The bearing resistance of friction piles usually increases over time after installation. Recently many studies have been made about time-related increase in bearing resistance of friction piles in several countries. Though, in Finnish soil conditions there are little knowledge of time related increase in bearing resistance. The aim of this master’s thesis was to examine the time dependency of friction pile’s bearing resistance in Finnish soil conditions. The second aim of this thesis was to examine the ability of soil investigation-based pile design methods used in Finland, to predict pile resistance. This study consists of literature and experimental parts. The literature part introduces the pile design methods based on soil investigations and the theories behind the increase of bearing resistance. Also the basic theory behind the dynamic load test and signal matching and some research results of bearing resistance increase of friction piles from abroad are included in the literature part. In the experimental part the test results of two test piling sites are introduced and analyzed. Test pilings were conducted at bridge sites which were located in railway from Liminka to Oulu. Soil conditions at the test sites are challenging as the bedrock surface is located in 60–140 m depth based on investigations by Geological Survey of Finland (Breilin & Putkinen 2012). The test piles were closed end steel pipe piles and driven precast concrete piles. The test piles were investigated by dynamic load testing in four phases: the first phase at the end of driving (EOD), the second phase about 24 hours after the EOD, the third phase about 14 days after the EOD and the last phase about 28 days after the EOD. Signal matching for measured signals was also performed. The study shows that the bearing resistance of friction piles showed significant increase with time. Test results are presented figure 7.13 as well as the results of previous studies about time-related increase in bearing resistance of friction piles. The test results indicate that the major increase happens in two weeks, but also after two weeks the increase is noticeable. According to the literature study the bearing resistance increase will continue over 100 days after EOD. Remarkable costs in piling projects can be saved if the increase in bearing resistance is taken into account. At the test piling sites the design methods based on site investigations gave variable results and clear conclusion about the ability of methods could not be done. There were not enough laboratory tests for soil samples near the test piles and soil parameters such as unit weight and friction angle had not been determined. During the study many further research topics were found. Further research topics are for example the meaning of settlement in dynamic load test to the validity of result and the effect of pile diameter to the increase in bearing resistance.