RatFloofing

Thanks all for input - have given me some things to think about. In terms of what we want to use it for, currently there's an empty hot tub sunk into the floor but being realistic I doubt we'll ever actually use it (might even be worth getting it taken out). Probably just a 'nice place to be' during the warmer months (& my partner likes it as an art studio!) - we visited in May, July and September before buying and the temperature seemed ok all those times - even though it's south facing it does have shade from the trees. When I think about it, in a few years time I'm probably more likely to regret making lots of tradeoffs just in the interest of saving money at the time, but it doesn't make it easier. Surrey - so not far off central London for value It has electric UFH right now. The rest of the house has wet UFH (which also has some really weird issues / mistakes with the installation) but I'm not sure it would be very easy to get it extended out to here as well

Hi - We recently moved into a house with a large extension (about 6.5x5.5m in the main area) that has a flat roof and a frankly enormous 'rooflight' (about 4.5x3m) As we've now discovered the whole roof and rooflight needs replacing because the structure is totally insufficient for the rooflight, as well as a bunch of other problems like no ventilation at-all for the cold deck roof and no vapour barrier the 'rooflight' is actually just a lean-to roof panel that's been plonked on top and isn't really suitable for how it's been used So, we've basically got free reign to replace it with something sensible, which includes Rebuilding the whole roof structure and probably making it warm deck Choosing how big / how many rooflights to put in (and associated steel work) Re-covering roof and finishing interior (e.g. board and skim, re-wire lighting) (Tbh, we don't really need this room so it's become a bit of a burden. It's more like a conservatory in that it has electric heating and we've got it closed off from the rest of the house at the minute to avoid wasting money heating it. But we still want it to have a decent amount of roof opening to avoid having a dark corner of the house) I have an architect / structural engineer who is coming soon to measure up for drawings. The problem is I'm struggling with all the different options for the roof and how much they might cost. Firstly, I have no idea even a ballpark figure what the absolute cost is going to be, whether it might be £15k or £50k, so I don't know whether I need to try and economise or not. It's a bit of a chicken and egg situation - I've talked to a couple of builders, but they won't give me a quote without a spec / drawing, and I don't know what to tell the SE to draw without some idea of whether / where to save costs. For example, I could: Try and recreate the size they've made but do it properly (We don't really need it to be this big and it's probably not a great idea - might be a challenge with U-values and the like?) Go for 1 big roof lantern that's not as big as this (e.g. 4m x 2m - would still need steel) Go for a couple of rooflights / lanterns (e.g. 3m x 1.5m - is that excessive? would still need steel) Go for more small rooflights (e.g. 1.5m x 1m - probably wouldn't need steel) Countless other options But - is increasing the number of rooflights to save on the cost of support a false economy? Would it make any meaningful savings (or savings at-all) since I assume there's an overhead in cost for each rooflight that's put in. Is there any kind of rule of thumb for the rooflight / steel size trade off? Or am I wasting my time thinking about it and I should just go for what I think looks best while meeting regs? Any help with understanding this appreciated. Thanks! (edit: located in Surrey if it's relevant)