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Should exterior stucco on Tudor style home be sealed?

  • Paint is the best way to seal stucco that I know of. – Ed Beal Mar 25 '16 at 13:34
  • Stucco should never be painted. It becomes an ongoing maintenance nightmare and can trap water if the wall's flashing is less than perfect (which it usually is). – iLikeDirt Mar 25 '16 at 14:51
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If your house's wall was built correctly (maybe not), then the stucco should be able to get wet--soaked, even--without it impacting the structure beneath. You would be in the danger zone if:

  • You live in a very rainy climate
  • Your roof has stingy or no overhangs
  • the water-resistive barrier layer under the stucco is something less than two layers of grade D building paper (common in houses built after 1980)
  • The sheathing underneath the water-resistive barrier is OSB (common in houses built after 1980)
  • There is plastic sheeting underneath your house's interior drywall and you use air conditioning (common in houses built after 1970 in Canada and the northern part of the USA)

The more of those that are true, the more risky stucco is on your house. By "risky" I mean "more likely to cause hidden structural decay and mold growth inside the walls."

So if you decide that too many of those factors apply and you want to do something about it, what do you do?

First of all, don't paint the stucco with standard paints. It makes future repairs more expensive, and it's also dangerous because they don't breathe, so water that does get into the stucco becomes trapped there. Water stays in the wall longer and the paint will bubble as the water tries to escape through it. You'd be signing yourself up for a lifetime of maintenance.

You can paint the stucco only with special masonry sealer products called "silicate mineral paints." These are paints that seal out water but allow any trapped water to escape as a vapor. A basic one can be created yourself using pure sodium silicate. These products harden to rock so they do not have any maintenance associated with them.

You can also apply a new thin layer of stucco on top with these silicate mineral paint waterproofing additives into it--or other suitable waterproofers. The important part is that you need something that blocks liquid water but is permeable to water vapor.

  • I have been across Europe a few times and stucco is used in the rainiest coldest places there, also seen most nice houses in rainy/humid Brazil are stucco. Not sure where you are going with the rainy bit. – DMoore Mar 25 '16 at 15:29
  • It is my undstanding that modern stucco is basically mortar. I would agree it shouldn't be painted but could be sealed as if it were a concrete block or brick. Buildings have been built with brick, mortar, and stucco for centuries now without the need for sealer, though it may extend its lifespan. – ArchonOSX Mar 25 '16 at 15:52
  • Outside of the USA, stucco is usually applied over stone, not wood. If the stone structure gets wet, no problem. Not so with stucco-clad houses with wood frames. – iLikeDirt Mar 25 '16 at 16:44
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It won't hurt & would only be beneficial, though not actually necessary. A clear masonry sealer would be best & will need re-application every 5-years, regardless of claims or brands.

For any stick-work, those should be correctly caulked. Meaning, just enough to forcibly finger-fill the gap & wiped clean so only the pin-strip of caulk in the gap is visible, instead of an ugly heavy bead of caulk that will fail quite quickly...less is more.

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