Screw piles are steel pipes ending in a blade and a pointed tip. They are screwed into the ground like screws.
An important part of the pile is the tip, as it performs several functions at once:
- is the supporting part of the pile;
- transfers load to the ground;
- prevents piles from being forced out of frozen ground during winter heaving.
The problem from the last point is most often encountered in the construction of light wooden structures, using piles of small length. The only way to avoid swelling soils is to deepen the foundation of the house below the frost line in the construction region.
Where are screw piles used?
Prefabricated inexpensive foundations for light frame buildings - this is where screw piles are used, the pros and cons of which we will consider a little lower, but for now let's figure out their sizes.
Under which house which piles?
For individual construction, the following types of piles are most often used: CB89x250, CB108x300, CB133x350. This abbreviation is deciphered as a screw pile with a shaft diameter of 89 (108, 133) and a helical blade diameter of 250 (300, 350). The smaller the radius of the pipe, the lower the loads you can trust it. If we are talking about light fences and small garden buildings, then a 76 mm pile will do; about verandas, gazebos and brick fence posts - 89 mm; about small frame or log houses - 108 mm. And finally, if it is planned to build a spacious wooden house or even from a foam block, then for this case, piles with a trunk diameter of at least 133 mm are needed.
Like all building materials, screw piles have negative reviews, but they are no longer dictated by the unsuitability or unreliability of this type of foundation, but by improper use. Any construction requires a professional look and at least a consultation, and as a maximum, an accurate detailed calculation of all structures and loads.
Screw piles: pros and cons
Building a foundation on screw piles has many advantages, such as:
- they are quick and easy to install as they do not require pre-drilling and concreting;
- Pile driving is possible all year round;
- they are absolutely not afraid of difficult terrain, bulk soils;
- they are mass-produced in factories, which means that their cost is much lower than that of traditional types of foundation;
- they can be screwed in and out repeatedly;
- they have good resistance to winterground heaving.
Considering screw piles, the pros and cons of these structures, it is impossible not to mention that from year to year they are becoming more and more popular. And sometimes there are situations that you can’t do without them at all.
Contrary to everything that has been said about screw piles, consider the disadvantages that they have compared to their concrete "brothers": they have a shorter service life due to susceptibility to corrosion in a moist soil environment, especially if their manufacturer uses low-quality materials and processing methods.
In general, the service life of piles depends on many parameters that must be observed: on the thickness and grade of steel, on how professionally the seam connecting the shaft to the blade is made, on the quality of anti-corrosion coatings and on the mineral composition of the soil. If there is a desire to purchase quality products, then it is necessary to require all passports, certificates and documents confirming the conduct and results of all proper tests.
Depending on how to operate the screw piles, the pros and cons may appear to a greater or lesser extent. For example, if a pile is used as a grounding method, then it will most likely collapse and rust, because in the event of a break in the neutral conductor, the current will flow directly through the body of the structure. Screw piles can receive negative reviews if the house is built within a radius of 50 meters from a power plant or cell towers. In such an area, a phenomenon is observed in the soil, calledstray current, which accelerates electrochemical corrosion.
Types of screw piles
Depending on which screw piles are used, the pros and cons, reviews about them may vary. There are 2 varieties of them: with a welded tip and with a cast one (in this case, the pile is a one-piece structure). The second option is more expensive, but more reliable, because the weld is the most vulnerable point of the product.
Almost all negative reviews refer specifically to welded piles, because they are usually made in artisanal conditions with non-compliance with standards and GOSTs.
How to choose the right piles?
You can use welded ones if you need to build minor structures like fences and outbuildings. In other cases, preference should be given to cast, made of galvanized pipe. Anti-corrosion treatment of the blade will not solve the problem, because during screwing in the friction is so high that all coatings are easily rubbed off.
In order not to be disappointed in screw piles, you should purchase them only from trusted suppliers whose quality you are sure of.
