Gottcha! .... about two years too late....

[ToughButterCup]

But never mind I haven't paid the bill yet.... (despite having followed proper procedure)

 

I have a strange feeling that Aesop is sitting on my shoulder. Bless 'im! 

This is my fault; naivety coupled with just enough money, and a general bias towards optimism. 

 

Let me tell you a story. Sitting comfortably? Then I'll begin.

 

Our house is built using Durisol. Cheap, cheerful, targeted at noobies like us. Common on GD. Good U value, easy to handle yadda yadda yadda. 

By a quirk of fate  (the Planners asked us to chop the front of the house off), part of the insulated front of the house is inside the house. In other words, inside the heated envelope.

 

Well ! Guess what! I had a brainwave (can you hear the punch-line building yet?)

Don't need the insulation inside the house? Well, chop it out then!  Yo Sushi ! Go Team Salamander !

 

Check with the manufacturers, and the SE (very nice man, very very nice man haven't had his bill yet), it's all OK.

@Stones came by and marvelled, @ProDave came by and marvelled. Look ! part of a structural wall cut out  and no need for a lintel. 

 

Bit like   Look mum, no nickers!   Ya should have seen their faces: polite concern writ large.

 

Any road up, SWMBO soon had  an idea for  the space freed up. And off I went happy as a sand boy to dig the insulation out.

Now then boys and girls, look at this , and what do you see? I mean, beyond  a Teutonic propensity for taking the wall to bits in neat squares ?

 

I've dug out two columns of blocks (the equivalent of one Durisol block) exposing the concrete behind, and cut off only the face of two blocks  (LHS) exposing the insulation.

 

So far so good.  Now look at this ...  Look at the bottom right hand column

 

Yep, insulation missing. Had I taken it out?  - Nope.

 

I'm exposing (cutting the face and insulation off) about 2 full square meters of wall. And so far found four instances of this little piece of laziness.

 

Duplicate that randomly over the whole house and ..... ?

 

Look on the bright side Ian !  You'll know what to do when the black mould spot pops its ugly fizzog  on the wall inside the house.  

 

6mm SDS , 300 mm long , squirt squirty with my new-found tool of choice. Insulation foam.

 

Ahhh, isn't that nice children? If it you do it all yourself, you know how to sort out cock-ups. 

Now then,  sit up straight and let's see who can go home early !

 

Not you @Nickfromwales, I want to see you when everyone's gone. .... Again.

 

 

 

 

[MikeSharp01]

Sorry what was the question again?

[MikeSharp01]

Is it about extrapolation or some such? Cos you know that correlation does not mean ..... 

[Lesgrandepotato]

I suspect it’ll be absolutely fine. 

[Lesgrandepotato]

So looking at that it’s about 100mm of celotex? Where it’s minimised you are down to perhaps 70mm. 
that’s still a comfy 10mm over what we have everywhere in our build. 
I’d hazard it’s designed to be laid ‘agriculturally’ and still work to spec. If it didn’t it’d be all over the place. 

[ToughButterCup]

37 minutes ago, Lesgrandepotato said:

So looking at that it’s about 100mm of celotex? Where it’s minimised you are down to perhaps 70mm. 
[...]

 

200mm of Celotex; 

Perhaps 70mm?  

It's 0. Zero, zilch, nugatory, nada, nichts, rien. Proper cold spot. @TerryE would blow a fuse, and Mr Harris would sue everyone in sight if someone had done that on his build.

 

 

However, you are right when you say

40 minutes ago, Lesgrandepotato said:

[...]
I’d hazard it’s designed to be laid ‘agriculturally’ and still work to spec. If it didn’t it’d be all over the place. 

 

The aggregate is 10mm in a sloppy (scotch-broth) slump. It's amazing how effective that bit of stone is at stopping the flow of pumped concrete.

[Jeremy Harris]

I'm having trouble visualising this (my fault, not at all familiar with the way Durisol blocks are made up).  The problem seems to be that gap at the lower right, which is indicative of other, similar, gaps elsewhere.  So, is it that the gap extends right through the wall, from the internal face to the external face?

 

From the photo, it looks as if alternate courses of blocks are laid as stretcher bond, so the insulation blocks don't align.  It also looks as if it's the wood/cement fibre bit that's missing, rather than the PIR foam bit (I may well have got that wrong).

 

Any chance of a rough sketch to help understand what's going on?

[ToughButterCup]

2 minutes ago, Jeremy Harris said:

[...] 

So, is it that the gap extends right through the wall, from the internal face to the external face?

[...]

 

No, the gap stops at the concrete. The wall is still solid concrete.

A Dursiol block - imagine a block in plan, 500 wide, 365 deep, the front 220mm is insulation, the rear 100+ is concrete. The balance is the wood-based form encased in Portland cement.

Sometimes, when blocks need to be cut (because the wall is not an exact multiple of 500) small bits of insulation need to be cut to fit the cut block.

 

Or not fitted into the cut block as the case may be.

7 minutes ago, Jeremy Harris said:

[...]

It also looks as if it's the wood/cement fibre bit that's missing, rather than the PIR foam bit (I may well have got that wrong).

[...]

 

I did a double take myself. No, its definitely the insulation missing. In four places that I have dsicovered so far.

Bless 'em, they couldn't have given a stuff: and while inside the heated envelope it doesn't matter. But, as I say, when (if ever) little black mould blobs occur, it'll be out with the SDS, quick look with the camera, and a squirt of foam.

 

Here's hoping that its only happened four times .... ?

 

[Jeremy Harris]

Gotcha, I was struggling to see how things went together.  Does seem like a bit of squirty foam will fix any holes you find.  These voids will be pretty well sealed up, though,  and being relatively narrow may not be as bad as you think. 

[ToughButterCup]

What are the chances that I would discover the omission?

[daiking]

?‍♂️ Worse things happen at sea.

 

I bet you could find loads in future with a thermal camera but really, do you honestly expect to find mouldy spots in an otherwise hi spec build?

 

i don’t get mould in a plasterboard tent with rain dripping down the exterior walls.

Edited November 5, 2019 by daiking

[ToughButterCup]

Hmmm, yer right ... next thing that @Russell griffiths will be along and tell me that I'm over-thinking it again.

[daiking]

1 minute ago, AnonymousBosch said:

Hmmm, yer right ... next thing that @Russell griffiths will be along and tell me that I'm over-thinking it again.

you now know the builders weren’t what you thought they were at the time. Not your fault. (I’m not one for victim shaming)

 

even if it’s not 100% of what it should have been, 80% of that is still so much better than the alternative. These things are now just your way of punishing yourself for what happened in the past. They shouldn’t be.

[ToughButterCup]

4 minutes ago, daiking said:

[...]your way of punishing yourself for what happened in the past. They shouldn’t be.

 

Thanks... I'm well beyond punishing myself. Thats long gone - firmly in the past.

I posted this thread because I thought there might be some mileage for those early on in their build :

 

I hope that this thread might be seen as a wry look at a bit of a cockup, and how, even when it does prove to be one, then there are normally  ways round the problem.

A few years ago, I would have gone into a proper Teutonic strop about it. Not any more.

[Russell griffiths]

I was sitting here trying to be quiet. 

[ToughButterCup]

12 minutes ago, Russell griffiths said:

I was sitting here trying to be quiet. 

 

Phhhhhhhhhh. ?

[TerryE]

Ian,  I think this is almost certainly one for being a little sanguine.

 

20 hours ago, AnonymousBosch said:

A Dursiol block - imagine a block in plan, 500 wide, 365 deep, the front 220mm is insulation, the rear 100+ is concrete. The balance is the wood-based form encased in Portland cement.

 

The failure case here is that the front 220mm is an airgap.  If these are occasional and isolated, then the overall impact on U-values should be small.  I though that the 175×185×250mm PIR inserts were factory installed.  Is this not the case? Or were you relying on your contractor to insert these during erection?  If this is an occasional issue, then the voids will be isolated so you won't be experiencing significant convection elevators in the void columns.  If we do a back-of-the fag packet calc of the U-values of (i) the proper profile and (ii) the voided profile, hen we can come up with a realistic guess to the failure %.  The net U-value is roughly the prorated value, e.g. if you reckon 10% then its 0.9×U₁+0.1×U₂.  And you will see that this is extremely annoying but isn't that material.

 

Cast you mind back to erection.  You were hovering during this.  You also had a wall blow over.  Surely you would have noticed an excess of PIR inserts floating around the site if they weren't being installed?  One possible scenario comes to mind is that there were a number of blocks that had the PIR missing or dropped out and one good place to use them up is on an internal wall where the insulation isn't needed.

 

If you are still concerned and want to get a better view on whether this is a significant issue, then one option would be to try some pilot holes to get  a statistical sample.  OK, this involves drilling into the wall from the outside with a 60cm×15mm drill (or whatever you use to pilot holes through the wall fabric) to probe the void / PIR, and you will only want to try this where you can repair / make good the holes afterwards.  But if you do 10 holes, say, and 10 go into PIR then I'd forget the issue.  If you get one void then your might want to survey a little more, 2 or more then I'd be concerned.

[SteamyTea]

Slovin's Formula

 

n=N÷(1+Ne²)

n = number of samples

N = total population

e = error tolerance

 

Now you should know how many block you have, and taking @TerryE idea about tolerance on the U-Value, you can set your tolerance level.

 

Make up formula in Excel of x and y values, where x is the number of blocks long, y is the number high, then assign a random number to each.

That is then the position where you need to sample.  Avoid any duplicates, but do not avoid adjacent blocks.

 

=randbetween(1,x)

=randbetween(1,y)

 

Easy and interesting

Edited November 6, 2019 by SteamyTea

[joe90]

On 05/11/2019 at 11:18, AnonymousBosch said:

But never mind I haven't paid the bill yet.... (despite having followed proper procedure)

 

Why not take a photo of the missing bit and use it as a lever to get a bit of discount on the price and say your not convinced there is more missing!

[ToughButterCup]

17 hours ago, SteamyTea said:

[...]

Easy and interesting

 

Indeed, thanks very much @SteamyTea . I'm almost feeling like getting the calculation done and then the drill out .

 

But @Russell griffiths would laugh at me, @Construction Channel would roll his eyes, @Nickfromwales would tell me to get on with the plumbing, @Jeremy Harris would point out some fundamental errors, @TerryE would point out some rare statistical anomaly that occurs in months where there is a Friday the 13th, @MikeSharp01 would keep winding me up about the size of my drill - it's the diameter that counts , and @Pete would bring a deck chair to watch. 

 

So @SteamyTea, I think I'll pass on his one, ta!

[Russell griffiths]

Only in a friendly manner I must add. 

[Nickfromwales]

Get on with the..........