The value of semis rose by 5.6% over the year, the Land Registry figures show, ahead of flats (up 5.4%) and detached homes (up 5.1%).
Overall, property prices increased by 5.1% over the year and by 0.9% from March to April.
The average home was valued at Â£179,817, the Land Registry said.
Prices rose the fastest in London over the year, up 10.9%, and in the South East of England, up 8.8%.
The slowest annual property price growth was in Wales, up 0.3%. Prices in Wales fell by 1.1% in April compared with March.
The pace of property price rises generally has slowed, although the picture features significant regional differences.
"The property market in Wales and the North East [of England] is a million miles away from the south-east corner of England," said Jonathan Samuels, chief executive of Dragonfly Property Finance.
"The broader fall in the number of property transactions over the last year suggests a natural slowdown in the property market after a period of exuberance."
The figures come as insurer Legal and General said there was a need for purpose-built homes for the older generation.
Nigel Wilson, chief executive of L&G, said that there were more than five million under-occupied homes owned by the over 55s.
Two-thirds of them were looking to downsize but there were no appropriate homes for them, he said.

The Virginia-based court said the president's broad immigration power was "not absolute" and the ban "intended to bar Muslims from this country".
The decision upheld a lower Maryland court ruling that found the ban violated constitutional rights.
The justice department said it would now seek a Supreme Court review of the appeals verdict.
Attorney General Jeff Sessions said the verdict thwarted Mr Trump's effort to protect US national security.
Mr Trump's revised executive order would have placed a temporary ban on people from six mainly Muslim countries and the refugee programme.
The US government argues federal immigration laws grant the president broad powers to stop foreigners from entering the country.
But Chief Judge Roger L Gregory, who wrote the majority opinion for the Fourth Circuit Court of Appeals, said on Thursday that Mr Trump's powers had limits.
"It cannot go unchecked when, as here, the president wields it through an executive edict that stands to cause irreparable harm to individuals across this nation," said Judge Gregory.
The court added that the government's national security argument was a "secondary justification for an executive order rooted in religious animus and intended to bar Muslims from this country".
The decision means citizens from Iran, Sudan, Somalia, Yemen, Syria and Libya can continue travelling to the US.
The 10-3 ruling is the latest in a series of legal setbacks for an order the president insists is needed to stop terrorists from entering the country.
Two lower court rulings blocked the ban just hours before it was due to begin in March.
A Maryland judge ruled that the order was meant to be a ban on Muslims and violated the first amendment of the US constitution.
A federal judge in Hawaii also sided with opponents that the ban was discriminatory and cited "questionable evidence" in the government's argument that the ban was a matter of national security.
The justice department has appealed against the Hawaii decision to the Ninth Circuit Court of Appeals, which heard oral arguments for the case on 15 May.
The Ninth Circuit is the same court that refused to lift a block on Mr Trump's initial travel ban signed on 27 January.
That order took effect for seven days before a federal judge in Seattle halted it.
Instead of appealing against the decision to the Supreme Court, Mr Trump issued a revised version on 6 March.
Washington Attorney General Bob Ferguson issued a statement after Thursday's ruling calling it an "important victory for the rule of law".
"I will support challenges to this illegal and unconstitutional executive order as our own case against the travel ban continues in federal court here in Washington."
Mr Sessions said in a statement that Mr Trump was abiding by the US constitution and was doing his "duty to protect our communities from terrorism".
"This Department of Justice will continue to vigorously defend the power and duty of the Executive Branch to protect the people of this country from danger", he added.
The controversial ban has prompted protests and debate across the US.
More recently, a North Carolina group of pastors highlighted the issue on a billboard citing the 9/11 attacks in Catawba County.
The sign, paid for by the North Carolina Pastors Network, reads: "19 Muslim immigrants killed 2977 Americans", referring to the 9/11 attacks.
The price of semi-detached homes rose at the fastest rate of any property type in England and Wales in the year to the end of April, data shows.
[NEXT_CONCEPT]
A US federal appeals court has refused to lift a temporary block on President Donald Trump's revised travel ban.