|
|
|
Summary: Summary- It is always important to remember that footings or piers required in some decks are supposed to be built below the frost line. This prevents the piers from swaying up and down due to harsh winds, and it is also suggested to use steel reinforcements to prevent cracks in the piers.
Question- I am planning to build a deck and am wondering as to how far should the ground be dug for the wooden deck post? As per my knowledge, it should reach out to the frost/freeze line; can you let me know what these lines are, and where are these located in the decks? Apart from that, please also let me know if I need steel for the piers and what should be the diameter of the hole?
Answer- The frost or the freeze lines are regarded as the levels up to which the soil freezes in general or has frozen up to that level in the past. It is important to ensure that the building foundations reach the specified level. Apart from some few dry places, the soils possess water content in them, which is expected to expand around 9%, when it freezes. The pressure hence cause id very powerful and is capable of moving deck structures, foundations of the house and concrete slabs like an Olympic weight lifter who picks up his bag while moving out of the locker room.
As such, these levels cannot be determined on the base of countries, as there are vast differences in the climatic conditions of different places. For instance in case of Southern Florida, this level is under a foot, whereas in Minnesota it may it is almost six feet. You can consider visiting the local building department for determining the level in your area. The professionals involved in this de vast department perform inspections everyday to make sure that the hole is deep enough and the bottom soil of the foundation is strong enough to hold the vast infrastructure.
Similarly, the diameter of the holes for the piers are not determined on one’s own will. And as stated above you will have to contact the local authorities responsible for this. You can even consider hiring a structural engineer or an architect for this purpose. The decks tend to exert a lot of pressure on the underground soil on which they are built. If the entire weight of the deck is calculated including the furniture and the approximate weight of the people over the deck, it will present you with an astonishing number of over twelve thousand pounds.
In case your deck is designed like most of the other decks with a rim joist and a couple of deck posts, secured to the house, each of these posts would be responsible to bear up to 25% of the entire weight over the deck, and the soil beneath would be expected to be strong enough to hold over three thousand pounds comfortably.
In case of the diameter of the hole in such cases, it may vary from 12”-24”. The holes with larger diameters would be spreading the weight over more of the area of the soil in comparison to the holes with smaller diameter. The shape of the hole is another factor to be considered. In general it has been observed that the shape of the holes for the posts and piers resembles an ice cream cone, in which the bottom is quite smaller than the hole’s top.
The important thing is that this shape should actually be vice versa, which means that the lower end hole should be around 25% more than the top area of the hole, as the frost gathers in the holes, it forces the pier upwards, whereas if the shape is appropriate like a nail or a screw, the base of the soil would have to be torn to lift the pier upward, which is next to impossible, hence providing more safety to the pier. If the diameter is large, it also acts beneficial in spreading the load over the larger area of the soil.
Including a few pieces of vertical steel reinforcements is highly recommended during the period when the concrete is being poured in the pier hole. These are cheap products but have been really efficient in strengthening the piers which are over thirty inches tall. The tall concrete piers are also affected by the sideways or lateral pressure of the soil, which moves downhill with time. In such cases the steel pieces would be a great support and will be helpful in preventing the pier from breaking down into two pieces because of the pressure.
In case you plan to build the wooden pier in the exact centre of the pier, you are always advised to approach a qualified professional, if you are not a surveyor yourself, with experience in building decks. The process otherwise is very simple and you can conveniently center the posts if you have outlined the deck and have it marked in the air for positioning of the posts.
You are always suggested to begin with the rim joist being attached to the house. You can make use of joist hangers to attach the joist’s ends of the deck to the rim. Remember to support the other end of the joist at equal level with the help of a piece of timber. This should be followed by nailing the external joist to the other two ends of the joists which are extending from the house. This would complete the outlining of the deck. Also remember to make sure that the outlined deck is in proper levels from all places.
After completing the outline deck, you can consider dropping a bob from all corners, which will help you determine the exact positions of the piers.
© Copyright www.diystuff.com
Top of Page
|
|
|
|
