`Basements, and the change to B.S.8102

[Big Jimbo]

Has anybody else seen that the old BS from 2009 relating to Basement building has changed to BS8102 in 2022 ?

It makes interesting reading and would appear to be quite a change. The onus now appears to be that the ingress of water should be stopped from the outside, and that the fill of any excavation should be left open untill any remedial work to prevent ingress is carried out from the outside.

I would appear that the days of letting the water in, and then dealing with it once inside might be over.

My own thoughts are that it might now make it more difficult to build basements from materials such as ICF, Blockwork etc.

The suggestion seems to be that the trademanship of building basements has always been allowed to be poor, and that water ingress will be dealt with when it gets to the inside of the building. This seems to no longer be acceptable.

I think that the cost of having a basement built by a contractor is going to soar due to the new B.S

[Thorfun]

I don't know about soaring prices as we had ours built from reinforced waterproof concrete with external waterproof membrane so water stopped externally. so exactly the same as it would be done under the new regulations. seems like these new regulations are to stop cowboys like @pocster doing it DIY style? 😉 

[Big Jimbo]

 

1 minute ago, Thorfun said:

I don't know about soaring prices as we had ours built from reinforced waterproof concrete with external waterproof membrane so water stopped externally. so exactly the same as it would be done under the new regulations. seems like these new regulations are to stop cowboys like @pocster doing it DIY style? 😉 

Well done. I think keeping water out has to be a lot better than sorting it out once it is in. So were your Two external methods enough, and do you put in any measures internally ?

[Mike]

1 hour ago, Big Jimbo said:

The onus now appears to be that the ingress of water should be stopped from the outside, and that the fill of any excavation should be left open untill any remedial work to prevent ingress is carried out from the outside.

Sounds OK for a detached newbuild, but can't see it working on a tight urban site or a retrofit where there is no access to the outside.

 

And, having seen a neighbour battle with builders for years before eventually having to pay another to fix the problem (it was to make additional space for his growing family - the kids had left home by the time it was fixed) I'd add internal drainage as a precaution anyway.

[Pocster]

1 hour ago, Thorfun said:

I don't know about soaring prices as we had ours built from reinforced waterproof concrete with external waterproof membrane so water stopped externally. so exactly the same as it would be done under the new regulations. seems like these new regulations are to stop cowboys like @pocster doing it DIY style? 😉 

Thanks . Myself and my architect both  agreed at that start that stopping water was difficult, managing it easier . To date ( probably 5 yrs now ) no water ingress has occurred on my diy project .

[saveasteading]

3 hours ago, Big Jimbo said:

appear that the days of letting the water in, and then dealing with it once inside might be over.

I didn't know it was ever a principle for a new basement. . Like letting a dam or swimming pool leak but catching the water!

 

It's obvious, but maybe not to the academics changing the codes.

 

I think I've only done one basement, and I had no thought of including a sump, 'just in case'.

 

 

[Thorfun]

3 hours ago, Big Jimbo said:

 

Well done. I think keeping water out has to be a lot better than sorting it out once it is in. So were your Two external methods enough, and do you put in any measures internally ?

We’ve had no water ingress through the walls or slab. No internal measures at all. The waterproofing we have comes with a 25yr warranty so I’m confident in it doing the job. 
 

interestingly the original waterproofing company we spoke to through the architects specified the internal solution that @pocsterhas and obviously works. Our architect was also ok with that solution. But the company that built our basement always used external membrane and so we changed to that. 
 

I do find it strange that new regulations don’t allow internal solutions though. As has been said in some situations external just may not be possible. 

[saveasteading]

6 minutes ago, Thorfun said:

new regulations don’t allow internal solutions though. 

Not that I have read them.. it seems obvious that a new build basement should be waterproof from outside, but that internal measures are allowed to remedy existing leaky basements.

 

Think swimming pool  and would you waterproof that on the inside:  yes of course.

 

As well as keeping the water entirely where it should be and not keeping the concrete wall and base constantly wet, there is the effect of water pressure on the membrane. The water pressure trying to force the membrane off the wall or onto it.

 

There is always a doubt that BS are not entirely logical, because the committees include proper experts but from companies with a product to sell.

 

Ask me about "Constrado" as an example if anyone is interested.

 

[oldkettle]

ICF is specifically in high risk category. Interesting. Annoying. I wonder whether my AT is aware of this, Nudura certainty didn't mention anything. 

 

I've asked to price an option with plywood internally which I saw in quite a few US videos and which does allow inspection of the completed wall. Came at twice the price. Can't say it makes much sense to me as 50 sheets of ply are not that expensive. 

Edited March 26, 2023 by oldkettle

[saveasteading]

4 hours ago, Big Jimbo said:

the cost of having a basement built by a contractor is going to soar due to the new B.S

Yes, but that is probably for the best if it prevents poor quality basements being built.

On a big site perhaps the earth is disposed of easily. But digging out town earth and dumping it in the countryside is only good for the farmer, and that only in the very short term.

I wasn't aware people were using brick or block or eps for it.  No wonder they don't work.

 

 

[George]

I haven't looked a the updated standard but my view was the preferred approach for new build was to prevent ingress with both Type A & Type B waterproofing.

[Phil Sacre]

Hi all.

 

The new standard deals with everything from convertng a little Victorian cellar to a 4+ storey deep basement structure beneath a new nuclear power station. Therefore some sifting out what suits you is required.

 

Basement waterproofing has suffered from every tradesman seeing 'internal drainage, sump and pump' on the drawings and they instantly know that if their work leaks it will have been covered over and they won't get blamed. That's how someone above paid for all the work then paid more for fixing problems. Internal drainage systems made the preceding structure workmanship worse and worse and worse.

 

The new emphasis is on keeping water out.

Yes, the tradesmen are gong to get a shock when they are dragged back a few months later to fix all their leaks before they get their final payment.

 

A new-build, single storey deep basement for a new dwelling or new extension should be built from waterproof reinforced concrete all poured and compacted with care. The concrete will be waterproof. Any cracks and voids need to be repaired.

 

The Standard says that one form of waterproofing should be continuous from the base of the basement floor slab to 150mm above outside ground level or DPC, so a narrow upstand in the waterproof reinforced concrete replacing the first course of blocks achieves that.

 

Neither beam and block, steel beams, precast planks or composite steel floors work with the upstand, so they are out.

 

ICF and twin wall (like Glatthaar Keller) are specifically mentioned in the Standard as risky because you might have to partly destroy either to find and stop leaks. (Why would you insulate both sides of a wall anyway?)

 

Sticky-back membrane on the outside seems to be assumed to not work very well either, but what it says is that a bit of membrane might cover a crack and protect that crack from leaking.

 

The term that describes concrete self healing cracks is called autogenous healing. You can look that up. Essentially, retaining walls need extra horizontal steel to restrict crack widths to what will self heal. The extra steel makes the concrete crack a lot more often but each crack is much thinner. Some unused cement grain exposed by the crack finds some unused water and they react and fill the crack with concrete.

 

It needs to be noted that one form of waterproofing is required and two are preferable. If one of those is external drainage that works by gravity and is roddable, the other need only be the concrete.

It needs to be noted that an internal drainage system, that removes water but does not stop it getting through the structure, is no longer a waterproofing option. It does not count toward your two. I would usually suggest that a bitumen based waterproof paint all over everything inside is the best second defence.

 

Phil