Finding the Level

[Barney12]

OK, so I know my slab isn't level, you only need your eyes to see that. As an example; on the large sliding door I've got 20mm difference from one end to another (over 4m). I've got 5 sets of doors with level thresholds. Huge amounts of pre-planning detail was put into ensuring the doors would sit  correctly into the slab so that the slab floor was 18mm below the FFL to allow for the tiling that is running through the entire house. 

 

I was lucky enough to be lent one of these: https://www.powertoolsuk.co.uk/bosch-gsl2set-floor-surface-lasers.html?gclid=EAIaIQobChMIuZPQ3tiI1gIV6rDtCh3uSwV-EAQYAyABEgJ3z_D_BwE so in a spare hour yesterday (whilst nursing my severe man flu, sympathy please) thought I'd have a look at "how the land lies" (quite literally! ). Its an incredible peice of kit, very clever. But alas all it did was make by brain hurt .  The floor levels run all over the place and I'm failing to see how a tiler is ever going to create the beautifully flat level access around the house which was so important to us. 

 

But im no pro tiler and so perhaps I'm just worrying too much (as we all know a self builders biggest affliction). So what now? MBC have offered to come back and level the slab but from the measurements I've taken where they will level one door they'll throw the levels out elesewhere. 

 

I was was wanting to use the laser above to gauge out the various level changes so that I got what I wanted (I'm not entirely convinced MBC have got the skill set to put this right). But with so many conflicting levels I just got myself lost. 

 

So so some specific questions:

 

1. How do you choose a rooms datum point. I assume it's normally the highest point and work out from there. Or do you just go with the middle of the room?

 

2. Can a pro tiler (like our resident @Nickfromwales) "loose" these level changes? Presumably by feathering out across as big a distance as possible?

 

3. Is it sometimes better just to grind off an area of high spot? Presumably there are tools for the job that are designed to do this and get into corners? (Without trashing my expensive frames!).

 

Many thanks in advance. 

Edited September 3, 2017 by Barney12
Typos

[Nickfromwales]

@Barney12

Ok, just to better grasp this. 

Your rooms are to be tiled through from one space to another, room to room, seamlessly? Does the tiled floor run past several external / folding door thresholds, and have you established that all the door thresholds are all exactly the same level off a datum you've fired through the floor space ?

Do you have a flor plan you can post with an example of where the tiled floor starts and finishes ? Saves a lot of typing. . 

[Jeremy Harris]

Our tiler spent around 40 minutes or so trying to find the highest point on the continuously tiled area to use as the starting point.  The idea was he would work from there, and if any areas were beyond the tolerance he could take up with adhesive then some levelling compound would be use to bring them up to within tiling tolerance.

 

We were lucky, our slab was dead flat, so flat that we had loads of tile adhesive left over (around eight, 20kg bags, IIRC).  I think that the adhesive can make up for something like a 6mm discrepancy, any more than that and you need to level things out first.  @Nickfromwales is the guru, though, and will correct me if I've got this wrong.

[Nickfromwales]

I've taken as much as a half inch with adhesive, but then I was getting 3-4 600x600 tiles laid from one 20kg bag. At that stage I stopped and chucked some self leveller down ready for the next lot of tiles to go down as it was getting silly. Popped the laser up and showed the customer the floor ran out 15mm from one end of the kitchen diner to the other, about 5.5m. Got just over half way before I stopped laying and levelling as I went with adhesive.

I kept the floor running flat as a mill pond as I was running past the sliding doors to their conservatory and wanted to give a flush finish to that threshold. The floor was partially raised with insulation boards, for UTH, so the final levelling was just to raise the 15mm I simply hadn't seen to level, ( the builder who did the knock-through self levelled the whole area before my arrival, but just made it smooth not level  my mistake for assuming it was done properly ).

 

We really need to establish where this floor runs out in relation to reference points such as sliding doors and internal door thresholds etc before commenting further. 

 

Edit to add : the above floor could have followed the subfloor and just have had half of the undulation taken out if it want for the sliding doors, so only 7.5mm taken out rather than the full 15mm for eg.

Edited September 3, 2017 by Nickfromwales

[Barney12]

OK, thanks. I'll use the internal door threshold and the external door thresholds as my datum markers. 

Ill see if I can sketch up a plan.

[Barney12]

42 minutes ago, Nickfromwales said:

@Barney12

Ok, just to better grasp this. 

Your rooms are to be tiled through from one space to another, room to room, seamlessly? Does the tiled floor run past several external / folding door thresholds, and have you established that all the door thresholds are all exactly the same level off a datum you've fired through the floor space ?

Do you have a flor plan you can post with an example of where the tiled floor starts and finishes ? Saves a lot of typing. . 

 

Sorry only just seen this earlier reply. I'll post something up shortly.

[Nickfromwales]

Add as much info as you can. ?

[Barney12]

OK, so here's a floor plan:

 

We have a split level slab which I've denoted with a dotted line. The higher section (right) concerns me less.

I've marked the height difference points by the silder. At this point the slab is roughly 18mm as required. It then drops to c35mm at the other end.

I've noted your comment about needing to see if all the door thresholds are at the same height. I'll try and do that tomorrow.

Edited September 3, 2017 by Barney12

[Nickfromwales]

Ok. I'll open that on the iPad later when you've updated the info ?

[Barney12]

3 minutes ago, Nickfromwales said:

Ok. I'll open that on the iPad later when you've updated the info ?

 

Tis up. Ta for reviewing

[Nickfromwales]

Ok, so is this contained to one room if only one is marked or will it also need to match in the kitchen diner? Are the kitchen diner thresholds level with the one marked ?

[lizzie]

Following  with interest Barney.......we also have a very bumpy slab, judging by ours I dont think when they lay it they 'level' they just smooth it out. I have no expererience of this so I presumed that was the norm and we are left to try and get it flat afterwards.

 

It is a concern for us too as we are about to take delivery of Internorm level threshold sliders and we are tiling the whole house with 600x600 porcelain.

 

Slab is up and down like the hills around us god knows how the tiler is going to cope but he has seen it so we have to hope he can sort it out without too much hassle or extra expense. We are going for the ditra matting as well as whatever adhesive/levellers needed as ditra may help in getting it flat.

 

 We have also had to compensate for dips in the flat deck roof boards above (we are single storey)  - most noticeably in the area near one major dip in the floor slab so it may also be that the internal frame is a bit lop sided around the big slab dips. I have not checked it  but it looks a bit that way as was really highlighted by the water that collected in those areas.  Hopefully all will look straight when boarded and plastered.

 

 Thank goodness we have a fantastic carpenter who has been able to 'straighten' it up externally by compensating to lose the dips  when putting our roof on top so the pond is gone and the roof drains and the fascias are all level and not up and down like a big dipper!

 

 

[Barney12]

8 minutes ago, Nickfromwales said:

Ok, so is this contained to one room if only one is marked or will it also need to match in the kitchen diner? Are the kitchen diner thresholds level with the one marked ?

 

The big double doors between the lounge and the kitchen/dinner will remain open almost all of the time so the idea was this was all on the same level with no threshold to create feeling of space.

I haven't checked the levels of all three but will tomorrow.

[Barney12]

6 minutes ago, lizzie said:

 

 

It is a concern for us too as we are about to take delivery of Internorm level threshold sliders and we are tiling the whole house with 600x600 porcelain.

 

 

Check and triple check your FFL whilst they are installing. Unfortunately for us the Internorm fitters were able to clearly demonstrate the slab and in some instances frame was out of square. From that point forward they were rather "not our problem guv".

 

Our first floor slopes a good 20mm, enough to be noticeable when you walk on it. MBC are having to screed that too.

 

We've also got a lot of packing to do to get heads level etc.

 

Our dormer walls are out of square by 25mm across 3m. When cladding externally I had to double batten by the time I got to the other end so that it was square. The internal battens have also been packed to get it square.

 

As I've said before I do rate MBC highly and they have been very receptive to problems. However, you can be fooled into thinking they produce a perfect product if you read this forum and the old eBuild. For the inexperienced that's a dangerous trap and in some ways actually is to their disadvantage as peoples expectations are too high. Building is an imperfect science and the key guys at MBC are so stretched that they appear to be increasing reliance on sub-contract trades. Growing pains are the peril of many a company!

[lizzie]

3 hours ago, Barney12 said:

 

Check and triple check your FFL whilst they are installing. Unfortunately for us the Internorm fitters were able to clearly demonstrate the slab and in some instances frame was out of square. From that point forward they were rather "not our problem guv".

 

 

Thank you we will have some of that packing and rectifying to do I'm sure.

 

Wish I had known all this when it was being done I would have mentioned the dips!  Some trepidation now about sliders, windows didnt matter as they are off the floor.  Thursday is D day for sliders.......better get over there with bacon sarnies and sweet smiles for the fitters and hope for the best!

[Jeremy Harris]

3 hours ago, Barney12 said:

 

As I've said before I do rate MBC highly and they have been very receptive to problems. However, you can be fooled into thinking they produce a perfect product if you read this forum and the old eBuild. For the inexperienced that's a dangerous trap and in some ways actually is to their disadvantage as peoples expectations are too high. Building is an imperfect science and the key guys at MBC are so stretched that they appear to be increasing reliance on sub-contract trades. Growing pains are the peril of many a company!

 

I think you've hit the nail fairly and squarely on the head here.  I'm probably one of those who have raised expectation levels, as one of the first here to use MBC (there were actually two of us that were first, but Greg doesn't seem to have followed us over from Ebuild).  Anyone that's read our blog will have read that I was very impressed with the effort taken to get the foundation base and slab dead level and flat, and will also have read about the savings we then had as a consequence of that, everything from using far less plasterboard because the walls and ceilings were all dead square, to using far less tile adhesive because the slab was so flat and level.

 

This was down to the expertise of the key guys, I know.  We had Brendan full time on our build, and he is fanatical about getting things right.  I remember asking him why they were taking so much time to get the grit blinding dead level and flat before putting down the slab insulation, and him saying that they'd learned that time spent getting this flat and level was time saved when they came to stand the frame up and get that level and square.

 

Training new people takes time, and the best guys cannot be on every build all the time, so I guess it is just "growing pains", as skills are built up to the "Brendan level".

[dogman]

I was talking to MBC when they were with me a few weeks ago, and they told me that they have employed a new member of staff to quality assure the work of the contractors. I had a company that had done two or three for MBC and most issues i had were related to their work. That said all my issues were simple to fix. 

[Oz07]

Was @JSHarris slab not power floated?

 

From the sounds of it the two latest slabs haven't been?

Has this been dropped from the spec or is it an 'extra' within the package?

 

I usually use a self compacting concrete which with not much skill you can get to within 10mm. Dare say tighter tolerance if you spend a little more time and effort on it.

[Barney12]

2 minutes ago, Oz07 said:

Was @JSHarris slab not power floated?

 

From the sounds of it the two latest slabs haven't been?

Has this been dropped from the spec or is it an 'extra' within the package?

 

I usually use a self compacting concrete which with not much skill you can get to within 10mm. Dare say tighter tolerance if you spend a little more time and effort on it.

 

Yes, ours was power floated.

[Oz07]

hmm perhaps the change in level doesn't help in gauging a flat slab but still disappointing. Perhaps MBC should consider self compacting concrete if struggling with skills shortage?

[TerryE]

@Barney12 It sounds like MBC have got real quality issues with one of their foundation / slab crews.  In our case they were very particular about getting the entire site level at each compaction layer as well as at the sand base and the formwork before they started the pour.  We later found a slight low point in one room (about 4mm in a 6.5 m span), that they missed during floating.

 

We didn't have Brendan, but his #2 Mick.  I asked  Mick why they were so particular about the layered compaction, and he said that the main risk with this type of slab was differential settlement across the slab if the underlying ground or the layering / compaction across the area wasn't uniform and this could lead to local slumping across the slab before it properly started to cure. 

 

If they did the same on your slab, I  can't see them getting the concrete levels out by 20mm.  Do you think that it could have been differential settlement?  Even so the right thing to do would have been to fix it by levelling before doing starting the frame.  And the framing crew should have highlighted this issue.  Not good.

   

Edited September 3, 2017 by TerryE
Slight clarfication of wording

[Jeremy Harris]

32 minutes ago, Oz07 said:

Was @JSHarris slab not power floated?

 

Yes, it was power floated, in the main, but because the concrete was delivered late (a pretty familiar tale, I'm sure........) the final finish was by hand, out of deference to the neighbours at around 10pm.

[ToughButterCup]

2 minutes ago, TerryE said:

 

[...]

Even so the right thing to do would have been to fix it by levelling before doing starting the frame.  And the framing crew should have highlighted this issue.  Not good.

 

I have found that there is a huge pressure to 'get on' when a new crew arrives on site. The arrival represents a long-hoped-for, long-planned-for  next step, and so it takes huge courage  to call for an unplanned pause before the next phase of the build. All sorts of arrangements have to be remade and who knows what sort of mess ups that process will cause.

 

I deeply sympathise with you @Barney12, 12mm here and 25mm there are not trivial amounts: it must feel like a  dead  weight dragging  your project back, causing lost sleep  and added expense. And not a little irritation. 

 

I have yet to examine our slab in any great detail  .....

[Barney12]

Our initial slab work was subcontracted to someone (called Matt) who then subcontracted it (from what I could gather).

To be frank the initial guy onsite (with his son) didn't seem to have any experience and did little to fill me with confidence, in fact his attitude was very poor. Brendan and his crew did arrive later on in the work as they were falling behind. But, as seems to be the case with Brendan (and Darren) they would arrive one day and be gone the next as they juggled multiple jobs. 

 

In fairness (although still MBC's error) our problems were compounded by the timber frame designer (again a subcontracted element not an employee of MBC) getting the frame detail wrong and the initial slab crew cocking up the recesses that the window/door frames were designed to fit in. There was much remediation with a grinder and bolster chisel !!! 

 

As ive already said though MBC have been very helpful in putting things right. I just hope that we get the floor we want  

[Barney12]

2 minutes ago, recoveringacademic said:

 

I deeply sympathise with you @Barney12, 12mm here and 25mm there are not trivial amounts: it must feel like a  dead  weight dragging  your project back, causing lost sleep  and added expense. And not a little irritation. 

 

 

Ive done a few properties over the years (actually I've never bought a habitable house!), mainly refirbs but also a barn conversion and an almost complete rebuild (we left a couple of walls standing!). All have been 'traditional' in construction which I personally have found much simpler to control as the speed is slower.

 

I dont think i'll build another passive slab and timber frame. The experience has been far from enjoyable. I'm going to be elated when these issues are finally resolved. I can then get on with what I enjoy most with is the internal elements of a build, I guess it's where I'm most comfortable. 

 

Actually im not sure I'll ever do a project of this scale and complexity again. Oh and definitely not on a National Park. Oh and I'm looking for bats in anything I ever buy again. So much as a dropping and I'm walking away