# Building house on top of bungalow.



## MRTULES (27 Nov 2009)

Hi everyone,

First time poster long time reader.

I am looking to build a “house” on top of an existing flat roof bungalow. I have met with architect, had pre-plans checked and approved in principle. Did a bit more fine details and sent it off to quantity surveyor for costing. It came back the other day at €280k. That is not what I was expecting at all (hoping for less). It is rectangle in shape, 120 square meters and flat roof. The house below it has been passed as safe to build on. The fact that foundations were not required, was leading me to believe this would save costs. I saw the figures on the SCS website for Re-build costs. Could they have come down since March? I am looking for anyone’s opinion on what is the cheapest price this could be built for. I would prefer to start there and add on things that I deem to be worth the money as apposed to what I have to do at the moment which is start cutting things back from 280k. 

Also now that I am unemployed I am considering devoting all my time to the build. The chances of me picking up work at the moment are slim and anything I do get will more than lightly be paying less than 25k per annum. I feel I could save more than this on the build by doing as much as possible myself. I have no trade or experience and as such my ability to help might be limited to labouring and basic DIY. Are there any courses I could do? Block laying? Plastering? It is going to be a timber frame build and we were talking about trying to get close to passive housing standards.

Even though I have read and reread this before posting, I am sure I have left out a lot of basic points. Also, apologies for such a long winded post as a virgin poster I hope to improve.

Thanks in advance.


----------



## onq (27 Nov 2009)

MRTULES,

120 sqm is the size of a house and I understand that this is the new work, not the total.

Its going to cost a lot to build and €280 may be about right, given there will be some demolition
Its not very logical to suggest your costs will arise totally from the new build, i.e. first floor level up.
Probably all you'll retain of the existing house will be the bare outer walls which you say are declared sound.
[Who has passed these, BTW - a competent engineer, and did they open up the foundation at two corners and inspect or just guess?]

There will be a lot of new work even at the lower level:


 the existing ceiling will be removed to allow new structures to be built up to support the roof.
 I'd suggest you do not use the existing ceiling/roof joists as these are more than likely designed for roof loads including snow load, not live and dead floor loads.
 new loadbearing walls and piers will probably be needed to support the new floor timbers - this just a fact of life. If you're now living on two levels and unless this is intended as a Duplex flat for profit, the old space divisions on ground floor are likely to be redundant and the spans suggested by the area are significant enough 10x12M for a "square" plan, with 4.4-5.0M or so being the largest economical span in timber.
 each new wall will need foundations to be installed for it - although there are a few workaounds. This is simply good practice and once you start piercing the floor your costs will rocket - concrete is a lot harder to dig out than bare earth, and it leaves your existing DPM in a mess - plus you should consider your Radon Gas options at this time.
All this is before you get seriously into the superstructure and with a flat roof of 120sqm plus [a 200mm eaves overhang will add to this at a rate of 1 sq.m. per 5M of eaves length] you're want to invest in properly tying it down with the high winds we're getting these days.

Given the floor area and the fact that some self builders here are suggesting €100/sqft is attainable, you might be better off knocking the lot and starting again [€240K instead of €280K], but you have to factor in demolition and carting away [an extra €20K or more]. But I expect your architect has aready told you this and the likely high cost of the build - you didn't believe him and your chickens have come home to roost.

I have to say fair dues to you for attempting such a project facing into unemployment, but I'll urge caution as well. Take a look at the self build FAQ Key Post [still a work in progress by yours truly] and make sure you;ve done all the checks required. Then do some costings and find out how you're going to fund the build and paying back the loan. Also price a similarly sized house [240sqm] in your location and see what it might fetch in the current market. Don't get burnt.

ONQ.


----------



## MRTULES (27 Nov 2009)

Thanks ONQ,

I have read a lot of your advice on different threads and the key posts. Most informative I must say.
Firstly I should say that the current bungalow is inhabited and will continue to be for along time. The only structural change to this house will be the removal of the roof not the existing ceiling. Just to reiterate, the current bungalow will not be touched (except the roof) and a new 120sqm house will be built on top. The roof of the new house will be the same as the old one, a parapet roof, not totally flat. So no eaves either. The fact that some people were suggesting that €100/sqft was attainable had lead me to hope that 130k was potentially possible. I have priced semi D’s in the area and a friend of mine recently bought one for 300k. The whole point of building on top of this house in the first place is that we could not afford a house in this area, an area where we have both lived all of our lives and would like to continue to live here for the foreseeable future.


----------



## Sconhome (27 Nov 2009)

MRTULES,

This as a project is not as straight forward as it may initially seem. Not to put you off or to hike costs but there are many issues which need to be considered.

Primarily a QS is not a builder and as such you should use their costings as a budget guide for tendering ie quotes within 15 -20 % positive or negative to the budget are feasible, any tenders outside of this budget are ones to be wary of.

I would encourage you to put your job to tender. Pick 3-5 contractors and ask for a competitive tender in order to consider the real cost of doing the work. I agree, the rates seem on the outside of reasonable, but the QS is doing their job giving the outside rates so there are no major shocks.

You may find that you can save more in the longer run by employing a main contractor and working as a site assistant. Being available for key decisions can save a lot of time and money, once they are not variation works.

In removing the roof and building up you need to think about increased loading on the bearing walls and foundations. Not only is it the weight of the structure, including timber frame you need to consider, it is also the increased loading caused by the more exposed roof level.

I would expect a good engineer is going to suggest a steel frame wrapping the existing house (less roof) and building the second storey suspended off the frame rather than resting on the walls of the ground floor. This will stiffen the timber frame element and eliminate the torsion on the lower walls.

You will be well able to achieve a lower build cost than what you have been guided, clever planning and project management will save a small fortune for you.

As to courses, if you are any way handy, you will learn a lot more from simple mistakes than anything you will learn in a basic course. If you have no skill in your hands, dont bother embarking on a steep learning curve, get that done by someone else who knows, it will save you time, money and skint knuckles.

Sean


----------



## onq (27 Nov 2009)

MRTULES said:


> Thanks ONQ,
> 
> I have read a lot of your advice on different threads and the key posts. Most informative I must say.



You're very welcome, as are all who find my comments useful or informative - that's what this forum is all about.
Sometimes I post too much, but I prefer to qualify my advice where I can. This thread of yours is exercising me greatly.



> Firstly I should say that the current bungalow is inhabited and will continue to be for along time.



This may hugely complicate your health and safety file. Normally when people continue to occupy part of a premises which is being extended, it is possible to facilitate this by a vertical separation of the works from the accommodation.

Usually this can occur when the house is being extended to the side or the rear, and it is possible to use separate entrances for house and works, even if this may require temporary kitchen and toilet accommodation.

You OTOH appear to be proposing a horizontal segregation of house and works, but in reality this is not what's gong to happen. The works will be carried out at high level over the living accommodation and this carries significant risk to all concerned. Full perimeter access will be required if you intend to build off the existing walls and that implies full scaffolding too.



> The only structural change to this house will be the removal of the roof not the existing ceiling. Just to reiterate, the current bungalow will not be touched (except the roof) and a new 120sqm house will be built on top. The roof of the new house will be the same as the old one, a parapet roof, not totally flat. So no eaves either.



I'm not sure I see the difference where a flat roof in concerned since the ceiling attaches to the roof in an intrinsic manner. I mean, what holds up the ceiling? Or is there a crawl space overhead and a roof above that again? Remember teh stub walls for the parapet may not be the same thickness as the walls lower down, and you may need to take these down to the "thicker" level and build up again. This may in turn require you to very the roof support detail.

I'm also unclear about the structural or services method here. You appear to be suggesting a clear span of up to 10M [recall the "square" plan of 10Mx12M to give 120sqm area]. Even is this is more stretched out, to say 8Mx15M, this is still a massive clear span and  in normal domestic construction it would require a cross wall or line of intermediate supports coming up at intervals through the existing house to break the span into 2No. circa 4M lengths.

If you are going to span this in one go, you need to check your structural assumptions and calculations again. A steel frame is lighter to begin with but will generate point loadings and requires to be fire-proofed. This suggests a cradle or cage outside the existing house per Sconhome's suggestion. 

A concrete wide plank system will need perimeter support and careful positioning of services cores for pipework, etc., in fact all the services need careful consideration and may need fireproofing including the waste outlets.. The plank system may be happy with a simple linear continuous wall or ring beam for support, but it seems that the overall weight on the existing walls will be significant without an intermediate spine wall to take half the floor and roof load.

It seems that you are proposing two separate residential units separated by what effectively seems to be a compartment floor. Whether this is directly above the existing ceiling or not I think it will act as a compartment floor, and even if you're proposing this as a granny flat to be used as family accommodation I'm not sure any lesser standard will apply. This may need FR 60 construction.

If this isn't a granny flat, then the proposed development seems to be effectively two separate houses - as in apartments - one atop the other.  Although the units may have separate accesses and means of escape they are separated by a compartment floor, not a Separating Wall. This suggests that a Fire Safety Certificate may be required.

I have little direct experience of Duplexes and any granny flat I have provided has had interconnected fire Detection and Alarms Systems and minimum FR60 structural complementation and multiple alternate exits from upper levels. When in doubt ask the Building Control Officer or the DOE for a definitive comment. It all adds to the complexity and expense of what you are doing.



> The fact that some people were suggesting that €100/sqft was attainable had lead me to hope that 130k was potentially possible. I have priced semi D’s in the area and a friend of mine recently bought one for 300k. The whole point of building on top of this house in the first place is that we could not afford a house in this area, an area where we have both lived all of our lives and would like to continue to live here for the foreseeable future.



Well I see where you are coming from MRTULES, but in terms of economical building practices, I'm sorry to say your proposal isn't a semi-D.

Semi-D's save in every way your development doesn't, including needing only three out of four walls to be external, and having a very good almost cube-like shape to minimise heat loss - the closer to a globe the better, whereas your proposed development seems strung out and flat, more like a cigar.

Standard Semi-D's benefit over bungalows in that they make more efficient use of their foundations, and they employ a cross wall to halve their major spans to allow them use lower stressed, low-embodied energy [and therefore cheaper] timber construction.

They also have no need for fire sealing apart from the party wall, which can be achieved by cavity barriers at the eaves and resilient Rockwool under the roof covering.

When you look back at all the issues raised above, you can see where the costs might arise in your build, which is why I took you along this little voyage of discovery.



Having said that, your proposal, Fire Cert and Fire Proofing notwithstanding, may lend itself to off site pre-fabrication in a big way, and once you decide to plump for the erection of a crane on site to assist with the build economies of scale in production and time on site may allow you to bring costs down again.

I think you'll need someone who knows how to design for off-site prefabrication and on-site dry trades assembly and this may in turn suggest one of the several system builders as opposed to a more traditional build route. Using the frame method suggested by Sconhome, you could end up with a very quick time to erection on site and minimal intrusion into the land with little or no effect on the existing house except perhaps for lateral support.

Be careful with wind bracing, the suction effect on large flat roofs and the wind loading on lightweight structures with large side areas.

Finally I'd just like to draw what I see as a clear distinction between "doing a course" and "Learning a trade".
People in offices, in marketing, public relations office management and the professions go on courses.
People who work their wonders with their hands and materials in the real world learn a trade.

Courses last for 6 months or a year at the end of which you get a cert.
Apprenticeships last for 4 years at the end of which you have a skill.

If you learn nothing else here "stick to what you're good at".
Work as a tradesman's mate if you like, you'll learn a lot.
Just don't think you can do what they do.
They make it all look so easy...

There's no doubt what you're doing is doable and to some the level of the detail above is just so much "stuff" [although you cannot build without it].
What I'd really be interested to see is how your architect dealt with the design of the new extension and how he expressed it.
Links to photos/.jpegs or pdf files of  elevations. sections or plans would be appreciated.

HTH

ONQ.


----------



## Bronte (30 Nov 2009)

Would it be cheaper to knock the existing house and start from scratch?


----------



## onq (30 Nov 2009)

Bronte said:


> Would it be cheaper to knock the existing house and start from scratch?



Hard to say, but you could hazard a guess.

To knock one and build two houses of 1300 sqft even at €100/sqft would be €260K plus site clearance costs and alternative accommodation for the people living in the existing house.

There might not be much in it, but with your suggestion you've have two traditional houses without the large spans of the second "upper" house.

The spread of tenders might indeed save some money on the existing quotation.

Still I get the feeling from the OP's posts that the existing house has sentimental value for him - that's unquantifiable. 

ONQ.


----------

