Structural walls in the middle of my B&B floor

[Tony L]

My foundation plan looks like this:

 

The two piers that are right in the middle (I’ve drawn a purple ellipse over one of them) are there so the entrance  hall (in the middle at the bottom of the picture) will be open plan onto the kitchen, which is in the middle at the top of the picture.  I envisaged 100mm wide concrete block piers being built up off the top of the poured concrete foundation (where the piers are) all the way up to the RSJ that will support the side of the landing that overlooks the galleried entrance hall. The top of the stairs may also be supported on this RSJ.

[Tony L]

 

My B&B floor is more than half complete.  Over the weekend I made a site inspection & I can see that the B&B floor has just been put over the top of these two foundation piers.  In the picture below, there’s a gap of several cm between the beam, which is off the right edge of the sleeper wall underneath, & the sleeper wall below.

[Tony L]

I can’t see what’s going on on the other pier because all I see is B&B covering it.  I’m surprised to see it being built like this.  Perhaps the builder will remove the blocks & build up under them, so the blocks are supported, on top of the foundation.

 

If that’s his plan, what do I do about mitigating cold bridge?  Do I stick some Marmox blocks in somewhere?  Where?  I don’t know much about these. I need to learn.

 

The sleeper wall within the green ellipse at the bottom of the picture is intended to support a wall that will come up about 1m above FFL & support one side of a landing just under half way up the stairs. So this wall will be supporting the staggered ends of short beams.  Presumably, I can build my 1m high by 100mm wide wall, to support one side of the 180 degree turn landing, from concrete blocks, directly on top of the beams.

 

Do I need to worry about cold bridge here?  The beams are resting on aerated trench blocks, so not as bad for cold bridging as would be the case if they were resting on regular 100mm concrete blocks.

 

[ProDave]

As per the other thread (broken blocks) it is time to have a chat with the builders, to build up under these piers that are there for a reason, and replace the broken blocks.

 

It is a good job you are keeping an eye on them, though a shame they are not doing it right without you prompting them.

[Tony L]

3 hours ago, ProDave said:

... build up under these piers that are there for a reason, and replace the broken blocks.

 

Thanks, @ProDave.   Is it best to use bricks or cuts from 7N blocks with max. 10mm mortar above & below to create this "build up"?  Then, presumably, we can continue the wall upwards with 7N dense blocks sitting on top of the section of the B&B that's supported underneath by the piers - so this wall will cut through the insulated floor.

 

Should a special brick/block be used for the first course that sits on top of the B&B?  This first course of internal wall is going to have the floor insulation either side.  I'm thinking if we just go up with regular blocks, there will be a cold bridge.

[dpmiller]

would it not work better if the blocks were lifted and the middle beam in the photo moved leftwards so the "landscape" blocks were to the right of it?

[saveasteading]

The piers have to be directly on the foundations.

It all seems worryingly vague, and that you are your builder think this can be made up as you ho along.

Is there a design for the piers and the beams?

[joe90]

2 hours ago, saveasteading said:

It all seems worryingly vague, and that you are your builder think this can be made up as you ho along.

Is there a design for the piers and the beams?

This is why I always go full plans, no making it up as you go along. Good for you for checking and you need a serious chat with your builder.

[Mike]

2 hours ago, saveasteading said:

Is there a design for the piers and the beams?

This.

 

The floor supplier should have been sent drawings showing the foundation & the position of the piers, and the supplier should have sent back a plan showing where each beam should be positioned. And your contractor should be following that plan.

[saveasteading]

As I often say on BH.

The bco is not your designer or to be relied upon to spot everything. But in this case perhaps ask them along.

If you have a designer of any sort, get them to sort this out. Meanwhile stop the work...that is sensible but also concentrates the builder's mind.

Let's hope the builder is just going about it in an odd order.

[Russell griffiths]

I said it before

going to say it again 

you need to stop work and get a set of drawings showing what you are actually building 

you should have a block n beam diagram showing the location of all the beams, they should have been designed to allow any load bearing walls to come up and through the floor. 
they will also have been designed to avoid any soil pipes coming upwards. 
I think a bit of cold bridging is the least of your problems 

stop now make a plan and work to it, or charge on with no plans and find out what sort of cock up you end up with. 

[Tony L]

11 hours ago, dpmiller said:

would it not work better if the blocks were lifted and the middle beam in the photo moved leftwards so the "landscape" blocks were to the right of it?

Thanks for the suggestion, @dpmiller.  I’m definitely not the right person to answer this question – I suppose I can see what you suggest would make sense, if the correct way to build my pier walls, for the ends of the FFL RSJ to sit on, is to build up under the beam (& probably the blocks to either side?) so we end up with a seamless B&B floor, & the builder marks the beam & we measure from the inner wall so we know which beam to build the pier wall off.

 

Another way of doing it might be to build up the piers directly off the poured concrete in the trench, so I have a 100mm wide pier wall made from concrete blocks in their usual upright orientation (215mm high) & this wall would penetrate the B&B floor – then, presumably, there would need to be a beam either side of the pier wall.  I’m not sure if this is what you are suggesting, @sas

 

I welcome opinions (or better still, facts), on these two options or a better way of building, please.

 

I will see what I can learn from any more responses that may come in this evening/tomorrow then I will ask my SE about this.  Of all the people I’ve got working on the project, he’s the only one in whom I have 100% confidence.

[Tony L]

10 hours ago, saveasteading said:

The piers have to be directly on the foundations.

It all seems worryingly vague, and that you are your builder think this can be made up as you ho along.

Is there a design for the piers and the beams?

Your criticism of my way of going about this is fair.  I didn’t intend to be helping the builder make it up as we went along.  My understanding was,  there is a well established best method for dealing with piers such as these, & the builder would know exactly what to do.  The builder had not told me, "There is detail missing from the drawings.", & he assured me, he knew exactly what to do with regard to all aspects of the work I’d commissioned, even telling me this is small fry for him & he usually deals with much bigger, more complex projects.

 

The drawings he has are the SE’s drawing at the top of this thread & the drawing below, which was on the side of the SE’s drawing, ie the same sheet – this shows the beams at an outer wall, so it doesn’t help with the piers, & in any case, as I reported in my trench blocks thread, the builder didn’t build to match the drawings; he decided on a different solution, without even explaining this to me until I pointed out that what I could see he had built, did not match the drawings.

 

The builder also has two versions of the 2^nd drawing below.  He has two versions, because after I gave him this drawing, & after he’d passed it onto the beam company so they could quote the beams, I noticed there were errors on the drawing (the beam co. had provided a quote, having not noticed the dim.s didn’t add up properly).  The arch tec didn’t want to correct his drawing (let’s not get side tracked by that story, but I will just say, he's even worse at his job than the builder), so I made corrections to his drawing myself, showing less detail (I took off elements the beam company wouldn’t need, to make things clearer for them) & correct dimensions (dims were one of the things the arch tech had got wrong).  I should just point out, all the beams run left right across the house - just ignore the part of the drawing where the arch tec has got them going up & down (I had to tell him to correct this on 3 versions of this drawing before he got it right).

 

To answer your question re B&B design: yes, I suppose the beam company would have produced a design for the builder to work from, but I haven’t seen this drawing; it was only when I read your post that it occurred to me this is the way this ought to work – I’d been thinking a load of beams would be delivered – so many of each length, & it would be obvious where they’d go from the SE drawing.

[ProDave]

I am confused.  your other posts about issues with the builder showed snippets of drawings showing how it was supposed to be done compared to pictures of how the builder did it.  From that I assumed you had full drawings and the builder was not building to the drawings.

 

Are you now saying a full set of detailed drawings does not exist?  That would certainly put a different perspective on the issue?

[Tony L]

7 hours ago, joe90 said:

This is why I always go full plans, no making it up as you go along. Good for you for checking and you need a serious chat with your builder.

I’ve paid for a full plans approval, but because we anticipated difficult ground conditions later in the year, I agreed with BC, we were going to do the digging & get up to the B&B level before winter came, then complete the drawings & get these approved before any more work is done.  This plan has not worked well, & I hope others will benefit from my explanation of how badly things are working out for me.

 

I have already had one "serious chat" with him, & from a week ago he has been receiving emails from me, gently reminding him of his shortcomings, & suggesting a better way of working together.

[Tony L]

4 minutes ago, ProDave said:

I am confused.  your other posts about issues with the builder showed snippets of drawings showing how it was supposed to be done compared to pictures of how the builder did it.  From that I assumed you had full drawings and the builder was not building to the drawings.

 

Are you now saying a full set of detailed drawings does not exist?  That would certainly put a different perspective on the issue?

I don't think I'm now saying anything that contradicts anything I have posted since I joined the forum.  I have some drawings.  The builder has all the drawings I've posted & more.  I understood the drawings to be full & sufficiently detailed for all the work the builder has been asked to do (build up to B&B level).   I'm a complete novice so inevitably I've got some things wrong. Every time somebody tells me I'm doing something wrong, & tells me what to do instead, I am grateful.  I've got drawings for the rest of the work (ie full house build), but these are not yet finalised & much work will be required on the detail before they can be considered full & complete.

[Tony L]

1 hour ago, Russell griffiths said:

I said it before

going to say it again 

you need to stop work and get a set of drawings showing what you are actually building 

you should have a block n beam diagram showing the location of all the beams, they should have been designed to allow any load bearing walls to come up and through the floor. 
they will also have been designed to avoid any soil pipes coming upwards. 
I think a bit of cold bridging is the least of your problems 

stop now make a plan and work to it, or charge on with no plans and find out what sort of cock up you end up with. 

Thanks @Russell griffiths.  I will ask my builder for the B&B plan so I can see if what he's built matches the drawing.  I'm assuming the company that is supplying the beams will have drawn this - is that right?  Should my arch tec have drawn this (he didn't)?  This would make more sense to me, because the arch tec knows what's going on up above the B&B.

 

Should there have been a section drawing for the piers, similar to my SE's "Typical Section" drawing, above?  Does anybody have a drawing they could show me, please?  Does anybody have a photo of this type of internal structural wall that comes through the B&B floor?

 

My understanding now is: these piers should be built up as a wall, built from 100mm wide & 215mm high concrete blocks.  The wall should start on the poured concrete in my trenches & come straight up through the B&B slab, so what my builder has built must be incorrect, because what he's built just looks like B&B floor over the top of the foundation slab piers; the advice I was given above, regarding building up from the foundation so the B&B floor is supported in the zone where the wall supporting the RSJ is, is incorrect.

[joe90]

Your architect will draw the plans and a copy goes to the B+B supplier so thst everything  fits.

[Canski]

19 minutes ago, Tony L said:

I'm assuming the company that is supplying the beams will have drawn this - is that right?

This is correct. I hope that the beam and block company had the drawing that showed the walls below DPC ( foundation plan) 

the blockwork should be built to the underside of beams then a full DPC added before laying the beams to the plan supplied by the beam and block supplier. Then prior to the blocks being suspended in the beams the 50 mm or so should be built up solid to the underside of the blocks and then the blocks inserted. 

[Mike]

14 minutes ago, Tony L said:

My understanding now is: these piers should be built up as a wall, built from 100mm wide & 215mm high concrete blocks.  The wall should start on the poured concrete in my trenches & come straight up through the B&B slab

You've got it :)

 

15 minutes ago, Tony L said:

Should there have been a section drawing for the piers, similar to my SE's "Typical Section" drawing, above?

Unlikely - it's a standard construction.

[Tony L]

10 minutes ago, Mike said:

You've got it

 

Unlikely - it's a standard construction.

Well it's good to know I'm not missing a section drawing for this detail, thanks @Mike.

 

There's no BH consensus.  I'm being told this should be done two different ways: 1) build up through the B&B. 2) Support the B&B properly & build on top of it (& thanks for the reminder to check full DPC coverage for this method, @Canski). I think the first method sounds best, but given I didn't know as much about this yesterday as I do now, & also the builder wasn't given specific instructions, I think so long as he has properly built one or the other method (which he certainly hadn't done yesterday), that's what I'll have to have.  I'll go to the site & see what's going on tomorrow morning.  I may tell him to stop work, but there's nothing going on top of the blocks, anyway, so I don't think going to make things any worse, & there could be plenty of unrelated tasks he can keep going on, such as there's a big sectional IC to install where the connection to the main sewer is.

 

I've found a drawing which supports method 2), support B&B & build on top, but this is different from my situation, because there's a change of direction for the beams & the wall in the diagram, below, is sitting on top of several beam ends; if I have my wall on top of a beam running lengthways, this isn't such a good solution because of the tiny curvature built into the beams.

 

[Mike]

5 minutes ago, Tony L said:

I'm being told this should be done two different ways: 1) build up through the B&B. 2) Support the B&B properly & build on top of it

• A non load bearing block partition can be built on top of a beam & block floor if the floor designer has taken the loads into account in the design (often requiring extra beams)
• A load bearing wall can't be built off a beam & block floor because the loads would (normally) be too great
• A beam & block floor can be built a load bearing wall and be supported by it (i.e. the wall is supporting the floor, not the other way round).

Your builders seem to be making a sandwich of a wall that's vaguely attempting to support a floor that's supporting a wall, which isn't acceptable.

[Tony L]

Thanks, @Mike, but I'm not sure exactly what it is you're telling me to do/not do.

 

I went to the site yesterday & one end of one of the piers didn't yet have a block fitted over it to make the BB floor flush where it covers the pier underneath.  I could see DPC & mortar & what the builder called "biscuits" - little mini concrete blocks - "brick slips", I suppose, although I thought brick slips were something else.  The poured concrete pier had been built up with trench blocks and/or regular blocks laid flat.  There's damp course covering this (I saw one end, anyway) & the builder says he's built up the last (200mm, approx) with brick slips & mortar, to support the beam & blocks, & we can continue up with blocks on top of this (to support the RSJ) - this plan has all been discussed with my SE, I should add.

 

I'd really like to go there with a builder I trust more than this one, & pull up the blocks either side & have a look.  Would this be easy enough to do?  I'm guessing I'd have to start pulling blocks up from an edge & work all the way to the middle before I could move the blocks that are next to the pier.

 

@Russell griffiths.  Thanks - I now have the beam plan, which was drawn by the company that supplied the beams.  It looks like the builder has followed this.  A beam sits off one edge of the pier beneath.  I've had a good look & I can't find any pictures or 3D diagrams on line of a wall coming up & through the floor.  I'm still keen to see this arrangement if anybody had such a picture/diagram, please.  I've been very busy at work the past 2 days (still at my office at 11pm, now), so I haven't had a chance to ask my SE about all this yet, but I will.

[Mike]

22 hours ago, Tony L said:

Thanks, @Mike, but I'm not sure exactly what it is you're telling me to do/not do.

Maybe you can spot the problem from these sketches? This is a vertical section, with the foundation at the bottom.

 

What you appear to have is something like the one on the left. What you should have is the one on the right, or some other variation that supports the load bearing wall right down to the foundation.

 

 

 

[Canski]

18 hours ago, Mike said:

What you should have is the one on the right, or some other variation that supports the load bearing wall right down to the foundation.

No no no. Don't build anything different than what is on the beam and block drawing. Every action has a reaction and if you don't follow the beam and block drawing you may discover this first when you come to a S&VP.  If you have a situation like the section on the left simply lay the DPC at the level of the bottom of the beams then lay the 'slips' on this and lay the block on top of these with a mortar bed in between.