Basements in Ireland

Frank-
This post is about to drop off the front page, and if I don’t respond before it does I’ll forget about it. And it’s an interesting question.

The short answer is I don’t know what planning rules and regs have to say about basements, though they strike me as an eminently sensible idea. I’ve lived in a basement flat of a Georgian on Upper Leeson St and a house with a basement in Ranelagh- the only problems were damp in winter and slightly low ceiling heights, both of which would be easily solvable in a new build. And a friend lived in a basement on Fitzwilliam Square with ceilings higher than most modern houses- over 14 ft at a guess.

I don’t know why they haven’t been a feature of Irish houses in recent times- probably partly a case that development pressure was slight for so much of the latter part of the 20th C., It must cost a bit more to dig a basement that to simply build on the surface and developers aren’t known for wanting to spend money where they’re not obliged to- how else to explain identikit estates?

Apartment developments have belatedly begun to feature basements for storage, not to mention parking, but you seem to be asking about houses exclusively.

I can’t see how it would be out of character with an area, especially if the basement was all but invisible from the front. I’d far prefer see a house being extended down rather than out, subject of course to comfort requirements being satisfied, but that’s not much of an issue. It would preserve open space, and prevent reduction of natural surfaces and thus preserve drainage patterns, not to mention having significant character potential. As a teenager I often wished I lived in an American suburban house as seen in countless sitcoms for precisely this reason- I wanted a basement ‘den’.:)

Much of this is speculation and conjecture- I’d be curious to get an architect’s perspective on the practical realities of such development, either new-build or conversion.

Yes the concept is logical, though not necessarily so if the space is going to be used simply as a dumping ground, a mere replacement for the shed that would stand in a garden that’s going to be there regardless.
But certainly a combination of extra living accommodation, especially bedroom/study space, and storage is most compatible, especially if houses could be developed in a way as to allow the land fall away a little to the rear to permit at least some natural light to come through, if not even revert to an older c1900 model where the house is slightly raised up all the way around by 2/3 steps, like many American homes, to allow small windows front and back, if not even a fully exposed rear wall.

There’s a very interesting case of a basement being put to ‘extreme’ use in Dublin at the minute, though not residential.
Essentially the Royal College of Surgeons want to build a nine storey building on St. Stephen’s Green (York St corner :(), but obviously can’t get away with it. So they’re digging deep – no less than four storeys deep in fact, surely one of the deepest basements to be built in recent times in Dublin.
Were they to build to 4/5 storeys from ground up, they’d consume nearly double the space, so it seems like a great idea.
Saying that, one would wonder about the quantities of energy that’ll be consumed to keep things habitable down there.
Compared with a basic domestic application though, it really puts things in perspective. Basements are more than do-able if the will was there.

Does anyone even know of any recent residential cases in Ireland of basements being used?

I guess it’s a custom. Once asked a local builder about basements. His answer was you’d get twice the floor area above ground for the cost of putting in a basement.

I am aware of one recently built timber-frame house on the road between Tralee and Dingle which has a basement. I only saw it during the construction so not sure how the people living there are using it.

@Frank Taylor wrote:

Thanks for all the replies.

One more question: would a basement make a house more susceptible to radon gas? Someone mentioned this to me and I don’t know if it’s true. I’m going to ring the RPI tomorrow and ask for some advice. I’m thinking of building a house with a basement to be used for utilities and extra living space.

A properly contrusted basement is no more affected my radon gas than a regular house, as long as the workman ship and materials are satisfactory. As long as the right membrane is used it will be fine.

Retrofitting a basement under an existing house can reduce the harmful effect of Radon gas. A properly constructed basement will act as a Radon barrier, whereas many older homes just have raised timer floors over earth that provide no protection.

@mikes wrote:

Retrofitting a basement under an existing house can reduce the harmful effect of Radon gas. A properly constructed basement will act as a Radon barrier, whereas many older homes just have raised timer floors over earth that provide no protection.

Mikes

While I am not doubting the ability of your company, I feel that it should be pointed out that retrofitting a house with a basement as a means of reducing radon is an outragously expensive solution to the problem. Also I feel that you are incorrect when you state that raised timber floors over earth provide no protection againat radon. If the void below the floorboards is ventilated then the radon will escape without collecting in your home. If, in the unlikely event that the space is not ventilated, opes can be made at plinth level very easily and inexpensively without the need for major works.

@paul101 wrote:

Mikes

I feel that it should be pointed out that retrofitting a house with a basement as a means of reducing radon is an outragously expensive solution to the problem.

Agreed! The primary benefit of a basement is gaining additional space in areas where land costs are very high. Alleviating a radon gas problem is a useful side effect.

Useful post, this.
Not only for old city houses/offices, but also for height limited (by council planners) new houses in country on small site.
So many N. American houses have big basements. Many German houses too.
Wonder if Mikes (or interested architects) got a concept basement house for such people.

hmmm I haven’t heard of many rural basements being built because of small sites or planning limitations – yet.

In rural areas typical projects, that I know about, are new builds of large one off family homes, on sizeable sites, where the owner wants big recreation rooms. From what I can see the desire for home cinemas, gyms and pools tend to be drivers for rural basement projects rather than site limitations.

I’m just wondering about the additional costs associated with basements, compared with just building over ordinary foundations. At present my house (end of terrace) has a side extension that’s horrible in just about every conceivable way – appearance, layout, construction quality… I plan to demolish this and replace it with one that’s better designed, and I’m mulling over the possibility of getting extra floor space by including a basement.

From what I’ve read so far, it seems that the cost of retrofitting a basement under the main house would be prohibitive and might also have implications for my neighbours in the terrace. However, if a basement is included in the new extension (just under the new bit) at the time of construction I presume it should be somewhat more cost effective.

Obviously this would have implications for the layout and costs will also vary hugely depending on spec, but could anyone hazard a very, very general guess on how much extra it might cost (either as % or €) to build 2 storeys over basement instead of 2 storeys only? The footprint would basically be a narrow slice between the main house and a tall side wall (I’m guessing about 2.5-3m wide by 9m front to back).

Thanks.

Feature on basements in today’s Financial Times. Haven’t read it yet, but a quick scan showed £500 – 700 per sq foot for retrofit. At the end the article lists websites http://www.bigbasement.co.uk
http://www.cccon.co.uk
http://www.londondigs.net
http://www.ladbrokeassociation.org.
My guess is that you would not add the cost to the value of your home,
Kb2

For once off rural builds it is also worth keeping in mind that a fluctuating watertable quite ofter comes within 2m of the ground surface and putting utilities or toilet facilities in a basement would most probably mean installing a pumping system to evacuate liquids for treatment. The potential lack of natural light would also be a concern.

Thanks for the heads up on the FT article and the links KerryBog2. Thanks also for flagging the water table implications Wild Bill. Food for thought.

I would plan to use the basement space for (a) workshop/hobby space and (b) gym/exercise space, since currently all the gear for these is taking up 2 bedrooms (one each), and when the house only has 3 beds that’s not popular! This would mean the basement area would be used frequently (daily) but not for more than an hour or so by any individual at any given time, so I wouldn’t be as fussed about huge quantities of natural light compared with if it were being used for more intensive living space (living room, bedroom etc.)

I don’t think retrofitting a basement under my existing house would be cost effective. (Certainly not with the retrofit costs quoted by KB2.) However, I’m wondering whether it could be worthwhile to incorporate a basement under a new side extension at the time of building. (Only under the new extension, not also going sideways under the existing house.)

Compared with just having ordinary foundations, a basement would obviously mean:

• digging deeper;
• more intensive waterproofing;
• design implications for the underground space (ventilation, light, emergency access/escape);
• ???possible stability implications for neighbouring (shallower) foundations under existing house;
• fitout costs since used as habitable space not empty shell (although flooring etc. will be fairly basic since just workshop/gym area)..

I guess it’s really an approximation of these extra costs I need to get a handle on, since I would hope including a basement as part of a new build would still come in a lot cheaper than a retrofit under an existing building.

Have you considered building on a larger footprint and building a semi basement with raised patio garden on top?; this is very common in some inner suburbs of London where plots are very tight; it allows the planners in certain boroughs to grant floorspace whilst preserving private open space minimum standards in a manner that doesn’t adversely affect neighbouring plots.

Cobalt,
A big concern should be the possibility of undermining the structure of your existing dwelling with any works for an adjacent basement.
Also – how near are your neighbours away from the site?
Get specific Civil Engineering advice on designing and costing for this aspect of your plan.