Er...isn't it dangerous to drill the wall that is the pillar of your home? I viewed 2 terraces at HH and both have cracks on the walls and they are not fine cracks and spread a big distance across the wall...
Its definitely not recommended especially if its a deep one. You will be surprised though as what constitutes as major cracks or compromises a building.
Have a look at Sengkang, as mentioned below. HDB units should be built to higher standards but defects are prone to occur. Any house/apartment that one buys, remember to go in with your eyes open and a trusted contractor or building expert who can give you some pointers else the worst thing you want is for water to come out from your electrical sockets:
http://forums.fuckwarezone.com.sg/showthread.php?t=511786&page=5
By : Johnson Choo, Channel NewsAsia
SINGAPORE: Sengkang flats have been in the spotlight recently but for all the wrong reasons.
First, construction at several blocks was delayed, then there was an invasion of cockroaches at several other blocks, and now there's water seeping into several flats at a newly completed block at Compassvale.
A 5-room Sengkang flat which is is barely two months old, but its floor has already had to be repaired by HDB contractors twice.
The problem - there's water leaking into the ground floor unit.
The joints, where the walls meet the floor have been re-sealed with water proof material, and the outside walls were hacked open and re-sealed with water-proof material.
Yet less than a week after the latest repairs, water is still slowly seeping through the floor.
Wang Xingwei, affected flat owner said: "Water keeps seeping through the floor in my master-bedroom. My contractor had intended to complete renovation by the end of this month, but now he's having a headache, especially with the parquet floor."
Because of this water seepage, the family has held back delivery of many of the household items they bought earlier.
But this isn't the only unit affected - next door watermarks had appeared on the ceiling, even though the unit above is not occupied.
Another affected flat owner, Weng Zhuping said: "I've complained a couple of times, and the contractor only came to paint over it. Now one week later, the watermark has returned."
And on this 9th floor unit, water is seeping through the wall tiles.
HDB contractors have had to remove them and add more cement to replace the tiles, but they admit it may not solve the problem.
It is believed around 10 units in Block 207C Compassvale are facing similar problems.
HDB has ordered its contractors to fix these leaks, although it won't say if they are the result of shoddy workmanship. - CNA 
