Hello. The windows in my Mom's house were just replaced. Apparently they had
to move the windows about 1/4" forward from where the previous windows were
(according to the person who installed it, this was necessary to get a good
seal so air couldn't get it - apparently the previous windows had not been
installed correctly and didn't have a good seal) so on each window there's
now about 0.25" space on the window sill (between the sill and the window).
I asked the window person what to do about the void. He said to fill it with
a piece of wood so I'm attempting to do that. The other alternative I guess
is to use wood putty or bondo to fill in the void.
I measured the void on one window to see what size of wood I would need.
Upon doing so, I found out the distance between the window and edge of the
sill (the depth measurement) varies significantly as you go from one end of
the window to the other so that one piece of wood with the same
cross-sectional area would not fit well.
Solving this is a headscratcher for me. The space seems too big to fill it
all with wood putty or bondo (the size of the void on each window is roughly
35" wide, 1" high, and 0.25" deep so it would be a lot of wood putty or
I'm guessing the thing to do is fill each void with several pieces of wood,
each piece having a different depth (since the depth of the void changes as
you go from one end of the window to the other) and glue them in somehow (or
nail them in with small nails and top it off with wood putty) and then fill
around those pieces of wood with wood putty or bondo. And somehow make all
this look like a continuation of the existing window sill after the sill and
void are painted.
I'd appreciate any ideas on how to solve this problem. I'd also appreciate
responses from people who have used a lot of wood putty (or bondo or
whatever) to fill a large void like what I have and how it worked out.
My reply would be to the installer "you're not done yet".
The answer on the use of filler for such a fix is it's possible but not
a real good solution. Really need somebody to do it that has the
facility to fit pieces in. It's not too difficult but depends on what
one has for tools and skills???
Alternatively, the other solution is to replace the sills or remove them
and add the width necessary and then trim to fit when replacing.
IMO, in order for you to say that was indeed the case, you would have to
know with certainty what kind of window was put in.
It is not unusual, for instance, for a modern vinyl window to be thinner
behind the nailing fin than an old window, thereby possibly leaving a gap
between the new window and the old sill when installed, as the OP reported.
In addition, the age of the house could be a factor. Thicker because framing
lumber was a different dimension, 2 x 6 exterior walls instead of 2 x 4,
That said, the "seal against the building" does seem to be a peculiar
remark, although not impossible ... it would certainly make me want to ask
some questions as well as take a close look at things like flashing and
caulking with a practiced eye.
Unfortunately, as I builder, I rarely see a window company around here
include redoing sills in the price of new windows unless it is specified in
the contract at extra cost. That may just be a regional thing, however,
since this is hurricane country and there are a lot of windows replaced,
that could explain the practice, or lack thereof.
Replacing/redoing sills, means a trim carpenter, AND a painter, perhaps
having to match paint, in many cases.
AAMOF, when called two weeks ago about a similar issue, I sent my trim
carpenter and painter, as a courtesy, to a house completed two years ago to
touchup the sills and casing on two new "sound proof" windows that the
homeowner, being a light sleeper, replaced in the bedroom to keep out
While I suggested OP tell the window company rep to "fix it", I'm sure
their contract is written to allow them to claim it's not in the scope
That said, I think it sucks weenies as a practice as one can be sure the
sales rep didn't point out the likely or possible problem or that it
wouldn't be covered when making the sale and it certainly is a detail I
think virtually any homeowner would expect to be "made right" as part of
an installation simply as being part of the "workmanlike manner" clause.
Leaving a noticeable gap when done just isn't up to snuff imo.
$0.02, ymmv, etc., ...
I'm just going by the original poster's first paragraph. If the gap was
caused by window design then the installer should call it what it is and
not blame the previous installation.
If the previous installation wasn't tight enough, that's the one that would
leave a gap, not the new tight one. The logic of the installer's excuse is
Um, a little quick math here...
2x6 vs 2x4 does not yield a 1/4" gap but more like 2".
Maybe good old fashioned 2x4s that really measured ~2x4 instead of 1.5x3.5
is a better guess.
But again, if that's the reason, the installer should have explained it that
way, not blaming the previous installation.
I guess that assumes the installer even knew what he was looking at.
I've seen 2x4's go from 3-3/4x1-3/4 to 3-1/2x1-1/2 and lived in a
1920's farmhouse where the 2x4's measured 2"x4".
Many (if not most or all) of the modern clad windows are thinner than
the pure wood frame windows.
I'm sure that any of the above differences could have caused the
Many years ago I had a sideline business selling and installing replacement
windows. These were pre-made units that slipped in where the old sashes
were. There is a stop on the outside for the old sash. We just ran a bead
of caulk and put the new unit in place against it, drove a few screws, put
the trim back and it was done. If, for some reason, the sash was thicker
than normal, there would be a gap at the sill. There was, normally, no
reason to touch the sill. If there was a gap, we carried some prepainted
wood trim to put in place.
At the time, we were paying $35 for a window unit and charging $55
installed. That was $20 every half hour! Big bucks in the 1960's.
Sounds like a perfect application for a piece of 1/2" "trim" or quarter
round molding, painted the same color as the "sill".
What I'm not certain of is that your terms, "sill", "width", "height",
"depth" are standard definitions, which could make any answer no workable.
Can you link to a picture?
Partly a question of personal taste. Some might suggest attaching a 1/4 round
or concave moulding over the top, that certainly works.
I personally would varnish/paint the window down into the gap (to seal the wood
against any creeping moisture) and then put a thick bead of (tinted?) silicone
into the gap and shape it concave making sure it bonds to both sides.
Silicone should accomodate temperature-related movement of window and sill
without cracking. Could even put enamel paint over the top of most products
after the job's cured.
firstname dot lastname at gmail fullstop com
I've got to side witht he fellow who asked for a PICTURE.
But, then, the prices involved are likely rectilinear when first
constructed. So, don't worry about filling the gap with pieces that
match the gap, but that match one of the existing bits (Sil or
whatever), then, putty/seal the remaining cap.
THere's a product called Water Putty - forget - but it comes in a red
and whilte (and maybe a little yellow) cardboard "can." You mix it
with water and you get ROCK HARD (water) PUTTY. It does shrink some -
but it does dry hard and faxt. It is "sand able" and (relatively)
cheap. http://www.waterputty.com/ email@example.com "will withstand
weather if kept painted" "Durham's is meant to fill voids"
Did your windowmoron install flashing to redirect the water at the top to
the ground rather than the gap?
If not, that's your first order of business. Under the siding or whatever
forms the skin of the house, then at a slant past the gap and window top.
Commercial products are available.
If the windows are secure in their openings, I'd hit the gaps elsewhere with
the low-expansion poly foam aerosols, trim, and caulk with latex. The
Durham's isn't flexible enough, though a wonderful product I've used for
years in woodworking.
FYI...the OP posted the same question in a.h.r, Nor cross-posted, so
replies here and there, don't show up there and here. This was my
reply in a.h.r, based on my recent window replacement project:
If I understand your question correctly, I had the same problem when
replaced my windows. It doesn't mean that the old windows weren't
installed correctly, it means that the new windows are "thinner" than
the old ones, say 3.25 inches deep instead of 3.5. When the new
windows are pushed back against the exterior stops, an interior gap
As Dan suggested - backer rod and caulk will solve the problem. See
this site for info on backer rod:
Don't try the borgs to purchase - none of my local home centers
carried it nor did anyone in the paint/caulk department know what it
was. I went to a contractor supply house and paid between .05 and .
per foot depending on the thickness. The supply houses sell it in
by the foot as opposed to packaged in pre-cut lengths. It's much
cheaper than way. I used 1/4" or 3/8" around all 4 sides of my
before caulking the interior. There'e really no good way to caulk
gaps without it...that's what it's made for.
My concern is that if the contractor did not seal the inside of the
window along the sill, what else didn't he do? By sealing both the
exterior and interior edges of the entire window, you create the
desired dead air space.
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