Unwarping wood
 

On Tue, 06 May 2003 07:39:55 GMT, Middleton Design Associates
wrote:

I have some remade skirting boards (old victorian/edwardian style) and two
thirds is flat with the top third machined into a decorative shape. The
thinner bit is warping towards the missing material. Is there a technique to
ease it back - such as wetting one side or using a hairdryer or something.
Or will it return over time? This is the bit that will (not) be flush with
the wall at the top, so should one fill the gap. All thoughts gratefully
received.

You can probably pull this into a reasonably flat state while fixing it
to the wall as follows:

Drill and rawl-plug a row of, say, 2" no. 10 countersink screws into the
wall where the convex rear face of the board is maximally warped (i.e.
about half-way up the board height). Before fitting the board, screw
these screws in until the top of the head is where you want the rear
board face to lie. Get them all to the same horizontal line (unless the
wall is curved!) by running a string along the row and adjust till they
all just touch it. The heads should also lie on a vertical level with
the finished wall surface. Note that these screws do not go THROUGH the
board!!

The next step is to fix the board with pairs of screws, one above and
one below each of the above screws. Then you should be able to pull the
board flat as you screw it to the wall with these screws, bearing
against the first row. These screws need to be fairly substantial and
properly rawl-plugged into the wall, again 2" no. 10 countersinks should
do.

Be careful as there are a few "gotchas". The main one is the problem of
rawl-plugging the screws behind the board so you can pick them up later
with the screws. The only way to do this is to drill pilot holes through
the board at all locations, then offer up the board to the wall and pass
a masonry drill of the same diameter through these pilots to 'pilot' the
brickwork behind, then remove the board and finish off the holes to
final rawl-plug size. You can countersink the board at this time. Now
when you finally fix the board the screws should find their rawl-plugs
OK.

Another "gotcha" is that you may find some screws falling into voids
between the bricks. You need to check that the intended screw positions
do not fall into these. Also you have to be careful not to put the top
screws into too thin a section or you may split the board.

If the board is warped the other way (convex) the procedure is similar,
but you put two rows of supporting screws behind the board and fix it
with one row along the centre line. In either case there are 3 screws at
each fixing point.

Its rather complex to achieve, but this method results in a perfectly
straight and vertically fixed board. The downside is that you have to
fill over the screw heads before decorating. To locate the screws for
subsequent board removal - use an electronic cable/batten/pipe detector.

--
Phil Addison
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