What is the maximum acceptable moisture content percentage in construction timber for a stick-built house?
The reason for the question is that we replaced the roof a few years ago, tongue and groove + felt + tile imitation (metal), and the tongue and groove is now black-spotted. This is said to be because the tongue and groove was not dry when it was installed. However, the weather was perfect in July when we did the job, and the timber was well covered at night, so the moisture would originate from the "manufacturing," i.e., it was not dry enough from the sawmill.
The reason for the question is that we replaced the roof a few years ago, tongue and groove + felt + tile imitation (metal), and the tongue and groove is now black-spotted. This is said to be because the tongue and groove was not dry when it was installed. However, the weather was perfect in July when we did the job, and the timber was well covered at night, so the moisture would originate from the "manufacturing," i.e., it was not dry enough from the sawmill.
Byggnadsingenjör
· Skåne
· 1 458 posts
Hello jakim!
If I'm not mistaken, the moisture content of construction timber should be below 17%.
The moisture content is affected as soon as the timber leaves the kiln. In winter, the air humidity is lower, while in summer it's higher. Therefore, the duration the timber is stored at the worksite matters.
From your description, however, I don't believe that the moisture content of the timber is the sole reason for the mold infestation. If I understand correctly, the roof decking is visible from the inside of a cold attic. It is very important that these attics are properly ventilated. Otherwise, they suffer from the same problems as crawl spaces during the summer months, i.e., warm, humid air condenses inside the attic.
Make sure the roof is properly ventilated, and you should be able to resolve the issues.
If I'm not mistaken, the moisture content of construction timber should be below 17%.
The moisture content is affected as soon as the timber leaves the kiln. In winter, the air humidity is lower, while in summer it's higher. Therefore, the duration the timber is stored at the worksite matters.
From your description, however, I don't believe that the moisture content of the timber is the sole reason for the mold infestation. If I understand correctly, the roof decking is visible from the inside of a cold attic. It is very important that these attics are properly ventilated. Otherwise, they suffer from the same problems as crawl spaces during the summer months, i.e., warm, humid air condenses inside the attic.
Make sure the roof is properly ventilated, and you should be able to resolve the issues.