Developers who have signed the pact are Persimmon, Taylor Wimpey, Lovell, McCarthy and Stone, Countryside, Vistry, Redrow, Crest Nicholson and Barratt.
Y datblygwyr sydd wedi arwyddo'r cytundeb yw Persimmon, Taylor Wimpey, Lovell, McCarthy a Stone, Countryside, Vistry, Redrow, Crest Nicholson a Barratt.