I - 4 exterior finishes Flashcards
Building envelope
to protect building components from moisture damage, moisture can be liquid, vapour or solid state.
Exterior envelope three elements
sheathing membrane
capillary break
and exterior cladding
first and second plane of protection
First plane: exterior cladding (siding)
Second plane: building wrap (tyveck)
Capillary break
allows drainage for any water that makes it past first layer of protection and protects from pressure wicking of water. knows as rainscreen 10mm gap between building wrap and cladding.
when is rainscreen rquired?
in we climates where rain is prominent for most of the year.
Rainscreen
maintaining an effective capillary break cavity behind the exterior finish is the most important component of the rainscreen. creating space from strapping the building is good for drainage and allows siding to be placed on building.
Good practice to use pressure treated strapping.
Non moisture susceptible open mesh
large mats that can be used instead of strapping. these are fastened over the sheathing membrane.
must allow for drainage at bottom.
Drainage cavity compartments
purpose of the drainage space is to equalize pressure differentials caused by wind.
drainage spaces should be constructed with compartments that allow the pressure to equalize.
should not continue around corners or extent more then one story
Moisture barrier
consists of building paper, house wrap and peel and stick. BCBC calls is sheathing membrane and works as second plane protection. it intercepts all rain and moisture that makes it past cladding.
Sheathing paper
one or two layers depending on warranty lapped over one another and horizontal lines are lapped 4”
House wrap
comes in large rolls and will cover large ares. joints are to be sealed with tape to create continuous moisture barrier.
self-adhesive membrane (SAM)
(Peel and stick) applied where moisture leaks are anticipated. installed around base of windows and doors and base of walls.
Ridged insulation board
may be used instead of sheathing paper. all joints must be sealed tongue and groove or taped.
Liquid applied barriers (LABS)
(LABS) rolled or sprayed or trowweled on depending on product. create very small membrane on wall that is very durable. 100% water proof.
EIFS
exterior insulated finish system
Wood products for siding
Boards, sheets, shakes and shingles. western red cedar is main species used for exterior cladding.
heartwood is most commonly used. temperature can fluctuate causing 1/4” dimensional change.
DIfference between shakes and shingles
shingles are thinner.
shingles are 1/4-1/5” and shakes are thinker and can be split resawn or tapered.
Split shakes
generally last longer then shingles because the split surfaces resist weather more. nor normally used because finished surface is rough
resawn shakes
is a thick shake that is taper sawn into two shakes. each shake will have a split surface and a smooth sawn surface.
Taper sawn shakes
resembles a large shingle with both faces sawn instead of being split.
Cedar shakes No.1
are best grade of shingles that can be used for roofs and sidewalls 100% heartwood 100% clear and 100% edge grain BLUE LABLE
Cedar shakes No. 2
meet BCBC for roofing and sidewall. shingles tend to warp and twist. limited to sapwood and are RED LABLE
Cedar shakes No. 3
only aloud to use for sidewall. Black lable
Machine grooved shakes and shingles
made from number 1 cedar shingles have machine grooved to give shake look. kiln dried and have two edges cut parallel.
Lapped siding
develed siding is made from taper cut boards. they are installed horizontally and lapped to shed water. must over lapp by 1”.
Board and Batten
type os siding that can only be used vertically. usually used with rough sawn lumber. full 1x8 or 1x10 and battens are usually 2” wide (cottage siding)
channel siding (TNG)
can be used vertically or horizontally. overlap is 1/2”.
Drawbacks of lumber siding
- obtaining quality lumber is difficult and expensive
- wood siding requires maintenance (paint or stain)
- if low quality wood is used knots may call out or wood will split
- takes longer to install
- more prone to rot
Panel-type wood siding
sheets of plywood, heardboard, or OSB and wafer board can be used as exterior finishes. face of plywood has shallow grooves to at 8” to resemble vertical boards. joints in panels and nailing can be hidden by grooves.
Vinyl and aluminum siding
popular because cheep and easy. it produces a capillary break at the bottom of each sheet that have small drainage holes.
vinyl comes is 12 foot sheets. and can change 5/8 depending on season *never butt up to trim or mouldings. must be hung on nails.
stucco
two different types of stucco
- synthetic (acrylic) stucco
- cement stucco
Synthetic stucco (acrylic)
mix of glues , fibres and acrylics applied in two coats. overall thickness is much less then cement stucco.
used to finish EIFS and used largely on commercial construction.
Cement stucco
made from sand cement and lime and water and applies in three coats
provides hards dense water resistance finish. must be minimum of 3/8 thick.
Stucco wire
installed over sheathing. wire has bumps (self furring devices) that space wire away from wall.
expanded metal lath
is made from sheets of steel that have been punched with slits. the sheets are pulled or expanded from a dense surface of fine holes. expanded metal lath is used for extra reinforcement at corners and overhead situations. stucco sticks to this way better then wire mesh
Stucco mixes.
cement stucco is made from sand cement, lime and water. sand must be clean. lime is used to make solution workable and help stick to overhead surfaces.
Proportions of stucco
1 part portland cement
1/4 part lime
3 1/2 parts sand
this will give strong stucco mix add water to make workable only.
application of stucco
- the scratch coat made with plain washed sand and grey in color. scratching with a broom or rake roughens up surface min 6mm thick
- second coat called brown coat. 10% more lime and sand then first coat. used to level surface of wall min 6mm thick
- white sand colouring. finish texture coat provides look for stucco Min 3mm thick
Brick veneer
Veneer is a thin layer of material on top of another material. veneer plywood has thin layers of wood placed one on top of the other. brick veneer construction id s thin layer of brick over other construction.
how big is space supposed to be behind brick vaneer to allow moisture to evaporate.
25mm
cultured stone
is a concrete product that looks like real stone but is only a quarter the thickness. wall sheathing is protected with two layers of a waterproof barrier, and then metal lath is applied. cultured stone is then fixed to lath with mortar.
Sheet metal finishes
ribbed or crimped metal panels. finished with bake enamel or vinyl plastic. aluminum, copper and stainless steel siding materials are available but not often used.
fibre cement siding
made from combo of sand cement and cellulose fibre.
durable, fire resistant and requires little maintenance. james hardie was first manufacturer.
asphalt shingle siding
BCBC allows the use of these to be used as siding. same shingle used for roofs.
overcladding
process used to modernize older high rise buildings. many older high-risers, are not energy efficient and overcladding often uses metal panellized metal that adds insulation.
Exterior casings
doors and windows trimmed with exterior casings. helps seal the connection between exterior finish and window or door.
water table
overlapping the trim materials is very important to prevent rain water from entering the building. water table is used at the base of a wall to make a horizontal join to the foundation or accent board.
Drip cap
same shape as water table moulding BUT its used over doors and windows to form sloping edge to deflect rainwater away from building. metal flashing often replaces drip cap
Flashing
required over exposed openings in exterior walls and horizontal joints in the finish materials that are not overlapped by 25mm
may not need flashing over windows and doors that are protected by roof protection.
how far must flashing extend up wall
minimum 2 “
need flashing ontop of window or door if…
- if distance from underside of soffit to window is more then 1/4th of the projection then it needs flashing.
EX: projection is 24”. distance from the underside of soffit to the window is 8 1/2” flashing must be installed because 1/4th of 24 is 6” and 8.5” is greater then 6
Screened vents
used in wooden soffit
Vinyl trim starter strip
used to attach bottom of the first siding board to wall
under sill (vinyl trim)
used to finish off cut edges of the vinyl siding at the underside of windows or soffits
J trim (vinyl trim)
used to finish sides and tops of openings
Lag screws
used n sheet metal siding. fitted with neoprene washers to make water tight.
nails
must be resistant to rusting. galvanized aluminum or stainless steel nailed are used for exterior work.
galvanized nails
hot dipped, designed for exterior use are resistant to rust and corrosion. strong holding power
electroplated nails
designed for use where not exposed to weather, the electro plated nail also resists corrosion and rust. not as strong holding power