Lintel position for wide opes

grassynoel

1st floor concrete slab provider recommended double concrete lintels for any opes up to 1.8m to carry floor (150mm & 75mm screed), architect said RSJ 203x102x23Kg for anything up to 3m on inner leaf to carry the 1st floor. Got the list of RSJ's needed from the block layer and went and got the RSJ's and got timber bolted on to carry plasterboard after for all the >1.8m spans.

Question finally is, I noticed the blocklayer has put concrete lintels directly spanning the top of the opes that are to carry the RSJ's, then a course of 4" block on the inner leaf and then the RSJ top of this course of blocks. I would have thought that the RSJ would have gone on first to span the ope and continue the blocks on the inner leaf upwards to the top of the ground floor ceiling?

I also had to get a steel lintel with integrated insulation (3.81m) for a large window and I noticed this is spanning the top of the wide window and then 2 concrete lintels on top of each other, then blockwork.

Are the RSJ's on top of the concrete lintels doing their job in this position, or is this overkill or is this normal? Advice/experience appreciated, thanks.

mickdw

The concrete lintels are composite lintels i.e. they require an amount of blockwork overhead in order to gain the strength.
These type of lintels should never be doubled up in an attemp to gain extra strengh. This is not how they are designed. Standard procedure would be to place your rsj over window ope and continue blockwork over

sinnerboy

Get your certifying architect or engineer to make an immediate inspection

Your blocklayers sound incompetent

Watch out for -

bent twisted wall ties , congested in mortar snots
cavity insulation boards with large gaps at butt joints , and leaning forward into air space of cavity
missing - dpc's and / or in parts , insulation - Particularly around lintols jambs and cills
pay particular attention at the base of you wall . mortar droppings can gather nicely here and by pass your dpc . Open up 2 or 3 blocks blocks at this level about 4 blocks apart and have a look

this is what I fear you can expect from such "tradesmen"

grassynoel

Sheeeite! was thinking the RSJ's should be going directly on top of the ope, whats the point otherwise. Paid €9/foot for steel, primed it plus got the timber bolted on Very disapointed with blocklayer, he is actually very good and has a good rep locally. His work to this level has been good, insulation closely butted, clean ties, dpc correct, a bit of mortar down the bottom alright though I notice.

Will be on to the architect 1st thing monday morning to confirm incorrect positions and then he'll be pulling down a couple of courses to get it right.

Although, architect and hollowcore provider said to double up on concrete lintels for any ope up to 6 foot!

mickdw

It would not be the end of the world if say he has a concrete lintel and some blockwork then at a higher level the rsj spanning the complete ope. At least the rsj is then taking the load from above and the conc lintel is only supporting the construction below the rsj. 2.5m (Depending on loadings) is generally the max ope for a 65mm prestressed lintel and there are no design tables for wider opes or for using two lintels directly on top of each other. It seems to be gathering some acceptance this idea of doubling up the lintels although I have no idea why or who approves this. I have seen numerous cases of cracking between the two lintels although this is mostly in cases where they were used in opes that were over 2.5m

Anyone know of any design information in relation to doubling up of prestressed lintels?

mickdw

On a seperate issue, Does your house have any areas where stepped cavity trays will be required? This is critical. A dodgy blocklayer will not even know what they are, never mind know how to build them in.

grassynoel

Tried to get pics of the work to show ye but i failed the technology. Just back in from site and had a closer look. He has put 1 ps lintel on either side of the steel lintel and continued the blockwork for the wide window, which I think is ok?

For 2 patio doors (wide opes) he has first spanned with ONE ps lintel then continued the wall on the inner leaf with a 4" block on edge, followed by a 6" soap followed by the RSJ to the level where the 1st floor slabs are to rest (and will be bearing on this wall). The RSJ is spanning the ope completely although at a height of the courses listed above, above the top of the ope, so this might still work? I wouldnt mind the excessive ps lintels underneath the RSJ's as long as structural integrity was not affected.

Noticed he has put 2 ps lintels on top of each other on some standard windows, is this probably to get his courses level again with as little work as needed.

Have a porch on the front of the 1.5 storey house with the apex of the roof lower than the eaves on the main house above that will need stepped cavity tray I think (saw something in the HB manual on this, must read up and talk to him) looks complicated enough for Irish site conditions though unless you stand over lads.