I'm interested in learning
more about lift-and-slide doors. We have trouble with water
intrusion from wind-driven rain through sliding glass doors. How
does a lift-and-slide door work? I've read that when the door
locks, it seats down in its track, compressing the weather
stripping. What happens at the head and the sides when the door
slips into its track?
A: Many of the lift-and-slide doors from makers such as
Fenevations, HH Windows and Doors, Weiland Sliding Doors &
Windows, and Zeluck use a European-style locking mechanism that
moves the door up and down vertically. Hannes Hase of HH Window
& Doors ( http://www.hhwindows.com ) compares the mechanism to
a sliding door on a minivan. "In essence, we're separating the
sliding action from the locking action," he explains.
When open, the door sits on grooved rollers that carry the door
along a track. The rollers can carry a substantial amount of
weight, so you can get some fairly large door panels — on the
order of 10 feet wide. Such a large panel with an
impact-resistant-glass unit weighs several hundred pounds, but it
rolls effortlessly without running over the sill gaskets.
When locked, the rollers retract and the door eases down,
compressing the sill gasket on each side of the track (see
illustration, right). At the same time, wedge-shaped locking pins
pull the door to one side, compressing the gaskets on each side.
The pins engage in the jamb at multiple points along the leading
edge of the locking panel, providing a very secure, tight
connection. At the top, a simple "slab gasket" rests against a stop
to seal the head, as shown.
This system can accommodate rather large panels (up to about 10 x
10 feet), and multiple units can be ganged together to create a
"wall" of glass that can be opened to the outdoors. In this case,
the opening requires a double track, but because the track has a
low profile to begin with, it's not much of an obstruction.
While the system has proved extremely reliable, Hase points to a
new type of hardware introduced less than a year ago in Europe by
Roto Frank ( http://www.rotohardware.com ). This system actually
retracts the gaskets. With this new system, the door stays at
essentially the same height at all times. The advantage may be more
even compression, plus ease of operation. You don't need the large
handle because you're not relying on that leverage to lift the
whole door panel. Hase is looking seriously at this system but
wants to see what kind of track record it has in the market
As a lift-and-slide door is locked, the rollers retract, dropping
the door, while a multipoint locking at the jamb pulls the door
into the jamb. This action seals the door on four sides against
wind-driven rain and air leakage
We've encountered mold
problems in the crawlspaces of single-family homes built on Pawleys
Island, S.C. We'd like your suggestions on how to correct
crawlspace mold and how to prevent it in new construction. The
crawlspaces are on homes that are less than five years old. The
homes have well-drained soils and perimeter drainage around a block
foundation. The floors are about five blocks from grade level, and
there are insulated HVAC ducts and plumbing running through the
crawlspace. The crawlspace floor was covered with plastic (6-inch
overlap at seams) after termite treatment. Plastic vents (101/2 x 6
inches) have been installed every 8 to 10 feet per the building
code, and the floor was insulated between the floor
It's hard to diagnose a mold problem
without inspecting it firsthand. Does the crawlspace area feel
damp? Are there signs of liquid water clinging to the poly on the
ground? Is there condensation on the cold-water pipes running
through that space? Mold needs moisture to thrive, and the only way
to correct an existing problem is to eliminate this source of
moisture. If there are no obvious sources of excess water (plumbing
leak, flood, runoff draining into crawlspace area, etc.), then the
moisture may be coming from condensation.
In a vented crawlspace in a humid climate, the vents introduce
ample humid air to the crawlspace. Added moisture comes from the
concrete block curing in the first year. In the relatively cool
crawlspace, this moisture is likely to condense on surfaces,
providing the water mold needs to grow. Unfortunately, most
"vented" crawlspaces are very slow to dry in a humid climate. While
vents are supposed to help the space dry, they rarely do unless the
vents are aligned to cross-ventilate and the house is sited to
allow good airflow. In addition, you have supply ducts running
through this space. How well are they insulated? Are they sealed
with mastic at the joints? Any leaks, or insulation less than R-6
(R-8 is much better), will further cool that space. The cooler it
is, the more likely the high humidity in the air will
What's the cure?
Ultimately, to prevent these problems in new construction, you're
going to have to convince the inspectors that there's a better way
to detail a crawlspace.
The solution in new construction, which is allowed by the
International Building Code, is to build a "conditioned" crawlspace
(see Soundings, May/June 2006; http://www.coastalcontractor.net ).
When building a conditioned crawlspace, you are bringing the
crawlspace inside the building enclosure, sealing out hot, humid
air and purposefully conditioning the air in there, just like in
the living space. A full description of this approach is available
from Building Science Corp. (
). As Joe Lstiburek and company make clear, the code does not allow
unvented crawlspaces, but it does allow conditioned crawlspaces,
and it is crucial that you (and the local inspector) understand the
The much harder solution is what to do about an existing crawlspace
with mold. That's best left to a qualified specialty contractor.
Remediating mold is awful work. The only way to get rid of it is to
physically remove it from the surfaces throughout the crawlspace.
Technically, mold-contaminated nonporous surfaces like sheet metal
or aluminum-faced fiberboard ductwork can be wiped clean with an
EPA-registered disinfectant such as Perma-Wash (
http://www.zinsser.com ), but semiporous materials like wood should
be sanded or media-blasted. Porous materials such as fibrous
insulation (or gypsum board, if there is any) must be removed and
replaced. It's critical that you seal the work area while
undergoing this work to prevent dispersing the mold spores
throughout the house above.
Here's what you don't want to do: Do not use bleach to solve a mold
problem. While it may remove the mold stain on the surface, bleach
does not remove mold spores, which can cause adverse health effects
even if they are dead. Bleach is also highly corrosive to materials
and to workers' skin and lungs. Mold must be physically removed
from contaminated materials. If mold and bacterial growth resulted
from black water or contaminated floodwater, materials also must be
disinfected with an EPA-registered disinfectant.
Over-painting will not fix the problem, either. Mold will continue
to grow as long as adequate moisture and nutrients exist, even if
it's been painted over. The correct approach is:
(1) Stop the moisture intrusion.
(2) For large areas of mold growth, establish appropriate
containment and worker and occupant protection.
(3) Dry the affected area.
(4) Decontaminate or remove damaged materials. Only an
EPA-registered disinfectant will work for decontaminating
(5) Safely dispose of any removed materials to prevent further
contamination of the surrounding areas.
Air sampling is not necessarily the best method to test for a mold
problem. Be aware of this if you are retaining a professional mold
remediator. Air sampling alone may or may not identify a serious
mold problem. In many cases where mold is growing on concealed
surfaces, such as on sheathing or drywall within wall cavities, air
sampling does not reveal elevated concentrations of mold in the
room air. There are also times when air sampling finds elevated
mold spores indoors that are higher than outdoor concentrations,
but significant mold growth is not present in the home. Because the
presence of moisture can be a reasonable predictor of a mold or
microbial problem, an effective investigation should take moisture
levels into account. — Clayton DeKorne
Do not use bleach to solve a mold problem. While it may remove the
stain, it does not remove mold spores. And bleach presents a hazard
to workers' skin and lungs.