Property valuation

I was planning on buying my ex share of the family home. We have had the property valued by a RICS valuer. They have provided two values, first as it is currently 530k (3 bed house) and second if building regulations are sought for the loft room (4 bed house) 590k. The ex's solicitor believes gaining building regulations is just a matter of applying to the council for a certificate and paying a fee and therefore the value of 590k is appropriate. But building regs were not granted because there are changes needed to the property to comply. I am willing to stretch to 530k but couldnt get a mortgage to cover 590k, so the house would need to be sold. I live in the house with my two children (17&19) both in full time education. It strikes me that suggesting a higher value if work is undertaken at my cost is unrealistic and the value of the property is as it is now, not what it would be worth after modification. Is this reasonable?

Take the middle ground in the valuation as compromise?

It wouldn't be a compromise it would be disadvantageous to me. I spoke with my solicitor who suggested the following. Take the valuation at 590k, assume the actual sale price would be 95% of the asking price (while an independent valuation, only one of 5 estate agents said it should be marketed at 590k as a 4-bed with building regulation in place, and the rest less), take of 3% as the cost of sale, take off the costs of repairs necessary for building regulations and the cost of retrospective permission. This left about 537k, take 50% of the difference 3.5k, add it to the offer to buy their share, making 535.5k. A lot less than splitting the difference between 590k and 530k (560k).

Why would you take off 3% for the cost of sale if you’re not selling?

When you get to final bit why are you halving the £7k difference?

3% is standard practice, it is a cost avoided by not selling, so is factored in. Halving the 7k is because the equity is being split 50/50, so half of the additional 7k would be mine and half for the ex.

But by taking 50% of the £7k off the equity and then halving the equity you are effectively halving it twice,

As for the sales costs why would your ex be willing to pay half of a cost that hasn’t been incurred? As you have pointed out there are no sales costs.

If it’s valued at £530k then I’d argue that that is its value.

Yes, I see your point about halving the 7k as equity twice, thank you, saved the ex £350 having her solicitor write and point it out to me. In terms of costs of sale the solicitor view was that a court would insist these are included whether the house is sold or not. It is a deferred liability, the house will be sold at some time and they will be incurred (probably at a higher figure if the house increases in value).