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[F1 9LFG]

Hi all

So I've got PP for a 6m x 6m 2 storey side extension, While I'm at it I've been looking at building a basement into the extension.

This is what I have planning Permission for:



Basement here??:



The basement would be 6m x 6m - a massive space to gain, with a verity of potential uses.

I've read on quite a few websites that by building a basement as part of a new extension isn't anywhere near the cost of building a stand-alone basement as the basement walls are engineered to form the foundation of the extension above - this sounds about right.

No idea of costs as yet but thoughts would be good. It seems too much space to 'not have' but thats obviously dependant on cost!   

Rob 

[05omegav6]

If your house faces downhill, ideal opportunity for a double garage

[Andy H]

If you are equipped to dig your own hole and pour your own concrete then why not?

Regular house builders will run a mile because it is outside the norm (in this country) unfortunately.

[F1 9LFG]

If your house faces downhill, ideal opportunity for a double garage

Sadly not - great idea though!!

Only 4m to the road too so it would be a bit of a ramp!

[F1 9LFG]

If you are equipped to dig your own hole and pour your own concrete then why not?

Regular house builders will run a mile because it is outside the norm (in this country) unfortunately.

TBH it's beyond my abilities, I'm planning to dig footings if I don't have the basement but otherwise it'd be a contractor.

Basements are a specialist area, wouldn't want an underground pond!

As you say, yet to see anyone that'll consider it but still got many companies to try.

[chrisgixer]

There a solutions for water gathering, such as tanking and bilge pumps. All very doable.

[Marks DTM Calib]

That's one hell of a lot of spoil to remove (72+ m2²) and remember your footings have to go beyond the floor of the basement. It then needs tanking and a pump or other water removal method adding.

[F1 9LFG]

There a solutions for water gathering, such as tanking and bilge pumps. All very doable.

Indeed, Ive seen a few companies online (USA) who do these builds all the time, they all state that if it's built correctly in the first place it'll be water-tight and remain so, but it's so unusual over here there doesn't seem to be many companies with the ability, seen some that carry out major builds but they wouldn't look at domestic 'smaller' jobs

[F1 9LFG]

That's one hell of a lot of spoil to remove (72+ m2²) and remember your footings have to go beyond the floor of the basement. It then needs tanking and a pump or other water removal method adding.

yes it is a lot, I can utilise 35-40m2 on site as the rear of the garden slopes a fair bit, still need a 'few' skips/grab lorries though!

It's one of those things 'while I'm at it, could I do this too.......' 

[05omegav6]

This episode of Grand Designs will be of interest

http://www.visitcumbria.com/evnp/underground-house/

[F1 9LFG]

This episode of Grand Designs will be of interest

http://www.visitcumbria.com/evnp/underground-house/

  thats a tad more than I was looking at!! impressive though. Remember seeing that one a while ago

[chrisgixer]

I'd imagine the depth of the floor strengthening, the thickness of the wall/existing foundations, and as said floor and pump need to be factored in to those drawings.


Ime you need to be EXCEPTIONALLY careful in choosing a contractor. As you suggest, conversely, this has serious repercussions if the cowboys get the job. You need someone who knows what they are doing.

My Mum had a listed building with a natural spring running thought the sellar, which was water logged up to a meter permanently for years prior to her ownership. The guy they took advice from for tanking the sellar had done numerous jobs prior to, but utterly failed on this one.

The following case went to the courts and bankrupted his company, allegedly, and took 5 years  total to complete the job with a new contractor.

Yours probably won't have a spring, but shows what can go wrong, potentially. Not to mention possible subsidence.

Shame the roof is so shallow, a nice loft extension would be safer.

[05omegav6]

Pay attention it was on telly again recently...

Alot of detail about waterproofing and insulation the underground floor and walls

[F1 9LFG]

I'd imagine the depth of the floor strengthening, the thickness of the wall/existing foundations, and as said floor and pump need to be factored in to those drawings.


Ime you need to be EXCEPTIONALLY careful in choosing a contractor. As you suggest, conversely, this has serious repercussions if the cowboys get the job. You need someone who knows what they are doing.

My Mum had a listed building with a natural spring running thought the sellar, which was water logged up to a meter permanently for years prior to her ownership. The guy they took advice from for tanking the sellar had done numerous jobs prior to, but utterly failed on this one.

The following case went to the courts and bankrupted his company, allegedly, and took 5 years  total to complete the job with a new contractor.

Yours probably won't have a spring, but shows what can go wrong, potentially. Not to mention possible subsidence.

Shame the roof is so shallow, a nice loft extension would be safer.

That sounds awful, That is my main concern, getting the right builder but not end up spending more than the house is worth! The loft would have been great but as you say, too shallow to make good use of it

[F1 9LFG]

Pay attention it was on telly again recently...

Alot of detail about waterproofing and insulation the underground floor and walls

A re-run of grand designs, surely not...! 

But yes, right you are - some good educational content in that one regarding waterproofing etc.