CAULKING AND WEATHERIZATION
Autumn may be a confusing time of year if you need to seal up your house for the coming
winter. Where do you use caulking? Weatherstripping? Glazing? How are they different?
Don't feel alone in your confusion. There are a lot of products available, and the differences
among them, where you use them, and how you use them would likely confuse many home
builders as well. Let's see if we can make some sense of them. Refer to the chart on page 3 for a
guide to the different products and some tips regarding their use.
First, you need to keep in mind just what you are trying to achieve – that is, to seal the exterior
of your house to keep out water and cold air. The main thing to remember when you are sealing
two different types of materials together is that each material will expand and contract at its own
rate. So, you need a sealant that will flex with the seasons and bond to the specific surface(s) you
Glazing putty is used to seal glass to the wood sash frame. If the putty is cracked or missing,
cold air will bleed around the glass panel. It’s easier to work with glazing putty during warm
weather, but you can work indoors if it’s cold outside. (See separate handout on “Window Glazing” Spray foam is the best product for filling a hole or crack larger than
5/8th of an inch. Modern spray foam sealants not only expand to fill up
the hole, but also have insulating value. They will bond very well to
just about any surface – including your hands (so wear gloves when
you use them!) The foam can be trimmed easily when hardened, but
will need to be painted if exposed to daylight. Plan to use the spray
foam all at one time, as unused foam will harden in the can.
Caulking (which usually comes in a cartridge-type container, but is
occasionally found in squeeze tubes,) is used to fill long, narrow gaps
between similar or dissimilar materials. It comes in a variety of colors
and is rated by the number of years it will stay flexible. You shouldn’t
cut costs and get a less expensive caulk, because you'll end up doing
the job again in a year or two. Caulks with a polyurethane or acrylic-
silicone base are the best all-around caulks available. Many now have
a rated life expectancy (the period of time they will bond and stay
Where to Seal Your House: Exterior
Sealing exterior gaps and seams is important home
maintenance. It will reduce drafts, dirt, and moisture
infiltration into the house walls and contribute to lower
heating and cooling costs. You can use caulk backer rod, a kind of Styrofoam rope (right) to fill gaps, so that
you won’t need to use as much caulk to close the opening.
You may need to use a combination of products to seal your house for the winter. Check the
following areas on the outside of your house for places where cold air can enter:
• Joints between eaves and gable molding
• Where the window trim (casings) and siding (or masonry) meet
• Where the siding meets the foundation
• Joints between masonry or concrete elements (steps, porches, etc.) and the main part
• Where wires, cables, conduit, and garden hose spigots pass through the siding.
Where to Seal Your House: Interior
Sealing each room on the inside is the only way to prevent blasts of air from entering. Even
with sidewall insulation, a lot of air will leak into a house. A good caulking job will increase the
comfort of your home considerably. You may find gaps so wide that caulk backer rod will be
required. You can tape a piece of tissue or plastic wrap to a pencil and check the following
• Outlet and switchboxes on exterior walls: Gaskets for outlet and switch
cover plates can help prevent air leakage through the walls. If there is a
gap between the box and the wall, fill the gap with caulk (It’s a good idea
to turn off electricity to the box to prevent a shock hazard.)
How to Caulk:
The best time to caulk an exterior joint is in the spring or fall, since extreme heat or cold may
affect curing. A standard 10.5-oz. cartridge will usually produce enough caulk to seal two or
three windows or doors, if the gap is not too large.
Before applying the caulk, make sure the surface is completely dry. Use a putty knife or old
screwdriver to remove any dirt or loose debris, paint build-up, or old caulk from the area; you
may need to use a solvent. If you are using a caulking gun, cut off the tip of the cartridge, pierce
the foil seal, pull the handle back to its furthest extent and insert the cartridge. As you press the
trigger repeatedly to apply the bead, pressure is applied to the end of the cartridge to expel the
caulk. When you want to stop applying the caulk, turn the handle 180° to relieve the pressure. Drawing a good bead of caulk will take some practice. Make sure the caulk overlaps both sides
of the gap for a tight seal. You can smooth the bead with a wet finger, with a damp sponge or lint-
free rag, or with a special tool made for that purpose. Weatherstripping Doors: A quarter-inch gap under a door is equivalent to a
four-inch diameter hole in a wall. So, you should always
make the door as airtight as possible – not only at the
bottom, but all the way around. There are a variety of
systems you can use to seal around your door. The old-
fashioned method of door weatherstripping, with a metal channel and metal strip that fits into
it, is still the most effective. (A full-service lumber-yard or store specializing in doors and
accessories are your best bets for locating this type of weatherstripping.) While some of the
new plastic systems may not work as well, they will nevertheless reduce air intrusion.
Replacement doorstops with a spongy rubber-bulb weatherstripping will help seal a wood
exterior door. They are nailed to the doorjamb and will work on a door that is slightly warped.
Pre-hung steel doors have a thermal break and magnetic weatherstripping (much like the door
seal of a refrigerator) that work well to seal out the cold. Remember that, with use, the strip along
the door bottom in many systems can wear away, so you will need to check it periodically and
replace it when necessary. You may also want to look for a system that will allow you to adjust
the bottom weatherstripping to keep it snug as seasons change.
There are literally hundreds of ways to seal up your home. The chart below explains some of the
products available and where they should be used. (See also our separate handout on PRODUCT NAME APPLICATION & USE COMMENTS _________
the jambs out of position; use “regular
fibers (i.e., rotted window sills) to form
_________ 2011, Home Repair Resource Center, 2520 Noble Rd., Cleveland Hts., OH 44121 (phone: 216-381-9560)
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