Does anyone who uses a pressure-washer around the house or garden know
if it has a bad effect upon wood which has been treated with wood
preservative? I have a lot of horizontal and vertical wood around this
new house and garden here and I am inclined to apply a few coats of wood
preservative - as soon as the weather allows. However, after the autumn
rains and leaf-fall I expect there will be a build-up of
dirt/grime/slime, in corners particularly, and so I am wondering if
using a pressure-washer will remove a noticeable degree of the
preservative in such places . . . in which case it would be sensible not
to go buying us a pressure-washer!

Thanks.

Eddy.

Eddy Bentley wrote:
Does anyone who uses a pressure-washer around the house or garden know
if it has a bad effect upon wood which has been treated with wood
preservative? I have a lot of horizontal and vertical wood around
this new house and garden here and I am inclined to apply a few coats
of wood preservative - as soon as the weather allows. However, after
the autumn rains and leaf-fall I expect there will be a build-up of
dirt/grime/slime, in corners particularly, and so I am wondering if
using a pressure-washer will remove a noticeable degree of the
preservative in such places . . . in which case it would be sensible
not to go buying us a pressure-washer!

First of all, if the timber is presure treated e.g. Tanalised then nothing
can remove it.

If its an after applied product it will either soak into the timber or form
a coating on the surface. In the former case it won't be removed by the
pressure washer, in the latter anything loose or flakey will be removed
providing an ideal (when dry) base for recoating.

Standard practice in Germany & Denmark (the birthplace's of the pressure
washer) is to use one prior to exterior painting.


--
Dave
The Medway Handyman
www.medwayhandyman.co.uk
01634 717930
07850 597257

On 16 Aug, 11:23, Eddy Bentley
wrote:
Does anyone who uses a pressure-washer around the house or garden know
if it has a bad effect upon wood which has been treated with wood
preservative? I have a lot of horizontal and vertical wood around this
new house and garden here and I am inclined to apply a few coats of wood
preservative - as soon as the weather allows. However, after the autumn
rains and leaf-fall I expect there will be a build-up of
dirt/grime/slime, in corners particularly, and so I am wondering if
using a pressure-washer will remove a noticeable degree of the
preservative in such places . . . in which case it would be sensible not
to go buying us a pressure-washer!

Thanks.

Eddy.

Eddy,
Dave is quite right. If it is tanalised, you can do what you like but
if it is double vacuum treated with an OS process there will be
leeching from the outer surface of the wood which will happen anyway
with the weather. All you will do is increase it. If it is aquavac
double vacuum treated I THINK but am not certain that the level of
penetration of active ingredient is a bit less than with OS and so a
greater percentage of active ingredient will be removed.
If the purpose of the treatment is to preserve the wood I would
recommend you not pressure washing but after you have applied the
preservative to apply a surface coating with a water repellent. This
should protect the actual wood and act as a sacrifical layer which can
be re-applied every couple of years or so as it chalks away.
Application is easy with spray or brush. If it were my house and the
wood was a suitable timber for the application (say Scots pine) I
would carefully remove the cladding and take it as it is (cut to size)
to my nearest double vacuum treatment plant for treatment. I would
slip the operator a tenner to leave it in the bottom of the machine
for a day as he did his normal loads. At the end of the day, wrap it
in suitable protective polythene to protect yourself from the carrier
fluid smells and put it on the back of a pick up or lorry or top of a
car if suitable, let it "dry" for a couple of days and then put it all
back. Then I would paint it with Saddolins. I have done this with a
decorative garden fence 20 years ago and it is in pristine condition
with a coat needed every 3 years or so. My neighbour copied my style
of fence but neglected to do the treatment and is now on his second
fence.
I suspect this will not appeal! so if you are to retain timber in situ
which is not pressure treated and you wish to apply a preservative in
situ to the timber then I suggest that you use a combination
insecticide/fungicide suitable for the species of timber and its
porosity. I can advise if you tell me what the timber is and whether
there is much sapwood in it.
Chris