Wall plate sitting on lintel

[Bonner]

Is this a standard construction detail? The builder is saying it is necessary to put masonry on the lintel before the wall plate but that will raise the eaves and ridge height. If masonry is not needed should he just bed the wall plate on the lintel with mortar?

[tonyshouse]

Tray lintels are designed to carry blocks, the plate should be as thin as possible to save undercut that weakens rafter.

 

I would prefer to see decent angle iron, all the lintel does is introduce thermal bridging when the outside tray is doing nothing  

[Bonner]

Thanks @tonyshouse, apologies I should have said the lintels are already in. Take your point about thermal bridging so will see if they can replaced. If not, is it acceptable for the wall plate to sit directly on a lintel without a course of masonry?

[Dave Jones]

no problem at all sitting wall plate on a lintel. It's less weight on it if you think about it.

[markc]

No problem unless it's a composite lintel as they are designed and manufactured to work in conjunction with the stated number of masonry courses above. Plain tensioned concrete are fine.

[Bonner]

2 hours ago, Dave Jones said:

no problem at all sitting wall plate on a lintel. It's less weight on it if you think about it.

 

That certainly makes sense but it depends how that weight is distributed. The architect has shown quite a thick wall plate, presumably to distribute the load ...

[Bonner]

2 hours ago, markc said:

No problem unless it's a composite lintel as they are designed and manufactured to work in conjunction with the stated number of masonry courses above. Plain tensioned concrete are fine.

 

Not sure what you mean by a composite lintel, these are standard steel Catnic cavity wall lintels. I looked on the Catnic website but couldn’t see any specific guidance but IG site mentions minimum 150mm of masonry. 

[markc]

34 minutes ago, Bonner said:

 

Not sure what you mean by a composite lintel, these are standard steel Catnic cavity wall lintels. I looked on the Catnic website but couldn’t see any specific guidance but IG site mentions minimum 150mm of masonry. 

Some lintels only attain the given strength when they have the recommended masonary on them. Single course pre stressed concrete lintels are usually composite and so are some steel versions.

not a problem using without the marinara as ling as the loads above are relatively low compared to the maximum given

[Temp]

Have you got a structural ridge beam? What stops rafter spread pushing the lintel off the wall?

[PeterW]

Builder is correct unless it’s a box lintel. Eaves lintels have a shorter outer flange but all require blockwork on the inside. You could get BCO to agree to use a 140mm concrete lintel on the inner flange but it would depend on the span if you could get one long enough. 

[Bonner]

48 minutes ago, Temp said:

Have you got a structural ridge beam? What stops rafter spread pushing the lintel off the wall?

 

Yes, big glulam ridge beam and cut rafters, calcs done by the truss supplier so should not see significant horizontal load.

[Bonner]

20 minutes ago, PeterW said:

Builder is correct unless it’s a box lintel. Eaves lintels have a shorter outer flange but all require blockwork on the inside. You could get BCO to agree to use a 140mm concrete lintel on the inner flange but it would depend on the span if you could get one long enough. 

 

Cheers Peter, we have agreed to check with BCO and the SE if necessary. Slightly surprised this detail was drawn by the architect and approved by BC but I am sure we will find a solution.

[epsilonGreedy]

6 hours ago, Dave Jones said:

no problem at all sitting wall plate on a lintel. It's less weight on it if you think about it.

 

 

The issue of concern is point loads and as another poster mentioned possible local twisting action. This might be a regional thing but down here in England brickies consider two courses of masonry a minimum requirement.

[tonyshouse]

Likely so do the lintel manufacturers. 
 

if it were mine I would replace them with angle irons - building regs or the inspector might ask for calcs, these could be difficult/impossible and ugly trying to replace a lintel after the roof has been built. 

[Bonner]

Thanks everyone, I will share the outcome of discussions with BCO/SE when we have agreed a solution. 

[Bonner]

Well I think we have a solution for that issue, SE has agreed concrete lintel over the  That is for the single storey living room, However it gets worse on the main roof ...

This is the eaves detail, similar to the single storey but trusses here with raised tie (3.3m first floor ceilings)

 

 

That is the drawing sent to the truss manufacturer and this is what they made ...

 

 

No prizes for spotting the difference - chord depth 365mm compared to 210mm on the drawing, also 200mm wide foot will have to sit over the lintel not behind it. Consequence would be 6-7 courses of brick over the windows rather than one course shown.

 

Having spoken to all parties involved on Friday, what happened is :

Architect designed something that is difficult / impossible to build, but they argue their drawings are ‘representative’ and must be checked by truss manufacturer or SE.

Truss manufacturer are admitting they had the drawings but cannot make anything to fit and told the builder this.

Builder ordered them without coming back to me or architect

 

So what happens now ...

Truss manufacturers are looking how these can be modified to at least get them lower (3 courses of bricks over the window head would be acceptable, 6-7 course is a major design change)

Architect is looking for construction details of similar designs they have done in the past.

Builder is busy avoiding any responsibility and blaming everyone else 

 

I am prepared to compromise (so far) because it seems the original concept was just that, would have to be modified at some point. Also, the build is dragging on far to long and we don’t want any further delays. It would have been so much better if this was recognised earlier, we could have adapted the design without much drama.

 

Thanks for reading this sorry story and let it be a lesson for others as it has been for me

 

Any ideas for a solution would be highly welcome!

[Dave Jones]

why have you got a lintel so high up in the first place or is the roof just low ?

[Bonner]

3 hours ago, Dave Jones said:

why have you got a lintel so high up in the first place or is the roof just low ?

 

The design had tall windows with the roof sitting low over them, a barn like concept. Since we cannot raise the eaves, reducing the window height is the most likely compromise. I am not worried about the window size but it will change the look quite significantly.

As mentioned, if I knew about this earlier I would have gone back to the drawing board with the design.

[Dave Jones]

ok i understand, and can see why the truss company have made them massive to get over it.  The truss load is taken by the inner skin so you will need to notch it over the cavity upstand on the lintel. If you are using building control then you will need paperwork from the truss supplier saying its ok to butcher their truss otherwise their structural calcs which your BC will need to give you a completion cert will be invalid.

 

Only ever met 1 Architect who had any sort of clue about how to build anything. Most of them cant even design a window or door to work brick.

 

 

[Brickie]

What width is the window shown? 
Would it be feasible to sister up the trusses either side,have the head of the windos as an upstand (kind of like a dormer) and trim across to suit?

[Bonner]

1 hour ago, Dave Jones said:

If you are using building control then you will need paperwork from the truss supplier saying its ok to butcher their truss otherwise their structural calcs which your BC will need to give you a completion cert will be invalid.

 

Completely agree, nothing will be changed without calcs from the truss manufacturer 

[Bonner]

38 minutes ago, Brickie said:

What width is the window shown? 
Would it be feasible to sister up the trusses either side,have the head of the windos as an upstand (kind of like a dormer) and trim across to suit?

 

All the windows are 1250mm wide except a 3m wide double height opening which could be treated differently.

That might work! When you mention an upstand or dormer do you mean lowered trusses (and ceiling) either side of the windows? We want to avoid changing the roofline if possible...

[Brickie]

A bit like this? 
Ive no idea on the engineering/design practicalities but it seems you’re having headaches solving the lintol/depth issues & at the same time losing height & light from your window. 

[Brickie]

5 hours ago, Bonner said:

All the windows are 1250mm wide

How many are going to have the same issue?

[Bonner]

3 hours ago, Brickie said:

How many are going to have the same issue?

 

7 windows, 4 at the front and 3 at the back. Unfortunately only one pair line up front to back so doubling up the trusses either side will be difficult.