Wooden Fences- Pressure treated retention ratings

When constructing a wooden fence, it is important to use a lumber that is rated properly for its use. When using southern yellow pine, the common wood in the Raleigh/Durham area, it is crucial that it is not only pressure treated, but also rated properly. This is referred to as the retention rating. The retention rating, simply put, is the amount of chemical the lumber retains after it is pressure treated. Lumber that is rated for ground contact has a retention rating of .40. Lumber that is rated for above ground use has a retention rating of .25, and marine lumber, lumber used at the coast and in boat areanas, has a retention rating of 2.0!

When purchasing fence posts, make sure they are rated for ground contact. Most 4×4 and 6×6 posts are rated for ground contact.  If the lumber is not rated for ground contact, the wood will decay when placed in the ground resulting in a fence with a short life. Although landscape timbers are less expensive than 4×4 posts, most landscape timbers are not rated for ground contact. You can read the back of the tag on the lumber and it will tell you the retention rating. The retention rating for in ground posts is very important for a long lasting fence. With that being said, there is no reason for overkill. Buying marine grade lumber with a 2.0 retention rating for a normal fence will not improve the life of the fence. It will only cost you more money and you will get the same results!

Pickets and runners also need to be pressure treated, but not at the same retention rating since they do not contact the ground. A retention rating of .25 is the common rating for this lumber. This rating protects the lumber from rain, washing the fence, and the normal elements, except for the sun. It is good practice to place pickets 1″ off the ground to allow for water drainage and to avoid constant ground contact. You can place pickets directly on the ground, but you may see swelling and splitting at the bottom of the picket over time due to constant ground contact. This also depends on the yard and area the fence is being installed on. If the fence is in an area of the yard where rain water drains, or the yard is naturally damp, the pickets will deteriorate more quickly if placed directly on the ground. This is a good subject to discuss with your fence contractor.

One element I have found to be a constant problem for wooden fencing is the sun. The extreme heat and exposure causes lumber to warp, bow, split, and grey. One way to protect form the sun is to stain the fence. You can use a clear stain or a colored stain. Either way, make sure the stain contains a UV protectant and a water sealer. Most stains can be applied with a pump sprayer and the job is fairly easy. Carolina Custom Fences does offer this service, but it is a job that can be easily accomplished by a home owner with a few hours to spare!

Thanks for reading! Please feel free to comment with any questions or topics you would like to see!

Scott