SINGLE WYTHE CONCRETE MASONRYBY JASON YANA

ingle wythe concrete masonry construc-tion is a durable, cost effective and aes-thetically versatile form of masonry con-

struction that is used successfully all over theworld.Single wythe walls, unlike cavity walls andveneered walls, require additional specialattention regarding moisture penetration pre-vention. The following 3 items make up whatis the industry standard for how to properlyuse concrete masonry for single wythe walls.

oncrete masonry units are not all cre-ated equal. Specify and insist on con-crete masonry units which contain

integral water repellent which greatly limitsthe amount of water absorbed by the unit.Specify and insist on the use of integral waterrepellent additives in mortar as well.

S

C1MATERIALS

TREATED UNTREATED

esign and detailing of single wythewalls to avoid moisture problemsrequires the proper flashing details

serve as a line of defense against water pene-tration at parapets, windows, structural floorconnections and at the base of the wall.These details are illustrated on page 2.

D2DESIGN / DETAILING

s with any construction project, requir-ing a qualified contractor with docu-mented experience is critical. Salient

factors for workmanship include proper jointfilling & tooling, proper cleaning, the use of amock-up panels and the application of apost-applied water repellent after comple-tion.

A3WORKMANSHIP

SINGLE WYTHE CONCRETE MASONRY

or years, block manufacturer's have hadthe option of adding an integral waterrepellent additive to their concrete mix-ture during the manufacture of concrete

masonry units. For any single wythe concretemasonry project, specify and insist on units thatinclude this admixture. On the right, untreatedand treated samples of concrete masonry bothhad the same amount of water poured on them,the results are obvious.

F

ften overlooked is in teg ra l wa te rrepellent mortar addit ive. Thecompanies that produce integral waterrepellent also provide bottles of admix-

ture to be added to the mortar. This is a criticalcomponent of a single wythe wall system!Consider using a preblended batched silo mortarsystem such as Spec-Mix, which can ship mortarto the jobsite with water repellent alreadyadded(if requested). The integral water repellentmust be compatible with the water repellent treat-ed cmu chosen for the job.

O

INTEGRAL WATER REPELLENT IN UNITS AND MORTAR

POST APPLIED WATER REPELLENT COATINGS

TREATED

Walls treated with integral water repellent in the unitsand mortar, plus a post-applied sealant outperform untreated walls dramatically

UNTREATED

MORTAR ADDITIVE

MORE INFORMATION

1

ost applied water repellent mus t be used on all single wythe CMUwalls. Adding a water repellent that is specifically made for concretemasonry units will reduce capillary action and limit staining whilemaintaining the appearance and vapor permeability of the wall. It is

important to note that water repellents cannot bridge cracks or voids, oreliminate the effects of excessively harsh cleaning.

Water repellent is not a replacement for poor detai l ingWater repellent is not a cover-up for poor workmanship

On split face cmu consider a silicone emulsion or RTV Silicone CoatingsOn half high cmu and dense concrete brick consider using silane /siloxane coatings

P

Block Manufacturers Integral Water Repellents Post-Applied Water Repellents Batch Silo Mortars Information

www.NorthfieldBlock.comwww.CountyMaterials.com

www.DryBlock.comwww.AcmChem.com

www.Prosoco.comwww.diedrichtechnologies.com

www.nawkaw.com

www.pci-il.comwww.specmix.com

www.ncma.org

masonryadvisorycouncil.org

MATERIALS

SINGLE WYTHE CONCRETE MASONRYDETAILING

FLASHING AT COPING / PARAPET

FLASHING ABOVE WINDOWS & BOND

CONTROL JOINTS

FLASHING BELOW OPENINGS

FLASHING AT WALL BASEUSE RIGID INSULATION ONLY!

METAL CAP

FLASHING

SEALANT

BOND BEAM

FLASHING

LEDGER BEAM

FLOORJOIST

BONDBEAM

WINDOW

SILL

FLASHING

RIGIDINSULATION

RIGIDINSULATION

FLASHING

CONTROL JOINTGASKET

RIGIDINSULATION

BACKER ROD

SEALANT

2" m

in.

2

The parapet is a vulnerablelocation for water penetra-tion. It should extenddown the cmu a minimumof 2 inches and should havea slope for drainage.

Seal underside of the cap toprevent wind driven rainfrom getting under the sill.

Through wall flashing mustbe installed above all open-ings, at all bond beams andat all floor connection lines.Flashing should turn up onthe inside and extend out-side the face of the wall toensure water is directedoutward.

Control joints must beplaced at a maximum spac-ing of 24 feet on center.

Control joints must beplaced adjacent to windowsand doors. For moreinformation on placementof control joints, seeNCMA 10 series tek notes.

Window sills should beprecast concrete or stone,they should have an over-hang and a drip.

Flashing must be installedbeneath the sill with enddams installed on eitherend.

Flashing must be installed at the wall base, and turned upward on the inside. Grade level should be below the flashing level and sloped away.

Block-Flash is shown on the left as an alternative to traditional flashing.

Blok-Flash

DO NOT USE BATT INSULATION!! Use only closed cell rigid insulation toavoid mold, mildew and condensation problems. Below is a list of the IECCInsulation requirements by climate zone. Minimum thicknesses of insulationrequired is shown for extruded polystyrene (XPS) and polyisocyanurate (P-ISO).

2009 IECC Building Envelope Requirements - Opaque AssembliesClimate Zone 1 2 3 4 5 6 7 8

Min. R R 5.7 ci R 7.6 ci R 9.5 ci R 11.4 ci R 13.3 ci R 15.2 ci R 15.2 ci R 25 ci

XPS req. 1.5" 2" 2" 2.5" 3" 3.5" 3.5" 5"

P-ISO req. 1" 1" 1.5" 2" 2" 2.5" 2.5" 4"

SINGLE WYTHE CONCRETE MASONRY

ead joints in brick and block walls mustbe completely filled with mortar. InBrick this is accomplished by fully but-

tering the ends of the brick before laying. InCMU the full width of each face shell shouldbe mortared. Incomplete joints may appear full on the fin-ished face of the wall, but can allow water topenetrate. Proper mortar bedding is shown tothe right for brick and block construction.

H

he tooling of mortar joints can have animpact on the weatherability of mason-ry walls. There are many varieties ofmortar joint tooling, but the only type

of mortar joint that should be used in exteriorwalls is concave or vee.The concave and vee mortar joints, when doneproperly, have the effect of compressing themortar into the joint ensuring consistency anddensity. These joints promote water to shedoff the joint without collecting.

T

o minimize cleaning, brush down the exterior during construction to elimi-nate excess mortar adhesion.Cleaning of masonry walls should be done 7 - 10

days after the walls are finished. Walls shouldbe saturated with water first. Then using achemical cleaner made for the job, clean wallswith a bucket and nylon brush and then rinsedagain with water. Sandblasting wears away thesurface of masonry and makes it much moreabsorbent. Power-washing can also do damageif done incorrectly.

T

MORTAR JOINT BEDDING

JOINT TOOLING

MASONRY ADVISORY COUNCIL 847-297-6704 masonryadvisorycouncil.org

CLEANING

WORKMANSHIP

FACE SHELLS FULLY BEDDED

VEE MORTAR JOINT

CONSEQUENCES OF AGGRESSIVE POWER WASHING

CONCAVE MORTAR JOINT

FULLY BEDDED HEAD JOINTS

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