Sharecast - The company said it has a strong balance sheet, with leverage of 1.41x net debt to EBITDA and "a robust pipeline of attractive inorganic investment opportunities".
"However, the board believes that the share buyback programme will provide greater flexibility to achieve an optimal use of cash to deliver value for shareholders, whilst still maintaining a strong balance sheet."
At 0915 BST, the shares were up 5.9% at 733.63p.
Self-storage company Big Yellow on Monday reported a 6.7% rise in first quarter revenue, driven by higher rents.
Sales for the three months to June 30 came in at £48.1m compared with £45.1 million a year earlier. On a like-for-like basis they rose 5.4% to £47m.
The average achieved net rent per square foot rose 9% to £32.74.
FTSE 250 - Risers
W.A.G Payment Solutions (WPS) 94.40p 8.26%
OSB Group (OSB) 360.80p 7.70%
Future (FUTR (LON:FUTR)) 740.50p 6.85%
International Distributions Services (IDS) 230.60p 3.83%
Mobico Group (MCG) 95.75p 2.96%
Paragon Banking Group (PAG) 508.50p 2.60%
PureTech Health (PRTC) 221.00p 2.55%
Hilton Food Group (HFG) 661.00p 2.48%
TUI (LON:TUIT) AG Reg Shs (DI) (TUI) 582.50p 2.46%
IP Group (LON:IPO) 53.20p 2.31%
FTSE 250 - Fallers
Hipgnosis Songs Fund Limited NPV (SONG) 74.00p -3.90%
Coats Group (LON:COA) 65.40p -3.25%
Big Yellow Group (LON:BYG) 987.50p -3.09%
Molten Ventures (GROW) 255.80p -2.89%
Abrdn Private Equity Opportunities Trust (LON:APEO) 442.50p -2.75%
Hammerson (HMSO) 24.00p -2.52%
Shaftesbury Capital (SHC) 109.00p -2.24%
Ferrexpo (LON:FXPO) 86.60p -1.98%
Sirius Real Estate Ltd. (SRE) 83.30p -1.94%
Auction Technology Group (ATG) 707.00p -1.94%