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Repairing Raised Deck With Pergola With Damp Damage

Postby Roysy » Tue Sep 20, 2016 2:48 pm

Pergola intact.jpg
Pergola intact.jpg (86.46 KiB) Viewed 732 times

I have recently moved to the Welsh Borders, a lot wetter than my previous location in Suffolk. I have a very steep garden and a deck with pergola has been built at the top. Although a lovely addition, since this photo the hardcore underneath has clearly showed movement and has pushed out the sleepers at the front. I have started to remove the loose sleepers and note the hardcore underneath is a damp mess and the damp atmosphere is affecting the timbers which are covered with mould. Fortunately the underlying wood does still feel sound. The sleepers themselves have also rotted significantly highlighting the significant damp.

I am a little puzzled why the underneath would be packed with hardcore which perhaps is ignorance on my part. I am more inclined to remove the damp hardcore and rotten sleepers. Treat all the underlying wood and replace the front with removable slats with gaps between for decorative purpose. By doing so, damp could be minimised as air circulation will be encouraged and each year I can check for any repair work on the structure and keep it all well treated.

I have provided some pictures below which may be easier for you to visualise the problem.

I would appreciate others opinions on the role of the hardcore.
Hardcore under pergola.jpg
This shows the damp mess underneath
Underneath Pergola.jpg
This is underneath which also shows the mould growth
Front of pergola.jpg
This is with the some of the sleepers removed
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Simply Build It

Postby neil-the-handyman » Mon Sep 26, 2016 10:51 pm

You could bridge the gap between the hardcore and the sleepers using soakaway crates wrapped in weed suppressant matting this would allow air flow in conjunction with your other observations and be man enough for the job.
The only other point I can think of at present is to ensure that the posts aren't sat with soil above the concrete. Always dome the cement around then to reduce exposure to all the microbes.

Hope this helps,
Kind regards,

Neil the Oxford handyman
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