1. Maybe your requirement of ‘No Crack’ scared the hell out of the contractor which they suggest the most expensive foundation method for your extension. Do note most of the extensions would probably crack in time to come due to differential settlement from different foundations at a different timeline.

2. It would be a great laughing stock at the fraternity of the construction industry for a single storey building to have piling foundation for its base. Why ? Cost is expensive and does not justify the return of value.

3. The most economical advice I can give is for you to forgo the piling foundation but to use the raft foundation and connect to your existing structure using post-installed rebar (google HILTI post-installed rebar)for your single storey extension. Surely will not avoid cracks entirely but an economical solution.

4. If you are still paranoid, then you can add bakau pile to your raft foundation (which you can use a backhoe to drive in the bakau pile – cheaper than concrete piling) which most of the 2 storey houses in klang uses (see picture).