in terms of providing a solution to your problem, as ian roch... pointed out...whether its you or somebody working on your behalf doin the job, as part of the site survey always check the existing carpet, and cover yourself first and foremost.
you see the carpet may have been fairly short to begin with...?
anyway, if its a very cheap rubber backed carpet, you wont get much stretch out of it.is the floor concrete? or wood? if wood, you can buy some gimp pins and stretch and pin, the pins r so small they will be invisible to the eye...DIY shops stock em..concrete will be sprayed.
unless its a cord on underlay, which i very much doubt.although not uncommon. it may stretch sufficiently...cheap thin cords can only take a small degree of stretching before they rip though
if its a more heavy duty cord, with a thicker rubber backing, feels quite substantial to the touch.usually, across the board of manufacturers, you can get a very gd stretch, 2 cm shouldnt be a problem, on the length and always less on the width... - however, if its stick down and not on grips/underlay fold the carpet back to the centre/middle and spray it with spray adhesive then stretch towards each end of the room, whilst spray too...either carpet type will be a problem to anyone inexperienced...
and to the experienced... a bit of a ball-ache..
problem will be exacerabated if theres no underlay and its a cheapo thin cord thats been heavily stuck to the floor, as the backing will separate from the carpet if the carpet is lifted up.
in summary - thin cord stuck to floor - problemo, approach with caution, if heavilty stuck ur f*kd!
thin cord on grip/underlay - more chance of a stretch, press one end onto grips, and work in opposite direction stretching to the other end until on grips
thicker cord stuck to floor - more solid rubber backing, more chance of stretching spraying and stretch
thicker cord on grip/underlay - happys days - easy stretch.
hope this has helped...and ive covered everything...if not jus ask..baz x
i could go on all day...i hope im been of some help...all qs us ask...