Rod Serling in the Twilight Zone would use the phrase “submitted for your approval..” and then go on to describe the latest nightmare scenario. I have my own example to submit, captured in the photograph below.
A hardwood deck in Cambridge, built flush to the existing pine water table and adjoining riser, created a perfect environment for this fungal growth. We see this all the time unfortunately; carpentry that looks tight and snug upon completion but results in premature failure. Two issues here; pine is an atrocious material for a water table, especially retained moisture is guaranteed. Old growth pine, which is no longer available, was a durable wood and well suited to exterior use; contemporary pine should only be used inside and for making pencils…..
The second issue is the decision to place the hardwood planks snug up against the water table. In an ideal environment this might work, but not in New England. The combination of leaf litter and year round moisture created a virtual petri dish in this corner. The plank should have been placed further away from the water table and riser, allowing more opportunity for air flow and drying.
We replaced the riser and watertable with Azek – not our favorite material from a carbon footprint perspective by any means, but one that will certainly last as long as the house.