Financing a house extension

[Mybabystolemysanity]

Can anyone shed any light for me on how a lender would value our property with a view to releasing about £30k for an extension?

Bought in 2014 for £145k, £110ish outstanding on the mortgage and valued by surveyor for Scottish home report at £180k in January.

We want to do an extension to the side to add a master bedroom, ensuite and walk in wardrobe and think the house might be worth about £200-215 when finished, although we wouldn't be selling it.

What valuation would a lender use to calculate a new mortgage? Current mortgage, loan outstanding to non extended valuation, new loan to new valuation or something totally different?

Thanks in advance for any insight!

Mortg valuations are based on the value of the property when you take the mortgage out. So if valued at 180k with a mortgage of 140k, your ltv would be 78%.

If you want a better interest rate based on a better ltv, you'd need to remortgage again when the work is done. 140k on a house worth 210k would change ltv to 67%.