Arsonists are suspected to have torched a new home in Hayle causing hundreds of thousands of pounds damage.
Police have launched an investigation into the alleged attack, which saw more than 40 firefighters called to tackle the blaze on Trelissick Road last night.
The porch was destroyed by the fire and the inside of the property was also damaged.
The three bedroom, two bathroom house, which was being built by St Ives developer Porthia Homes, is on the market for £345,000.
This morning director of the company, Bill Baitup was on the scene counting the cost of the damage, which he estimated to be at around £200,000.
He said work on the property had just been finished and it was about to be sold.
He said: "It was looking absolutely perfect. We had an offer that was proceeding so we nearly got it sold.
"It is still going to be sold because we will have to get it sorted out. It is going to be worse than a rebuild."
Mr Baitup said the fire service had told him the blaze had been deliberate.
He said: "The fire brigade have confirmed that it was arson because pallets were dragged round to the front."
Mr Baitup added: "We have been building it for the last six months and it is going to be almost a total rebuild ... It is totally gutted inside."
The new home, which is currently being advertised for sale on This is Cornwall's sister site This is Property, is described as being a "contemporary home situated in a highly regarded residential area on the outskirts of Hayle offering spacious and well proportioned accommodation".
The internal fittings including carpet and appliances had already been installed.
Emergency services were called to the scene just before 12.30am.
Firefighters from Camborne and St Ives found the porch had been completely destroyed and the fire had spread to the roof.
As the fire spread more crews were called out until there were a total of 42 firefighters on the scene.
A spokesman for the fire service said firefighters from Penzance were called out to the fire as well as units from St Just and Falmouth.
By 3.30am the fire was out and the crews were "damping down" the site.
Penzance Inspector Jean Phillips said police would now carryout door-to-door enquiries in the area and investigate what motive there might have been for setting the fire.
She said: "The fire brigade are satisfied that it is arson and we have tasked the criminal investigation department (CID) to take on the enquiry.
"We are looking for anybody who saw any suspicious activity any time after 11pm."
Anyone with information can contact police by dialling 101 and quoting crime reference number AY-13-376.
