putty knife. There are a few areas that look like
    `scabs'. I couldn't do much with a putty there, but the xylene has some
    effect there. If I put some on it, then I can do a lot with a putty
    knife.

    Would my best plan be to try and smoothen the scabby parts with the
    xylene/putty knife, clean everything thoroughly and just paint with
    exterior alkyd paint?
     
  8. Apr 17, 2010 #8

    Nestor_Kelebay

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    If xylene didn't cut through it in a few seconds, it's an oil based paint. Acetone is used as nail polish remover because the better quality nail polishes are acrylic formulations similar to good quality latex paints. Acetone will cut through any latex paint in a few seconds, and will also cut through oil based paints.

    ANY paint will peel off a substrate that gets wet. The pressure created by the evaporating water will even cause epoxy paints applied to concrete floors to crack and peel. The way to tell if peeling paint is latex or oil based is that latex paints remain flexible, so you'll be able to bend and twist the flakes of latex paint that peel off. Oil based paints dry to a harder and more rigid film that will normally break before it bends very far.

    I would apply the xylene to the rough spots and SCRAPE them smooth with a SHARP paint scraper. I would use one of those paint scrapers with the replaceable tungsten carbide blades because the xylene would probably dissolve the paint on a less expensive paint scraper. I believe that would work better than trying to smooth those areas with a putty knife. Then, I'd clean up with xylene and give the xylene 24 hours to evaporate. Xylene evaporates completely without leaving any residue, so you won't have to remove the xylene.

    If what you have left is oil based paint, my next step would be to clean the paint ONLY with a strong solution of TSP to etch the paint. You should see a dulling of the gloss fairly quickly, so if the TSP isn't doing much good in dulling the gloss, the alternative would be to sand the paint to roughen it. Since there may be lead in this paint, you'd want to wet-sand to prevent the formation of airborne dust.

    Once you have roughened the surface of the paint, I'd prime the bare wood areas only with an exterior alkyd primer. Then paint over everything with an exterior alkyd paint. Give the primer several hours to dry before painting over it, and give the paint a day or two to dry before walking on it. Both the primer and paint will continue to harden with time, but they effectively be fully cured within 30 days.

    For a smoother finish, you might want to add some mineral spirits to your primer and your paint. By adding mineral spirits, you slow the drying time of the paint, but that also allows more time for the paint to self level better. This is important when you're painting with a brush, but is of less importance when painting with a roller because rollers tend to apply the paint smoother to begin with.

    I'll check this thread every couple of hours so that if you run into problems I can respond.
     
  9. Apr 24, 2010 #9

    slootwater

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    I cleaned with TSP last night, the porch is drying now. I hope to prime to bare wood tomorrow.

    It will probably be next weekend before I can paint. [ This is a project for the weekends! ] I have one question left I guess: the paint. The Ace sells an interior/exterior alkyd floor paint. Would that be better/worse than a regular exterior alkyd paint? The fact that it is `interior/exterior' worries be a bit. Usually, is a product is marketed to `do both well', it actually does neither. . .

    Again thanks for all the help and advice!
     
  10. Apr 24, 2010 #10

    Nestor_Kelebay

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    Did cleaning with TSP result in the floor looking duller (less glossy) in the non-traffic areas?

    Also, you need to rinse off that TSP well before painting.

    Regarding the choice of paint...

    I would check with Ace that this product is intended for use over WOOD floors outdoors.

    As explained previously, you need a hard paint to provide good service on a working surface like a floor. However, the harder the paint, the less elasticity it has, and that's critically important for wood outdoors.

    Wood located outdoors expands and contracts due the changes in it's moisture content arising from seasonal changes in temperature and relative humidity. Consequently, to paint a wood floor on an outdoor porch, you can't use an interior floor paint or a hardwood polyurethane. Both would dry too hard to stretch to accomodate wood movement. (You COULD use an interior oil based floor paint or a hardwood floor polyurethane on a concrete or steel floor outdoors because neither will expand or contract sufficiently due to temperature changes for even these hard paints to crack and peel.) However, wood swells and shrinks WAY WAY WAY more from changes in it's moisture content than it (or anything else) does due to thermal expansion. For a wood floor outdoors, you need the hardest paint you can get that will still be soft and elastic enough to stretch to accomodate the swelling and shrinking of the wood.

    So, I agree with your assessment and resulting confusion. Indoors, you don't want to use an exterior oil based paint cuz an interior oil based paint will dry harder and provide better service. Outdoors you don't want to use an interior oil based paint because it will crack and peel off because it can't stretch with the wood.

    I would phone ACE customer service 1-800 phone number, explain the problem and ask if this interior/exterior alkyd floor paint is intended for WOOD floors OUTDOORS. If you get any hemming and hawing, the person at the other end probably simply doesn't know enough about paint to understand the issue, and in that case they're libel to tell you anything just to get rid of you. (They're not getting paid enough to deal with the stress of important questions.) If that happens, I'd just go with any exterior alkyd paint to play it safe.

    You might want to consider adding traction grit to your paint to make it less slippery when wet.
     
    Last edited: Apr 24, 2010
  11. Apr 25, 2010 #11

    slootwater

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    Good plan, I'll contact Ace. And post the result here, in case other people are reading this discussion and are wondering the same thing!

    After the TSP and rinsing of last night, I examined the porch today. It is hard to tell if the porch looks duller, not that much. I'll probably wet sand the top layer. There is no lead paint in the top layer, so if I stay away from the `more bare wood' a bit then I think this would be safe dust wise.

    One practical annoyance: after cleaning with TSP the paint started flaking like crazy again. Amazing, it had gone through various scraping cycles already! Guess I'll be scraping some more tomorrow first :)
     
  12. May 2, 2010 #12

    slootwater

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    An update on my Spring porch project: after lots (ahum) of scraping, I was
    finally able to prime today!

    The ACE didn't really know what to use their interior/exterior paint for (no real surprise), so that paint is out for me I guess.

    However, it seems that no one sells regular exterior oil based paint anymore. I knew about this law that was passed a few years ago, but I didn't think it would be this bad. [ I am very happy that I have vinyl siding! ]

    The only thing I can buy (it seems) is an exterior oil-based barn/fence paint. Good thing is that this is of course especially for wood. The bad thing is that it is gloss, so I think it will get quite slippery when wet.

    Would just adding a lot of traction grit to this paint do the trick? Otherwise, it might have to be the mystery interior/exterior paint after all. . .
     
  13. May 2, 2010 #13

    Nestor_Kelebay

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    I would probably go with the barn/fence paint then, so long as it's an exterior alkyd paint. As a back-up plan, you might try to contact Ace Hardware and ask them what company makes their paints for them. Typically this is done on a contract basis. The manufacturer of the paint would be much more knowledgeable than any one at Ace.

    I'm very reluctant to suggest you use the Ace paint because of the reasons explained in the previous posts. I hope you understand and concur.

    Now, does this barn / fence paint come in several premixed colours? That is, does it come ready made in a "red", or a "brown", or a "reddish brown"? If so, that's done because they can add more pigment at the factory than they can at the point of sale, so a premixed colour will hide better than one tinted at the paint store.

    And I think you should use a traction grit in your paint even if you could buy it in flat. The difference in surface roughness between a flat and a gloss paint is enough to see, but not enough to prevent water planing. You can slip on a wet flat paint almost as easily as a wet gloss paint. But, I've never used a traction grit in any painting I've ever done, so what to use and how to use it is something I can't advise you on. I do know that Sherwin Williams paint stores have a traction grit called "Shark Bite" which you can add to anyone's paint, but whether it's a good traction grit or not, I simply don't know.

    PS: You don't need to know the rest. It explains why you can ruin latex paint by adding too much colourant to it. There's a common misconception that you can ruin oil based paints by doing that too, but this is just a misconception. Oil based paints will be slower to dry if heavily tinted, but will still form a normal film in the end.

    The reason you can ruin a latex paint by adding too much colourant is because the carrier fluid in the 12 different paint colourants in the paint tinting machine in the paint store is GLYCERINE. Glycerine is used as a carrier fluid for paint tinting colourants because it's soluble in both water and mineral spirits, so the same paint colourants can be used to tint both latex and oil based paints. That means the paint store only needs to have space for one tinting machine, and it can tint all the oil based and latex paint they sell.

    The problem arises with latex paints being tinted at the store. Latex paint is essentially a SLURRY of hard clear plastic blobs (called "binder" resins), hard clear or white "extender" pigments that lower the gloss of the paint and coloured particles (called "pigments") (like the white pigment, Titanium Dioxide" that's already present in white tint bases or coloured pigments added when tinting the paint) all suspended in a solution of water and a low volatility (pronounced "slow to evaporate") solvent called a "coalescing agent". Once the latex paint is applied to a wall, the water starts to evaporate, and those clear and hard plastic blobs (the binder resins) find themselves surrounded by the coaleascing solvent at ever increasing concentration. The coalescing solvent softens the clear hard plastic resins so that they're easily deformed (pronounced "squishy"). Then, the same forces of capillary pressure and surface tension that causes tiny water droplets to coalesce into large droplets in a rain clowd work to cause the soft binder resins to pull on and stick to each other to form a continuous soft plastic film with the extender pigments and any coloured pigments suspended inside that film very much like raisins in raisin bread.

    Then, over the next day or two, the coalescing agent evaporates from the soft paint film, and that's what gives you that "freshly painted" smell. (If you smell a freshly painted smell, you're smelling the coalescing solvents, and chances are it's a product called "Texanol". I've dabbled with the idea of buying some Texanol to give every one of my apartments that "freshly painted smell" to impress prospective tenants regardless of whether I painted the apartment or not.) And, as the coalescing solvent evaporates, the plastic film (consisting of binder resins) hardens back up again to the same hardness those resins were before the paint was spread on the wall.

    Now, what happens if you take a gallon of latex paint and add TOO MUCH colourant in the paint tinting machine. Because the carrier fluid in the colourant is glycerine, which evaporates even slower than the coalescing solvent, as the water evaporates from the paint, the concentration of coalescing solvent won't get as high because of all the glycerine. And, the concentration of coalescing solvent in that glycerine is only going to diminish because the glycerine evaporates slower than the coalescing solvent. The result will be that the plastic binder resins won't soften up as much, and the result is that you may not get proper film formation. The result is likely to be a very low gloss paint job that's pale in colour and that you can rub off the wall with your finger.

    The solution to that problem is to add the pigments to the paint to give it colour, without adding any glycerine, and that is exactly what's done at the paint factory when they make a "pretinted" paint (either latex or oil based). Because they can add as much pigment as they want without adding any glycerine, pretinted paints generally hide a lot better because they have more pigments in them than can be added at the point of sale (without ruining the paint).

    Now, all of the preceding doesn't apply to oil based paints. Oil based paints have a very robust film formation mechanism that causes the paint to form a proper film come HE11 or high water. If you add so much colourant that would wreck a latex paint to an oil based paint, all that would happen is the paint would take a lot longer to dry while the low volatility glycerine evaporated from the paint. Once it had evaporated, and the alkyd resins were exposed to the oxygen in the air, then the oil based paint would form a film normally as though there hadn't been any problem. It's just a common misconception that you can ALSO ruin an oil based paint by overtinting it. People figure whatever applies to latex paints applies equally well to oil based paints, and vice versa, but that's seldom true.

    Still, if you can get a pretinted exterior oil based paint, it will give you better hide than one tinted at the store. That's simply because the tint base you buy at the store will be limited by the amount of empty space in the can provided for adding colourant. At the factory, they can add more dry pigment to the paint, and then fill each can full of that highly pigmented paint. At the paint store, they can only add as much colourant as there is empty space in the can.

    If you can get a pretinted exterior alkyd barn or fence paint, I'd jump at that option. If your company doesn't sell a pretinted exterior alkyd, you might want to phone around. It seems to me that a red or reddish brown exterior alkyd barn paint would probably be pretty popular. But, do you want a red or reddish brown porch?
     
    Last edited: May 2, 2010
  14. May 3, 2010 #14

    Todd-Beaulieu

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    I just (FINALLY!) finished a three week porch painting project. The weather dragged the project out.

    Lots of scraping.
    Caulked the bottom joints on the railings to prevent water from getting between.
    Two coats of primer.
    Two coats of California 2010 for the porch structure and railings.
    Two coats of porch paint with the non-slip additive for the decking and steps.

    I really like the grit for the decking.

    After I restore the antique plaque and decorative "wings" surrounding it, the porch will be gorgeous.

    Two things I wish I had done a better job at:

    1. Not letting the paint span the spaces between the deck boards. I hate that look! I was already overwhelmed with the workload, and just couldn't deal with trying to keep them free. Painting inside the cracks was a nightmare!

    2. I assumed the paint would cover rough edges from scraping. It didn't. Scraping the railings was a PITA and often times the scraper would slip and gouge the soft cedar. I lightly sanded, but I should have removed these burrs. They do show up.
     
  15. May 5, 2010 #15

    Nestor_Kelebay

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    Yes, that's why when you paint a house, you sand down the edges of the paint that's sticking well to the house to "feather edge" the paint. If you don't do that, the edges of the old paint will show through as ridges on the new paint.
     
  16. May 6, 2010 #16

    slootwater

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    My porch project is slowly, but steadily, moving along.

    It turned out that the laws in Massachusetts are stricter than I thought: although various stores claim to sell certain paints when you look at their website, they actually don't. No barn paint available! They are not allowed to order oil based paint from their warehouse, all they can do is sell the left-over paint.

    So . . . I ended up with the interior/exterior Ace paint after all. Only available in red and green. We wanted a shade of red anyway, and the red looked OK.

    I painted the porch for the first time yesterday, it needs a second coat. The parts where I scraped don't look that good, but I expected as much. Not a real problem, it is a porch floor, not a piece of fine furniture!

    One small problem though: the red paint looks too bright on the porch. I would like it to look a bit duller for the second coat. Are there any techniques for this? I was considering buying some black oil paint at an art store and mixing it with the porch paint. Just enough to dull the paint a bit. Would this work? Are there any other things one can try?
     
  17. May 6, 2010 #17

    Nestor_Kelebay

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    Eat the politicians. Oil based paints form harder stronger films than latex paints. They're simply a more protective coating than latex paints.

    Darker shades of a colour are called "tones", and you can make a darker tone of your read by adding black colourant in the paint tinting machine. That will darken your paint. As long as it's an oil based paint, it won't affect the final hardness of the paint film; it'll just take longer for that paint to dry the more black colourant you add (for reasons previously explained). You can lighten the paint by adding white colourant as well, and lighter shades are called "tints" instead of tones.

    If you want the paint to be less glossy, then you have to add "extender pigments" which are used to lower the gloss of the paint. Paint stores don't sell extender pigments. However, if this Ace paint comes in different glosses, you can mix a two quarts of flat paint with two quarts of high gloss (say) to get a gallon of satin paint (or any other such combination).
     
  18. May 6, 2010 #18

    Nestor_Kelebay

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    I don't think the traction grit you add to the paint will affect gloss much. Those stones are so large that you can see them. Typically extender pigments are from 5 to 20 microns in diameter, and 20 microns is about the smallest thing that can be seen with the naked eye. (a human hair is about 100 microns in diameter, a red blood cell is about 5 microns in diameter) I expect traction grit is a few hundred microns in diameter.

    a micron is a millionth of a meter, or a thousandth of a millimeter.
     
  19. May 6, 2010 #19

    Todd-Beaulieu

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    Nestor ... I love your answers! Very informative!
     
  20. May 7, 2010 #20

    Nestor_Kelebay

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    Thanks for taking the time to read them, Todd.
     

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