Basic pre-paint wall prep


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Old 02-06-07, 05:50 PM
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Basic pre-paint wall prep

I often get accused of spending too much time on prepwork vs. the actual paint application. So please clear up some confusion for me.

For simplicity, lets say I have a living room painted 8 years ago with eggshell/satin latex (some SHEEN), just average "dirt" (kid prints,no smoking), no major repairs (few nail holes). Going to reapply same type of high quality product, no drastic color change.

I have people tell me they never wash walls - "just paint 'er". Scuff sanding is unheard of. Some say they regularly prime the walls to "lock in the dirt" and assure good adhesion. Comments?

1. Wall washing. What say ye? Do you professionals do it? Many paint cans still recommend TSP. Is there something or some way that is better? A silver bullet??

2. Scuff sanding. On eggshell/satin is it necessary? Could someone outline this procedure and best materials - a fast way - professionals can't afford to spend a day sanding? Do professionals really do this in the real world?

3. Priming. I've read past posts about when it's required. What about using it INSTEAD of the washing/scuff sanding on these eggshell/satins? Save time? I understand (correct me) that a properly prepared wall can be repainted with similar product without priming.

4. Liquid Sanders in a bottle? Yes? No?

5. Number of coats (yea, I know, not prep question). I almost always put on two "lighter" coats instead of trying one heavy coat. Is that a crime?

Thanks in advance!
 
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Old 02-07-07, 06:41 AM
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#1 - it is always better to paint over a clean wall, dirt/grime can affect adhesion, usually not a problem unless the wall has more than normal.

#2 - it never hurts to sand, a scuff sandign can be done quickly, I usualy only spent a few minutes per wall using a pole sander [what drywall finishers use]

#3 - the main reasons for priming are to seal bare or repaired walls or to hide/cover stains. it may also be necessary when applying latex over oil base.

#4 - generally no

#5 - 2 thin coats are always better than 1 heavy coat, I usually let the wall and the paint decide what is needed for full coverage.
 
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Old 02-07-07, 12:59 PM
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Originally Posted by slowbutsure View Post
I have people tell me they never wash walls - "just paint 'er". Scuff sanding is unheard of. Some say they regularly prime the walls to "lock in the dirt" and assure good adhesion. Comments?
That's one of the most incredulously ridiculous excuses for shortcutting I've ever heard
It would be funny if it wasn't so horrifyingly wrong
That's a great way to have your paint job fail
Maybe it'll fail right away, maybe it'll fail a few weeks down the line, maybe it'll fail when repainting a few years from now, maybe it'll work just fine...a few times
Just because someone 'gets away with' a bad practice a few times, doesn't mean it a good practice
Don't listen to those people any more


Originally Posted by slowbutsure View Post
1. Wall washing. What say ye? Do you professionals do it? Many paint cans still recommend TSP. Is there something or some way that is better? A silver bullet??
TSP is the silver bullet
But check with the paint inst.
Though I wouldn't recommend it w/o seeing the wall myself, just to let you know I will skip cleaning walls in great shape that will be sanded

Originally Posted by slowbutsure View Post
2. Scuff sanding. On eggshell/satin is it necessary? Could someone outline this procedure and best materials - a fast way - professionals can't afford to spend a day sanding? Do professionals really do this in the real world?
I always scuff sand
An exception might be going over a recent flat paint

I use a sanding screen on on a pole
The avg. room takes minutes rather than hours

For trim I use sanding sponges

Originally Posted by slowbutsure View Post
3. Priming. I've read past posts about when it's required. What about using it INSTEAD of the washing/scuff sanding on these eggshell/satins? Save time?
Save time? No
Seriously, it takes much less time to wash/sand than paint/prime

Not to mention the time you spend scraping the paint and primer off of after it fails for being applied to a dirty, slick, wall

Originally Posted by slowbutsure View Post
I understand (correct me) that a properly prepared wall can be repainted with similar product without priming.
Correct
There are only a few reasons to use primer in a re-paint

Originally Posted by slowbutsure View Post
4. Liquid Sanders in a bottle? Yes? No?
They have their uses
It's unlikely the avg. DIYer would run into the need
Certainly not a basic room re-paint
Not at all


Originally Posted by slowbutsure View Post
5. Number of coats (yea, I know, not prep question). I almost always put on two "lighter" coats instead of trying one heavy coat. Is that a crime?
The preferred way, and the industry standard, would be two lighter coats instead of one heavy coat
 
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Old 02-07-07, 07:34 PM
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Thank you very much for taking the time to answer all the details of my lengthy post. It's reassuring to know that I am more or less on the right track. Your answers help put into perspective the required prep time/effort - ie., washing and sanding should be quicker than priming/painting.

You see the apartment painters and the diy'ers doing the wam, bam, thank you ma'am technique and start wondering if that's the right way.

I think I'll stick to being a good painter, but not necessarily a fast painter.

Thanks again.
 
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Old 02-08-07, 06:00 AM
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In my experience, good preparation for painting is almost more important than anything else. It also takes most of the time. It seems that many folks are concerned about the price of a can of paint while ignoring the amount of time it takes to perform the complete job or repeat the work if it fails.
 
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Old 02-08-07, 07:39 AM
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1. TSP indoors? No way. Unless thourghly rinsed. And I mean water running down the walls wet, there is a good chance you will leave some TSP residue on the walls. That is going to be a bigger adhesion issue than its worth. If your walls are truely "dirty" use a waterbase cleaner such as simple green, or even just toss a little 409 in some water and wash that way.

Unless you have actual dirt, or grease on the walls, washing is way over the top as far as surface prep goes. HOWEVER if there are smokers in the house that changes the equation completly. You will need to not only wash the walls, but prime them as well to cover the nicotine and tar that will bleed through to the next coats.

2. Not needed unless you are painting over a semi/full gloss. Technically you will achive better adhesion over a scuff sanded surface, but realistically, a good quality latex coating will have decent adhesion to hold up to a cleaning.

If you do sand, make sure to wipe down the walls. If you don't the sanding residue will interfere with adhesion and possibly cause failure.

NEVER sand paint in a home older than 1976. The potential for lead contamination can not be overstated. Best to simply paint over, but if you are concerned, contact a qualified lead abatment contractor for help in resolving this issue.

3. Priming: Generally not needed unless coating semi/full gloss. Also helpful if wall being painted has marker/crayon/oil stains/ or a very deep color.

Generally 2 coats of topcoat would be sufficient.

4. Liquid sanders are a poor choice. Unless you change your rag frequently you risk contaminating the entire surface with oil/surface dirt.

Hand sanding is much more efficient, and smells better also.

5. 2 coats is fine. Better than trying to get it all with 1 coat. Less chance of runs/sags.
 
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Old 02-08-07, 11:25 AM
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groundbeef,

Thank you for throwing in a challenge and creating some debate.

No TSP? Why then is it so often listed on the paint can labels?

Take a look at this product I saw a local pro using, and tell me what you think. While it claims no rinse, it doesn't mean wet the surface and let the resulting soil/liquid mess sit there:

http://www.greatlakeslaboratories.com/ Is this my silver bullet?

Go to "products" then "No rinse Cleaner"



Semigloss walls? Are you saying that priming is mandatory in ADDITION to sanding or INSTEAD of sanding?

Thanks again.
 

Last edited by slowbutsure; 02-08-07 at 11:28 AM. Reason: Add info.
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Old 02-08-07, 01:06 PM
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TSP is a solid product, don't get me wrong. However, for interior use, there are now several products that work easier, and require less work.

TSP has some abrasive qualities, so when washing semi/full gloss coatings it does tend to knock the shine off. This is an advantage, as sanding is usually not required. However, these very same properties also require a very thorough rinsing. If not done well, a "dust" will remain on the surface. It can (and usually will) reduce adhesion.

Simple Green, 409, even reduced windex does NOT require rinsing after washing. These products do not leave a film or "dust". Simple green in higher concentrations can also dull the finish of glossy coatings. And it smells like black licorice.

Also, the waterbased cleaners are non-hazardous, unlike TSP where it is suggested you wear gloves to avoid skin irritation.

Paint Cans recommend a lot of things. Perhaps TSP is recommended because it is generic, and not trademarked. But if you ask the paint store, most will recommend other products.

I'll look up your product, but if its like Simple Green, its probably fine. Great Lakes puts out some nice products.

BTW "No Rinse" means just that. However, remeber to change your rag, and change out the water if it starts to look dingy or gray. After all, you don't want to keep slopping dirt around, you want to remove it.

As far as semi/full gloss the choice is yours. Either lightly sand/wipe walls, or prime. If the paint has been done prior to 30 days to repaint, I wouldn't bother with either.

You don't need to do both. This is assuming of course that you are using an adhesion primer designed to stick to glossy coatings. Cheap drywall primer ain't gonna cut it!
 
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Old 02-08-07, 04:13 PM
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my 2 cents

I've used TSP on and off for many years and never heard of anyone using it inside of a residence until joining this forum. As already stated it is a good cleaner and promotes bonding of the new paint BUT it must be rinsed well. Easy to do with a water hose or pressure washer on the exterior but inside ...........
 
 

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