Tony
Firstly lets look at it!
You have a customer who has 61M2 Travertine down that they want deep cleaned, filled, repaired and sealed for £700ish!
The simple fact is I can write you step by step instructions on how to do it and "Yes you can do it and it will be brilliant and they will be over the moon".
The bad news is that it will probably take around 3/4 days to do it depending on the amount of holes and cracks that need filling, it will cost you around £200 + VAT in basic materiels to do it properly, so you will end up with about £460 for what is essentially advanced floor restoration! That works out at around £115 a day max!
If we took that job on I would put a team of two guys on it who are highly skilled and it would take them 2-21/2 days and it would be around £1525 + VAT! subject to me seeing it.
You have already said the kitchen is expensive and they would have paid around £1800 for the tiles, £400 for the UFH, adhesive and grout £300 ish then the labour to lay it around £1800 so the floor cost probably about £4300 anyway. The sad fact is that the floor restored properly will make the difference between selling the property and not selling it!
You in my opinion need to explain all that to them and then make the decision of|:
1. Walk away!
2. Do it for peanuts!
3. Do it for half decent money (aound £1200) and take your time and gain the experience for the future!
I am happy for you to come down to us
free of charge (I take it you are still in Sutton Coldfield) and show you the correct way to deep clean and repair travertine!
By the way the cracking is caused by one of two things:
Either they failed to commission the UF Heating system correctly or
The floor was not correctly laid and it has lateral or vertical movement
Kev
