What is pier and beam foundation?
Pier and beam foundation is that foundation that is made up of the combination of the pier and beams. Piers are attached with a beam and go below the soil to make the structure stable. It is also called post and beam foundation.
Piers helps to join all the beams above it and transfer all the loads on the beam to the soil. In ancient times pier beam foundation was popular due to its raised structure above the ground.
This foundation helps the houses from entering animals directly into it and also protects the room of houses from rainwater.
Nowadays due to advance technology, different materials are used to construct such residential as well as commercial buildings. One of them is concrete technology. It can be made waterproof as well as strong enough to resist anybody to enter a concrete restricted area.
Concrete technology has become more popular in modern days due to its durability, strong and monolithic properties.
How to build a pier and beam foundation?
Pier and beam foundations should be built and installed very carefully. If any of the piers become tilted then it may cause uneven settlement of foundation and cause cracks in the beam.
There are few steps to build a pier and beam foundations are given below.
1) First of all dig the ground up to the best depth and compact the base of the foundation.
2) After that place the concrete to make the footing stable.
3) Now, sink the pier and make it tight with the help of shuttering or scaffolding.
4) Join all the piers with the help of a joist to tight it. It should not be moved till the joints become stable to bear the load.
Pier and beam foundation spacing
The crawl space of the pier and beam has about 18 inches to 22 inches from the home. This space can be used for electrical wiring as well as plumbing for water and gas.
Pier and Beam foundation repair cost
The cost to repair the pier and beam foundation depends upon the place to place. The cost is measured in square feet of the area of pier and beam. Generally, on average the cost is about $9 per square foot.
After you constructed a house, it may have to repair after some time. The repair cost is very expensive as it needs some special equipment to lift and remodel the pier and beam structure.
The average repair cost is about $11 t0 $13. But it also depends on the experience and branding of the repairing company.
Advantages and Disadvantages of Pier and Beam foundation
- It can be moved from one place to another as it has not permanently attached with the ground.
- It can be repaired by lifting with the help of hydraulic machine easily.
- Pier and Beam foundation made of wood can be broken into several parts to carry in vehicles and easily transported from one place to another.
- It prevent superstructure from seepage and moisturizing.
- The models and appearance of foundation can be redecorated easily.
- Electricity and water pipes are easy to install below the foundation of house.
- There may be the home of insect between the spacing of the home, where we place wiring and plumbing.
- Pier and Beam foundation may decay easily if it is constructed with the help of wood, steel etc.
- It is not strong enough to bear high seismic loads.
- There may be problem of lateral movement of structure due to heavy load moving beside the structure.
- It can not bear heavy load like mat or raft foundation.
Pier and beam foundation problems
- Some time due to movement of heavy load beside the foundation there may be shifting of beam and sagging or hogging of floor below it.
- If the piers are not not adjusted vertically, then there may be consolidation below the tilted piers which may cause cracks in beam and floor above it.
- Concrete are brittle in nature which may crack and looses the footong of pier. It makes uneven settling of piers and weaken the beam to bear load on it.
- Defect in wood of beam may suddenly cause collapse of due to load on it.
Solution to get ride of Pier and beam foundation problems
- The base of the pier should be compacted well with help of heavy load.
- The connection between beam and pier should be made stronger such that it do not move due to general lateral loads.
- Tilted pier should be made vertical as soon as possible.
- The beam which are defected naturally or artificially should be removed immediately.
- Uneven loading on the beam should be avoided.
- Beam and pier should be protected from moisture as far as possible.
Where should we prefere pier and beam foundation?
- It can be preferred where the level of land below the structure are uneven
- Where the load bearing capacity of soil is low
- Where there is chance of moisture and flooding due to rain
- It is preferred where land become dry and wet in regular interval of time.
Steps for Pier and beam foundation design
The design of this foundation is to calculate the best dimension of the pier and beam. The length, width, and depth should be safely designed. The following points should be followed according to the Country code of design and analysis.
1) Calculate the area of the footing
Area of footing = (Load/Safe bearing capacity of soil)
2) Calculate the total load
Load = Service load + Self-weight of footing
3) Calculate the net earth pressure acting upward to footing (BCS) is calculated.
BSC = (Factored Load/Area of footing)
4) Dead load, live load and wind load, and pore water pressure should be considered.
5) Maximum bending moment should be calculated.
6) Depth of footing is calculated
7) Calculation of reinforcement should be done
8) Finally the design should be checked for one-way shear, two-way shear, moment, and development length.
9) Sketch the drawing with neat and clean paper.
I hope this article remains helpful for you.
Happy Learning – Civil Concept