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Rot in Heavy Timber Columns

By Doug Friant on April 12, 2017
Timber Column with Stone Surround

Timber Column with Stone Surround

 

This heavy timber column looks terrific after 20 years of use, but there is a serious design problem with the stone surround. The column base is actually a stone veneer built on plywood and sealed at the top. Water was able to seep into the buildup, even after being caulked well at the top.

 

 

 

 

 

Rotten Heavy Timber Column

 

Here is an image of the same timber column after the stone surround was removed. There is a visible difference of the column condition above the stone versus below the stone.

 

 

 

 

 

 

 

 

 

Failed Caulk around a timber column.

 

Below the stone, water was able to seep in through failed caulk and checks in the wood.

 

 

 

 

 

 

 

Timber post set directly onto concrete.

 

The column was set directly on a concrete base, where water pooled with no way to get out (the shims were added in the deconstruction process):

 

 

 

 

 

Extensive rot in a timber column below a stone veneer.

 

The pooling water at the bottom, and the lack of drainage, weep holes and ventilation between the stone and the post created a soaking wet sauna – perfect conditions for rot to occur. I was able to fully insert my knife into the the rot just below the column cap.

 

 

 

 

 

 

 

 

 

At no time should water be allowed to pool around the wooden timbers. As seen in the example above, the wood column was fine above the stone surround and rotten beneath the surround, even though the column was exposed to the weather. The difference is that above the surround the wood could dry out, so there was no rot. Below the surround, the wood never had a chance to dry, and rot flourished. If a stone surround is required for the project, care needs to be taken to allow for drainage and ventilation between the column and the stone.

 

The proper solution is to place timber columns ON TOP of stone piers with a galvanized steel plate between the column and the concrete pier.  Examples of good timber post bases can be seen here.

Timber post column on top of a stone pier.

 

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