First, they argue that an alleged wrongdoer must bring
a claim for contribution and indemnity within two years of service
of the underlying statement of claim. They argue that this limitation period is absolute, through the combined operation of ss. 5(2)
and 18 of the Act. Because the claims for contribution were commenced more than two years after service of the claims in the
main action, they were out of time. In the alternative, the Hart
defendants argue that the Murphy defendants and the Amerispec
defendants ought to have discovered their claim more than two
years prior to commencement of the claims for contribution. Thus,
even if the principle of discoverability applies to claims for contribution and indemnity, the claims for contribution in this litigation
should be dismissed on the basis of s. 5(1)(b) of the Act.
 Two issues arise on this motion:
(a) is there an absolute two-year limitation period for claims for
contribution and indemnity under the Act, through the com-
bined operation of ss. 5(2) and 18, with the result that the
claims for contribution ought to be dismissed; and
(b) should the Murphy defendants and the Amerispec defend-
ants have discovered their claims against the Hart defend-
ants more than two years prior to the commencement of the
claims for contribution, with the result that these claims are
barred by s. 5(1)(b) of the Act?
 As is described below, I would answer no to the first question and yes to the second.
 The determination of the issues raised on this motion
turns on the proper interpretation and application of the following provisions of the Act:
Basic limitation period
4. Unless this Act provides otherwise, a proceeding shall not be commenced
in respect of a claim after the second anniversary of the day on which the
claim was discovered.
5(1) A claim is discovered on the earlier of,
(a) the day on which the person with the claim first knew,
( i) that the injury, loss or damage had occurred,