Approximately 18 months and at two and a half years old.
The average age would be somewhere around 12 months. But average for babies across the world has nothing to do with it. What matters is what is average for your baby. … You have babies that are pulling up as early as 5 months and walking as early as 7 months, or even earlier. You have babies that began pulling up earlier than you thought he or she would, but refuse to take that first real step until they are 14 months old.  Head control is also delayed, and the majority of children with the condition are unable to hold their heads up independently until after seven months of age. Children with achondroplasia start to walk at approximately 18 months and at two and a half years old around 90 per cent of them can walk. The delay is the result of a combination of muscular weakness in the legs, hypermobility of the knee joints and an unusually large, heavy head, which is difficult to balance. If two people with achondroplasia have a child, there is a 25 per cent risk that the child will receive two copies of the mutated gene (a homozygote for this particular gene) causing significant skeletal abnormalities. Going barefoot helps improve balance and coordination. What to do if your baby doesn’t walk. Don't fret if your child is simply taking her time. But if your child doesn't stand with support at 12 months, can't walk at 18 months, or isn't able to walk steadily at the age of 2 years, bring it up with her doctor. Some perfectly normal children don't walk until they're 16 or 17 months old. During her first year, your baby is busy developing coordination and muscle strength in every part of her body. She'll learn to sit, roll over, and crawl before moving on to pulling up and standing at about 9 months. Confidence votes 19.3K. The average age would be somewhere around 12 months. But average for babies across the world has nothing to do with it. What matters is what is average for your baby. You have babies that are pulling up as early as 5 months and walking as early as 7 months, or even earlier.  The average age to begin walking in a child with down syndrome is 25 months (with a range of 14-42 months), versus a child without down syndrome, where the average age is 13 months with a normal range of 9-17 months.  That's an average age to start walking. Half of all kids are slower than average-that's what average MEANS. My two perfectly normal kids didn't walk until 18 months. It might take your friend's daughter another 6 months yet before she should worry about it.  Best Answer: depends on the child, since all children are different there are no average time frames, some as early as 7-8 months others not until a year or later. If your child is not walking or attempting to walk by a year you may want to talk to your childs doctor. My cousin's child started walking at 9 months, but my son didn't start until he was almost 12 moths. My brother started walking when he was 15 months. They'll do it when they're ready. If you're worried about it, you can ask the pediatrician at the child's next check-up. Red flag: If your child isn't toddling by 14 or 15 months, bring it up with her doctor. This is still within the normal range of development, but now's a good time to check for anything that may be delaying the milestone. 16 to 18 months. With help, your toddler can walk up and down stairs. Here are the steps your child will take on the path to becoming an adept walker. Learning to walk involves much more than footwork! We've also given typical ages, but keep in mind that this is just a rough guideline. Some kids walk as early as 9 months, others as late as 17 months. Most babies take their first steps sometime between 9 and 12 months and are walking well by the time they're 14 or 15 months old. Don't worry if your child takes a little longer, though. Some perfectly normal children don't walk until they're 16 or 17 months old. During her first year, your baby is busy developing coordination and muscle strength in every part of her body. She'll learn to sit, roll over, and crawl before moving on to pulling up and standing at about 9 months. While the average age to start walking is between 12 and 13 months, there is a very broad range of 'normal'. Some babies are up and running at nine months old, while others are still contentedly moving around on all fours or cruising the furniture at 18 months. 
http://www.answers.com/Q/At_what_age_do_babies_walk http://www.socialstyrelsen.se/rarediseases/achondroplasia http://www.babycenter.com/0_baby-milestone-walking_6507.bc http://www.answers.com/Q/What_is_the_average_age_that_a_baby_starts_walking https://www.sharecare.com/health/down-syndrome/when-child-down-syndrome-walk https://answers.yahoo.com/question/index?qid=20090518041622AAQPmUB https://answers.yahoo.com/question/index?qid=20080528102144AAvR0mr http://www.babycenter.com/0_your-childs-walking-timeline_10357004.bc http://www.babycenter.com/0_baby-milestone-walking_6507.bc http://www.kidspot.com.au/Childhood-firsts/Toddler-firsts-First-steps-Is-my-baby-ready-to-walk+6581+736+article.htm
At what age does the average child with achondroplasia start to walk?