It's a great opportunity to see inside buildings which do not usually welcome visitors, or those which are open on an occasional basis or are used for another function.
Many larger visitor attractions also run exclusive talks, exhibitions, walks and other events to tie in with the month-long festival.
Here are some of the most interesting places to visit in Yorkshire.
Visit www.heritageopendays.org for full local listings.
Calf Cop Friends Meeting House, Low Bentham - open September 14 from 2-4.30pm
This 18th-century Quaker meeting house is Grade II listed and has its own graveyard and allotments. The open day will include an exhibition on the Ford family, who ran a local silk mill and were radical reformers. Frank Ford, the last manager of the mill, will give a talk at 3pm.
Stonefall Cemetery, Harrogate - open September 21 with walks from 11am-12.30pm and 2-3.30pm.
Stonefall Cemetery has over 100 Commonwealth war graves, and is one of the largest military burial sites in the north. Two walks will take place with information on the history of those buried at the site. They include the only pilot from Fiji to serve in the RAF in World War Two and several Soviet servicemen.
Old Magnesia Well Pump Room, Harrogate - open September 14 and 15 from 10am-3.30pm
Located in Valley Gardens, the pump room was built in 1858 to serve magnesia water to Harrogate Spa visitors. When Valley Gardens were opened in 1887, a larger pump room was needed to cope with demand, and the original one was closed and neglected. It was restored by the Friends of Valley Gardens in 2011.
Lock-up and Pinfold, Hunmanby - open September 14 from 10am-1pm
The village still has a Georgian prison cell called a 'lock-up' that was nicknamed the Black Hole by residents. The pinfold was once used to impound stray animals. They are only open once a year.
Scruton Station, Northallerton - open September 15 and 22 from 10am-4pm
Scruton is a restored Victorian railway station that was once on the Wensleydale Line. There will be exhibitions and talks throughout the day about its history.
Aske Hall, Richmond - open September 18 and 19 at 10am, 11am and 12pm - pre-booking essential
The Georgian home of the Marquess of Zetland has been in the Dundas family since the 18th century. It has Capability Brown parkland, a collection of furniture and porcelain, an Italianate chapel, a coach house with carriage, Victorian stable block, walled garden, terraced garden and lake with a Roman-style temple.
The estate is only open to the public for guided tours on a few days of the year.
The Gazebo, Ripon - open September 15 from 2-4pm
Gazebos were built as pavilions in pleasure gardens in the 17th and 18th centuries. Ripon's has survived, as is one of the city's lesser-known treasures which has been restored. Ripon Civic Society open it once a year. It's in the garden of a large house on Park Street, behind the Blossomgate Court sheltered housing complex.
Ayton Castle, Scarborough - open September 14 from 10.30am-4pm
The ruined tower is Grade I listed and is not normally open to the public. An archaeologist will also be giving talks. It was originally a peel tower, built in the 14th century to deter Scottish raiders, and was abandoned in the 17th century.
Central Tramway Company engine room, Scarborough - open September 13, 14, 20 and 21 for pre-booked tours only
The Victorian engine room that powers the clifftop tramway is open for special 45-minute tours. The machinery is not usually visible to the public and still powers the trams today.
The Folly, Settle - open September 14 and 21 at 12pm and 2pm
The Folly is Settle's only Grade I-listed 17th-century building. There are guided tours available at 12pm and 2pm. The restored building is now home to a museum about life in North Craven.
44 Baxtergate, Whitby - open September 14 from 2-5pm
A rare opportunity to see inside a privately-owned Georgian townhouse and talk to its residents. The property was built in 1747 and was refurbished in the 19th century. There are original features including panelling, fire surrounds, fireplaces and roof beams.
Hetty and Betty's Cafe, Whitby - open September 14 and 15 from 10am-4pm
This Grade II-listed building was run as a cafe from 1928, and has a beautiful period ballroom which hosted tea dances. It's recently been restored by new owners. An exhibition will chart the history of the ballroom and the Conservation Area around Baxtergate.
Whitby's historic yards - open September 14 and 15 with walks from 11am-1pm and 2-6pm
The yards are open rows of 17th- and 18th-century cottages with quaint gardens tucked behind the main streets. Residents will be happy to meet visitors. The tours are of Clark's Yard and Borough Place.
Fishergate Postern Tower, York - open September 14 from 10am-4pm
This 500-year-old tower is largely unchanged and has three floors, mullioned windows, a timber roof, battlements, look-out tower and mason's marks. It was built in 1505 where the city walls ended on the banks of the Foss, opposite York Castle.Howsham Mill, York - open September 15 from 10.30am-5pm
Howsham Mill is a restored 18th-century water mill which now generates hydroelectric power for 120 homes. It stands on a small wooded island on the River Derwent.
Th'Owd Towser, Holmfirth - open September 14 and 15 from 10am-4pm
Holmfirth's oldest building dates from 1595 and was built as a prison. It was a later used as a fire station, morgue and ambulance station.
Briarcourt, Lindley, Huddersfield - open September 14 with tours at 10am, 11am, 12pm and 2pm
This Jacobean-style Arts and Crafts house was designed in 1895 as a wedding present for its owner. Most of the original panelling, fitted furniture, plasterwork, stained glass and metalwork survives. A painted frieze by F W Jackson has been conserved and re-instated in the Morning Room.
It was used as council offices for more than 60 years but is now being converted into a private house once again.
Hall of Science, Huddersfield - open September 18 with talk at 7pm
The Hall of Science was built in 1839 for socialist meetings and educational events. The present owners are hosting a talk about its history by local historian of the working class Alan Brooke.
It's thought to be the last Hall of Science still standing - it was sold in the 1840s and became a chapel. It's now home to a painting and decorating firm.
Devonshire Hall, Leeds - open September 13 with tours at 1pm and 2pm
Now a University of Leeds hall of residence for students, the Grade II-listed building was converted from two Victorian villas and retains many original features.
Quebecs Hotel, Leeds - open September 19 with tours as 12pm, 1pm and 2pm
The hotel used to be the Leeds Liberal Club, and boasts a splendid period interior including stained glass window. It appeared in the BBC adaptation of Hercule Poirot mystery The ABC Murders last Christmas.
Georgian Bath House, Wetherby - open September 15 with tour at 2pm
A look around the Bath House and its gardens, as well as the old council offices and chamber with stained glass window and Art Nouveau staircase.
Bishop Burton Walled Garden, Beverley - open September 15 from 10am-5pm
The Bishop Burton estate is now an agricultural college, but the site was once a manor and deer park for the Archbishop of York. It was later acquired by titled families. The Georgian walled garden survives, and was laid out before Bishop Burton Hall was gutted by fire and abandoned. Today the 24 acres of gardens are tended by students.
Butt Farm Anti-Aircraft Battery, Beverley - open September 13, 14 and 15 with tours at 10am and 2pm
This site of a World War Two anti-aircraft battery is rarely open to the public and is on private farmland. Only around 60 of the posts are still left in the country. It was neglected after the war and became overgrown, although the area has been cleared and the four gun emplacements revealed.
Butt Farm is now a caravan and camping site.
Christopher Pickering's House, Hull - open September 16-22, tours at 11am and 11.30am
This early Victorian townhouse at 114 Coltman Street has been saved from decay and is being converted back into a private home by the Kelsey family.
It was once owned by trawler fleet magnate Christopher Pickering, and then his business partner Samuel Haldane. From 1921 until the 1960s, it became a children's clinic and was later turned into flats before falling into disrepair and almost collapsing.
Ivy House, Hedon, Hull - open September 22 from 1-4pm
This Georgian house is open to the public for the first time this autumn. It was home to solicitor James Iveson, who came from a legal family. Several Ivesons were mayors of Hull, and later owners, the Park family, also served the town in mayoral roles. After 1931 it became a private school run by the Fewson sisters for 30 years.
In the 19th century, the follies and features in the gardens were created using relics from old churches, including Hull Minster.
Stepney Station House, Hull - open September 15, 17 and 18 from 2-4pm
This Grade II-listed building dates from the mid-19th century. It was a railway station from 1848 until closure in 1964, and was a private house for the next 40 years. Its condition deteriorated but it has since been restored by an educational charity.
It served the old Victoria Dock branch line which looped around the old part of the city to the seaside resorts of Hornsea and Withernsea.