Removing Old Paint from Block

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Old 12-24-14, 01:46 PM
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Removing Old Paint from Block

Began prepping old block walls in the basement for Drylok this morning by removing the old paint. Spots of the old paint are bubbling and easy to remove, but most areas are still holding strong. I started with a wire cup on an angle grinder, but the extreme amount of dust made me switch to a manual wire brush....which will likely take an eternity. Power washing isn't an option. Are there any tricks to remove paint from block walls? I'm hoping for a miracle here! Thanks for the help!
 
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Old 12-24-14, 02:27 PM
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Is it really necessary to remove the paint? There are some sand blasting methods but I don't think that it's necessary.
 
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Old 12-24-14, 08:30 PM
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Drylok must be applied to bare block to function properly and be covered by the warranty, a secondary concern.
 
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Old 12-24-14, 11:29 PM
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I didn't know that it was supposed to be applied to bare block. You didn't mention the original reason for using drylock. I hope it's not to stop water from entering the cellar. That won't work.
 
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Old 12-25-14, 03:42 AM
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Do the walls currently have paint on them or is it drylok? You can recoat drylok with another coat of drylok. What is the current condition of the coating on the walls? How much moisture is coming thru the block. As Pulpo said, waterproofing is best achieved from the outside. Sometimes it's as simple as redirecting downspouts.

It is very difficult to remove all of the paint from block. Pressure washing or sandblasting are the best methods but neither are ideal for inside a basement.
 
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Old 12-25-14, 08:28 AM
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The walls have OLD paint on the them, the condition is poor. Some areas are peeling, some are not. There is a small amount of moisture coming through the block, but never water running down the wall. The goal is to get rid of the moisture before insulating with foam board. All downspouts are run properly away from the house, and I would like to avoid digging up the foundation for a minor moisture issue.

To avoid another dust storm in the basement, I will likely continue with a wire brush and maybe a scraper blade on a recip saw.
 
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Old 12-25-14, 08:54 AM
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About all you can do is clean it up the best you can do and then apply the drylok. Anywhere the block is bare, the drylok might seal but where there is paint, it will just be another coat of paint. I would not rely on drylok alone to seal the foundation wall.
 
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Old 12-25-14, 02:53 PM
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Waterproofing needs to be done outside, not inside.
Read the can of Dri-Loc, it's says do not apply over paint on the can I have.
Gutters, grade slopping away from the foundation, no mulch piled up against the foundation.
The old paints bubbling because the trapped moisture is forcing it off the wall.
Unless that wall is always dry your going to end up with mold growing behind that foam and most likely will not stay attached to the wall without some mechanical fasteners.
Foam also can not be left exposed.
 
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Old 12-25-14, 04:23 PM
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I certainly agree that water issues should be handled from outside.I also agree with Joe that dampness behind foam can lead to mildew issues if installed as sheets.

Perhaps a better approach would involve cleaning the wall as good as you can of peeling paint, verifying that you indeed have no water seeping issues and then having closed cell foam sprayed onto the wall .

The foam will bind to the wall and hypothetically eliminate any air gaps which contribute to the formation of mildew. The foam would, like any other form of the material have to be surfaced with an appropriate fire barrier that is code approved for your area. That barrier may be drywall but can also be an intumescent paint...again depends on code in your area.

If you persist in your quest to remove all the paint from your block, I can tell you I have used a devise known as a needle scaler which usually would operate with compressed air but there are rotary scalers that are perhaps available to rent from masonry specialty supply houses. This is one such devise but again it would also lead to dust which you can control with an air scrubber and negative pressure machine , both rentable devises.

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Old 12-25-14, 06:18 PM
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And then have to also rent a compressor that can produce from 8 to 16 CFM if you go with a needle scaler.
 
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Old 01-02-15, 03:13 AM
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just selling our aurand machines now so we can replace them w/newer models incl factory fitted dust shrouds but that's another story yes, a needle scaler will work & you may still be using it when you apply for soc security,,, i realize a h/o-diy'ers time is cheap but there's gotta be a limit some place,,, IF we used scalers, we'd never get the work as the $ would be outrageous

IF your moisture problem's VERY small { how does 1 define that ? }, drylock products may work,,, we don't like the stuff but here goes as to how we would approach these problems.

paint removal - sds-shank bushing tool on a bosch sds + hammer drill - we jury-rigg'd a dust shroud around the tool & that hooks up to a vac,,, you don't need 100% removal so don't get anal,,, just get most - no remaining spots larger than 3/8 - 1/2" square & 90% of the wall should be clean,,, be prepared for pitting of the cmu's

coating application - 3/4" nap roller & frame's possible but we like mason's brush,,, we use either kryton or xypex

keep in mind you aren't stopping wtr from entering the wall - just blocking its transmission thru the wall,,, at some future time, you will revisit this problem again it will cost more as the necessary work will be more extensive incl probably block replacement
 
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Old 01-02-15, 10:04 AM
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Thanks stadry, given that I have access to a hammer drill I'd like to give your method a go. I do need some help with the acronyms, specifically SDS and CMU? I am a bit concerned about removing too much block, especially since this block dates back to the 1940's. Do you think this will be an issue? Also, do you recommend any certain brand of bit? Thanks
 
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Old 01-04-15, 01:18 AM
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you know what a jacobs' chuck is on a drill ? those 3 fingers that squeeze the drill bit's shank & hold the bit in place ? sds is another method of attaching a bit to a drill - much MORE secure - you can't hammerdrill w/jacobs' chuck worth a ****,,, sds is the smaller size - sds+ is the next size shank up & sds max is the largest

cmu = concrete masonry unit ( conc block ),,, block from the 40s MAY be cinder block so you correctly should be cautious
 
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Old 01-04-15, 04:34 AM
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Thanks stadry, I will be using an SDS max rotary hammer with the bushing tool...we'll see how it goes.
 
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Old 01-04-15, 05:58 PM
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they're not easy to find in sds size however you should be able to score sds+ in a rental shop,,, other chucks are spline & improved sds,,, both work fine - we have sds, improved sds, & spline bosch hammers

you may also find a grinder will work well IF you can stand the clouds of dust,,, apron/vest stores have grinders w/shrouds to which you can hook up your wet/dry vac
 
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Old 01-05-15, 04:07 PM
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I have a bushing tool ordered in SDS max size, should be here in a few days.

I used a grinder with a wire brush cup....the cloud was way too much to deal with and it only did an ok job. I suppose a grinding wheel would have done a better job at the expense of some block.
 
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Old 01-06-15, 05:27 PM
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That bushing tool on the rotary hammer is like the easy button for paint removal - works great!
 
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