elastomeric coating for stucco

jwasbury · 10-12-2016, 09:57 AM

I know there are a number of builders here on the brain trust. I'm in the midst of a full gut renovation and restoration of a ca. 1910ish tudor style house. The architectural plan requires certain areas of stucco to be patched and other areas are out right new. My contractor has offered up a change order where the stucco guy will refinish all the stucco surfaces on the house with an elastomeric coating.

I appreciate that this is good because the color will be consistent across all the stucco, both new and old. I'm just curious about thoughts on using this type of coating system to refinish existing stucco. Sub-contractor says its the best stuff - what say the brain trust.

Gratuitous photo of the subject:

MRM · 10:34 AM

My practice includes quite a bit of construction litigation, most of it related to stucco installed since the building codes changed in the 1990s. I would strongly discourage any coating on the stucco surface. I don't think you should cover a porous material like stucco with an elastomeric finish that doesn't breathe. My recommendation is to simply have the contractor run a big batch of the finish coat he's applying to the new areas and just skim coat the old stucco areas with the new color coat. Everything matches and everything stays natural.

gr8fl4porsche · gr8fl4porsche's Garage

Good advice above.

Elastomeric coatings form a barrier over the substrate in an attempt to keep water out. They also are designed to bridge over hair line cracks - also in an attempt to keep water out.

In reality they tend to keep water in once it eventually finds its way beneath the coating - and it will find a way. At some point down the road, a crack, failed caulk joint, etc. will let water in and it will have no where to go. They are not breathable.

Elastomerics also tend to degrade (chalk and fade) quicker than standard 100% Acrylic coatings.

If you decide to paint, look into Rust-O-Leum's Water Tight Flexible Primer and Finish. It is an Acrylic with elastomeric type properties while not truly being an elastomeric.

jwasbury · 10-12-2016, 12:57 PM

Thanks for this input. I have to get more details but it's possible that someone already painted the stucco so in that case I'm not sure you can do a fog coat or slim coat. Is that correct?

fintstone · fintstone's Garage

Quote:

Originally Posted by jwasbury

Thanks for this input. I have to get more details but it's possible that someone already painted the stucco so in that case I'm not sure you can do a fog coat or slim coat. Is that correct?

If it is painted, then you cannot fog over the color. In cases where it is painted, must folks just paint it all.

MRM · 10-12-2016, 06:23 PM

"Slim" coat obviously autocorrected from skim coat.

That's a nice vintage house. You don't need or even want all of the stucco to match patina perfectly. It will look unnaturally sterile and contrived if you do. Leave all of the original stucco as-is, patch the replacement stucco as closely as possible but don't sweat the details, and install the new stuff proudly as new stuff, showing that it has new, old and everything in between stucco.

If there is paint on the existing stucco, the only way to remove it is sandblasting. If the paint isn't causing a moisture intrusion issue, then it's working on that application and shouldn't be messed with. If it is, your builder will have found that our and removed it. Just leave the current stucco as-is, patch in the new patches matching as closely as possible to the original and try to match the new stuff to the old. It won't match perfectly (new and old stucco never quite match) so chalk it up to the character of your house and wear it as proudly as the owner of a survivor 356 B cabriolet would wear every crease and dent on his pride and joy.

LWJ · 10-12-2016, 09:22 PM

My first house was a 1914 stucco job. A great exterior. Even in the wet Oregon winter. Don't put a rubber on it.

look 171 · 10-12-2016, 10:42 PM

repair or sandblast then top coat. Existing waterproofing is more then likely gone after 100 years. That's something to think about. I have never been a real big fan of rubber, like LWJ said. The big overhand should keep lots of the rain out.

jwasbury · 10-13-2016, 10:55 AM

Quote:

Originally Posted by MRM

If there is paint on the existing stucco, the only way to remove it is sandblasting. If the paint isn't causing a moisture intrusion issue, then it's working on that application and shouldn't be messed with. If it is, your builder will have found that our and removed it.

Thanks all for the input. I do believe that at some point the existing stucco was painted. There is one rather obvious panel where a large section of the topcoat has failed and peeled off. Aside from that isolated issue, the stucco appears to be in pretty good shape.

Given that this renovation project is otherwise a no holds barred deal, I'm saying no to throwing another coat of anything on the old stucco. Seems to me that if I ultimately want to refinish the exterior, the proper approach will be to remove the paint and fog coat, or if necessary completely strip and apply new stucco.

jwasbury · 10-13-2016, 10:58 AM

Here is a before and after

original rear view of the house:

All new back section...this is where the all new stucco in being applied. Also been trimmed out to match the rest of the house. Trim will ultimately be painted brown to match existing, of course.

Rich76_911s · Rich76_911s's Garage

Looks fantastic Jacob!

I have no input on stucco information, sorry.