# Extension Costs: Single Storey or Two Storey



## Billy

Can anyone please help on the following:


which is cheaper 
- a single story extension that is 10ft by 20ft;
- a two story extension that is 10ft by 10ft

i.e. both have the same area

Also,

does anyone know how is easy or otherwise it is to get planning permission for a two story extension on a terraced house in Dublin?


tks,

Billy.


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## jhegarty

*Re: Extensions*



			
				Billy said:
			
		

> Can anyone please help on the following:
> 
> 
> which is cheaper
> - a single story extension that is 10ft by 20ft;
> - a two story extension that is 10ft by 10ft
> 
> i.e. both have the same area
> 
> Also,
> 
> does anyone know how is easy or otherwise it is to get planning permission for a two story extension on a terraced house in Dublin?
> 
> 
> tks,
> 
> Billy.



Generally, you will _not_ need planning 		  permission for:



Building an extension to the rear of the house which does not increase the original floor area of the house by more than 40 square metres and is not higher than the house. The extension should not reduce the open space at the back of the house to less than 25 square metres which must be reserved exclusively for the use of the occupants of your house. If your house has been extended before, the floor area of the extension you are now proposing and the floor area of any previous extension (including those for which you previously got planning permission) must not exceed 40 square metres. (There are also 			 other height restrictions.)


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## Fly

*Re: Extensions*

I believe it's quite easy as there's been a policy of "upgrading" the housing stock within the city boundaries and from what I hear the authorities are keen to encourage people to improve their houses to accommodate their families rather than move out.
Obviously it depends on it being within keeping with the surrounds etc.  We were asked to change the look of the walls to exactly match the rest of the house (were going to go for a brick rather than plastered finish) but apart from that there were no hitches, and from what I hear, that's typical.


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## B. Bub

*Re: Extensions*

I suspect a 2 storey will be more expensive as it would be more labour intensive as the roof would have to be re-inforced to support the 2nd storey.

I suggest that you run your plans by your neighbours as that would be the main stumbling block to a 2 storey extension.

Also get your architect to run the plans by a planner with the council. The planner will come and take a look at the property and look at your plans and will give you an indication as to whether or not it is worth applying. This of course means nothing and it can still be refused, but at least if the plans are off the wall a planner can tell you straight out whether it's a runner or not.

Bub.


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## Billy

*Re: Extensions*

thanks folks, the replies are much appreciated and very helpful...........


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## GreatDane

Hi

I had head that building an extension in some parts of the Dublin area can run at between €200- €300 psf .. assuming you use a registered builder etc.

However, with a few contacts etc, I gather the figure can be reduced to circa €120 psf

Anyone know how long is planning permission good for, if applied for & obtained, to extend ones family home ?

Cheers

G>


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## OhPinchy

I believe that planning permission is good for 6 months after being granted but after that youd have to apply for an extension (for which the fee is more expensive than the original application fee of €34 I think).

Yes - the 2 storey extension will be significantly more expensive than a single storey even if the square footage is the same. If you are building to the back it will likely be a flat roof that joins the house at the level of the upstairs ceiling. If its at a gable end youve got major extra work as you need an entire new pitched roof for the extension, and assuming you want to capitalise on the much bigger attic space it will give you, you'd need to knock the existing gable wall in the attic, which will require alternative support for the roof.

The flat roof jobs dont look too hot but you probably wont see it from your garden anyway so itll just be an eyesore for your neighbours.

Other factors:
-foundations need to be dug deeper and wider
-you now need joists at first floor level and a flat roof for the extension - more work than just the one roof on a single storey extension, which even though bigger its easier to do one big job than 2 small ones
-scaffolding and the risks associated with 2 storeys make work that bit slower
-a big factor is how will the upper storey tie in with the existing upstairs - you've got to at least knock the back wall which will probably require another RSJ (reinforced steel joist) in addition to the one downstairs, but whats the layout upstairs - do you need to move any other walls. If so are these stud partition or load bearing concrete walls? Moving walls means hassle, which becomes major if theyre load bearing, and think of the associated plastering, skirting, doors etc costs.
-another factor is 2 storey is more hassle for the builder and its regarded as more complex so be sure theyll make you pay for that.

as a ballpark guess for a 200sq ft 2 storey I'd say you'd do well to get it for 70k and the single storey you might get for 50k.

Oh yeh, the post above mentions that you can build an extension to the rear so long as its not bigger than 40 sq metres and not higher than the house. This would imply you can get a 39 sqmetre 2 storey extension without planning permission as long as it is not taller than the house - I would be very very surprised if this is true - I believe any 2 storey extension needs planning permission (give yourself 4 months from date of application to date you're actually allowed build, all going well).


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## jhegarty

OhPinchy said:
			
		

> Oh yeh, the post above mentions that you can build an extension to the rear so long as its not bigger than 40 sq metres and not higher than the house. This would imply you can get a 39 sqmetre 2 storey extension without planning permission as long as it is not taller than the house - I would be very very surprised if this is true - I believe any 2 storey extension needs planning permission (give yourself 4 months from date of application to date you're actually allowed build, all going well).



source of info :


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## Billy

thanks a mill to everyone who replied,  I'm a bit blown away by the quality of the responses......Billy.


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## 1150RT

Planning permission will last for 5 years. If in doubt phone your local Authority Planning Department. By then you must be substantially built. 2 storey is more expensive and difficult than single storey - both to design and to build. Foundations and outside walls would be the same size anyway (unless uour house in on a marsh). If going for a single storey option, think about building in a "future proof" design such as a couple of steel beams in the flat roof to take a future first floor extension or a soil pipe & drainage from a upstairs bathroom.


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