increasing fence height

[cookerooby]

I have an approximately 1 metre high closeboard fence that has 2 mortised arris rails into 1 metre high concrete posts that are approximately 3 metres apart. The featherboards run vertically and are not actually feathered but are simply planks nailed onto arris next to each other (not overlapping) they have a nominal width of 90mm. The top has no capping strip and the bottom has no gravel board, rather, from what I can see, a kind of concrete plinth has been formed for planks to be cut to. One run of fence has arris facing into our garden and the opposite run has planks facing our garden. House is on market and privacy in back garden will be an issue to potential buyers. What would be the best way to increase height of fence with the least disturbance to it? I suspect trellis maybe one answer but this would have to be at least 800mm and with the the concrete posts being only 1m high and 3m apart am worried how I can adequately fix it. As mentioned house is up for sale so an economically sound answer would be appreciated! Hope the doctor can help.

Cheers.

[thedoctor]

There is little you can do other than fix a timber vertically to the concrete posts to extend the posts. Anything you fix to extend the height, as you rightly sat about a trellis, will need to be supported and the only way to do this is to extend the post. Concrete posts are not easy to fix to but it can be done if you see our fixing to masonry project and start the hole with a small drill bit and then enlarge it to suit the type of plug and screw you are using.