The contemporary masonry wall - mjobrien

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The contemporary masonrywall

• Designed to drain• Kept dry with air

cavity• Expected to leak• Uses foam plastic

insulation3 courses = 8 inches(one block course)Through wall flashingWeeps @ 16” o.c.

Flashing• Flashing is our last line of

defense against waterpenetration.

• ANYPLACE the cavity isinterrupted (like for a lintel,or window, or door…) it hasto be flashed to catch thewater and wept to drain thewater.

Ice dams - badEnd dams -

good• Since we usually draw in

orthogonal views (plan, section)we often overlook the ends ofthe flashing.

• One of the most common leaksin architecture occurs at the endof the thru-wall flashing.

• To prevent this, turn the flashing

up at the end of the lintel and

over the brick next to the lintel.

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• The window sill gets flashedbecause it usually has somejoints in it… at least at the ends.

• Here the sloped rowlock sill getsflashed and wept below the sillto prevent water leaking throughthe joints from getting into thewall.

Dams for sillstoo

Sill dams

• At the end of the sill, the flashing

is turned up and over the

adjacent brick to form an enddam

• When the sill canbe cut or cast outof one piece ofmaterial, a designthat turns up theends can preventwater from enteringthe wall at thesides of the sill.

• This is called alugged sill

Limestone Lugs

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Lugs…The way to avoidchemical dependence

• Richardson’s big lug at theGlessner House

Chemically dependent• The absence of lugs

at the ends of this sillmeans the sealant isthe only water barrierat the end of thesill…which may begood for the first tenor twenty years, thenneeds replacement

Efflorescence

What happens when the masonryleaks

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The white powderon the surface atthe arches isefflorescence -salts dissolvedout of the brickand mortar,which moveddown the wall(following gravity)until the saltwater hit aninterruption in thewall (the arch.)The watersoaked in thearch, evaporatedthrough the archface, leaving thesalt depositsbehind

Usually, aconcentration ofefflorescence is asign of a leak.

The leak isusually in a jointor materialchange abovewhere the salt isfound

Water leakingfrom parapetcoping above.

Soakedbricks frozeand the facesspalled off.

No end damat the flashingunder thisslate sill.

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Water can evendestroy largeconcreteelements.

Here, the lack ofan end dam forthe sill flashinghas loaded theconcrete withwater,contributing to thecrack.

Years later, the arch was dis-assembled by removing andreplacing alternating bricks (similar to underpinning.) As is oftenthe case, finding matching bricks was almost impossible. Theflashing was installed correctly and it looks like no leaks!

Setting thewindows at theback edge of thewall instead ofover the cavityincreases thepresence of thewalls mass.

This requiresthat sill flashingand material beof the highestquality as itleaves a deep,low sloped sill tocatch water andsnow.

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A floor bearing in a masonry wall can be an interruption tothe free drainage of the wall. This faint white line indicatesthe sills above have leaked, the water has moved within themasonry downward, piling up at the floor where itevaporates out, leaving the salts on the brick surface.

Leak is likelyhere

Efflorescenceat the top ofthe floor slabbearing on themasonry wall.

If not repairquickly theleaks fill themasonry withwater. Thefreezing andthawing ofwinter andspring canblow the faceoff the brick

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The deterioration is mostly cosmetic, but because thesearches bear load, the weakening brick has to bereplaced.

Go to the deteriorated location and look up to find the leak

Slight rise onthe bottom ofthe arch 1/8”per foot ofspan

The slate copingat the parapethas beenremoved, newflashing installedbelow thecoping and theslate replaced.

The bricks in thearch have to becut out one at atime and newbrick toothed in.

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To save oncosts ofrestoration,some patchingmaterial waspainted overthe brick.

Not verysatisfactory inappearance.

Skewback 1/2”per foot ofspan per 4” ofarch depth

In some places, the cut out and replacement process leftwide, unsightly joints.

Where is thisleak comingfrom?

After all thework ofremoving theslate,reflashingbelow and re-installing it.Some wellintentionedelectriciandrilled a holethrough theslate, throughthe flashing toinstall alightning rod.

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The worst case for the masonry was where it wasexposed to moisture from both sides. What does thecooling tower behind this arch produce? How often?

This arch was deemed too badly damaged,and out of sight so it was covered up withcement stucco. How is the stucco doing?

The corners ofthe coolingtowerenclosure werepatched withsome not-very-close-to-matchingbrick….

Or bondo, orpatchingcompound.

Damage likethis is prettyhard to repairto originalcondition.