Extension advice

Barwickpaul

Doible fronted detached house.

House is currently quite wide approx 11m and circa 6m deep as includes a 2 story side extension with a small say 30cm setback. The side extension has a flat roof which im not keen on and also a lower ceiling in the upstairs than rest of the house.

Want to do a full length double story back extension of 4m depth including original house and the side extension. Understand i will def need planning for this due to depth and extending on the back of the extension as well as orig house.

Given im going to need to put a new roof on the extension anyway am considering poss of replacing entire roof of orig house and side extension which would have benefit of giving the house one roof rather than a mismash get rid of nasty flat roof and up ceiling height in current side extension. The current roof is low pitch so would have added benefit of making the roof space high enough to convert.

Questions are:

Any idea of additional cost of putting in new roof for whole house above and beyond just doing the back extension?

How much additional disruption? Whole house needs redecorating anyway.

If i do convert the new roof space at future date would i have permitted development for this?

If i decide to make the roof space a living area as part of main project should I apply for this from start or use the possible permitted development mentioned above?

Cheers

Doozergirl

The requirements for extensions is usually that they have to be subordinate to the main house, which often does mean a drop in the roofline as well.

So you could replace the whole lot, but it would probably still be a mishmash, albeit a neat mishmash of linked roofs.

You need to design the house before anyone can give an idea of costs. Roofs aren't all that easy or predictable to design.

We did have a flat roofed side extension which we turned to a hipped roof. It didn't cost all that much compared to the visual improvement and we left most of the old flat roof in place. Disruption downstairs to us as a result was zero.

Any use of the loft in an area which required planning permission would still require permission and so you should apply all in one go.

Barwickpaul

Thankyou thats useful to know on no permitted development for roof conversion on extended areas.

Hopefully planners dont insist on mishmash of roofs half the point would be to make it look like one house rather than extensions. Its rendered which prob also needs redoing so could easily look like one orig house if planners dont get in the way.

Appreciate it will be guesswork but can anyone give a rough estimate of cost differential between 44m squared of roof on new build extension attaching to existing roof compared with 110 squared roof with 44m being on extension and 66m replacing that on existing house?

Doozergirl

The planners are likely to 'get in the way'.

They like houses to look they have been extended. It adds character to a property and enables the evolving street scene to be read, meaning that similarities between houses can still be seen.

It's a pretty important part of good design and good planning, rather than vast expanses of soulless boxes.

Renovation is not something you can really price on square meterage. All houses are made of different materials, in different configurations, require different types and amounts of work. All of those things cost differing amounts of money.

At the moment you seem to be simplifying the entire design and build process to the lowest common denominator. It doesn't work like that.

Barwickpaul

I think thats a little unwarranted. You and current planning orthodoxy may judge obviously demarcating different stages of a building to be good design. Personally I dislike obvious extensions in different materials tacked on the side and back of buildings and far prefer when they blend as much as possible into the original building.

That doesnt mean I want to make my house a souless box it means I want it to be well designed to my own definition of that phrase.

I would appreciate an idea on price differentials which I do understand can only ever be a guesstimate. If even a guesstimate isnt possible making some broad assumptions then ok.

naf123

It's not easy to estimate how much. It depends on what you want doing and what the specifications are. Insulation , type of tiles , roof windows , etc -

It won't be cheap either way .

Barwickpaul

I realise will be expensive! If both options are just mildly expensive then may as well go for one that makes my house look less like a carbuncle (in my opinion). Now if ones excrutiatingly expensive then oh well.

Does making assumptions help? Just roof extension in concrete tiles no roof windows 1 v shape ridge slight incline no need to access roof so can have struts in roof space.

Roof entire house single v shape concrete tiles reasonable incline needs to be design that retains space inside and joists strong enough to put living space floor on. shouldnt include any costs to convert to living space like stairwell fit out living space insulation roof lights etc etc.

Doozergirl

You need insulation in the loft of your existing house to meet regs. It's part of the job of roofing.

You want a loft that is convertible but not converted, yet much of the costs of a loft conversion is in the roofing work. Not putting a Velux into a new roof if one is intended in future is incredibly poor economy. The cost of scaffolding alone is thousands. Do it all again for a roof light?

No one is going to even give you a ballpark without drawings and plans from someone who knows what they're doing.

I didn't suggest that you wanted to make your house a soul-less box, by the way. I was saying that planning legislation is there with the intention of preventing it.

There are rules and regulations to be complied with. You cannot make any assumptions without some professional guidance and someone at least having seen your house.

Employ a professional.

Barwickpaul

They were assumptions for comparing two options. Cost of actually making the roof area habitable would be considered separately.

Clearly I will engage a professional. I do find rough ballparks useful though 1.5k to 3k per sq m for the extension depending on conditions finish etc as an example.

If you think planning regulation is there with the intention of stopping souless boxes you have a much higher opinion of most new build in the past 20 years than I do.

DavidJonas

Considering that you are planning on adding 65% to your floor space and a new roof over all of it - and since you say the property is detached - have you considered knocking it down and starting over?

That way you could exactly what you want. No VAT on a rebuild.

Not saying it would be cheaper, but there might not be much in it.

edit: I originally wrote adding 40%, but 4m added to 6m is 2/3 extra

Doozergirl

I have a low opinion of developer new builds, which is why I specialise in the renovation, restoration and sympathetic extension of period homes.