Internal Garage Door Lintel Choices

[deadfire19]

I'd like to install an internal door to an internal garage.

The wall is an external 215mm wall and it is load bearing. I'm wondering what lintel to install above it. The LABC lady advised against a prestressed lintel since there is already weight on the solid brick wall from above. She mentioned that the lintel should be 100mm+.

However I can't find any non-prestressed lintels in the building merchants. This is the best I could find: https://www.builderdepot.co.uk/140mm-x-215mm-prestressed-concrete-lintel-textured-1200mm

I'm considering putting in a steel lintel for this reason. https://www.selcobw.com/l9-solid-wall-external-lintel

I will double check any decisions with LABC of course, but I'd like the advice of someone who's done this before.

Ideally the lintel should be max 100mm tall to fit a standard height door.

Ignoring cost, which lintel is better for my situation?

 

[^woody^]

Unless you have a massive point load directly on or immediately above the proposed lintel, then 65mm concrete lintel will be fine.

Your inspectors' comments regarding the weight above will apply to any lintel.

 

[deadfire19]

Unless you have a massive point load directly on or immediately above the proposed lintel, then 65mm concrete lintel will be fine.

Your inspectors' comments regarding the weight above will apply to any lintel.

The proposed lintel will start at the edge of the steel in the concrete cieling, just under where the ducting goes into the wall.

There is a concrete garage cieling it's supporting and a single brick wall upstairs. There is a huge 400x400mm pillar that the steel in the concrete cieling is sitting on behind that wall.

A similar opening done on the opposite wall of the garage has a 140mm lintel, although it's unclear if thats prestressed or just reinforced concreted.

 

[^woody^]

There is nothing unusual with that loading situation, so a 65mm concrete lintel will be fine. You have an inexperienced inspector there.

That 140mm concrete lintel is that depth because that's how they made the formwork to cast the lintel in the past, they never cast 3" lintels, always 6" or 9" on a whim.

Don't stress about prestressed. It's really just a colloquialism for any concrete lintel, and pre-stressing is only required in specific loading situations and none of which normally apply to domestic work. Just get the cheapest one off the shelf at the merchant, it will be reinforced.

 

[deadfire19]

There is nothing unusual with that loading situation, so a 65mm concrete lintel will be fine. You have an inexperienced inspector there.

That 140mm concrete lintel is that depth because that's how they made the formwork to cast the lintel in the past, they never cast 3" lintels, always 6" or 9" on a whim.

Don't stress about prestressed. It's really just a colloquialism for any concrete lintel, and pre-stressing is only required in specific loading situations and none of which normally apply to domestic work. Just get the cheapest one off the shelf at the merchant, it will be reinforced.

Thank you for the response, this is very helpful.

Is it worth getting a 100mm thick lintel for any reason, am I likely to regret going with a 65mm one? (I've found a 100mm*215mm, I could order online).

I can fit a 100mm lintel with no problems.

As a follow-up question, how many acrows + strong boys would you install to hold up that 1200mm span during lintel installation?

(I was going to go with two acroes to push up on the garage concrete ceiling, to reduce the load on the wall slightly, and two strongboys + acrows to hold up the span.) It's my first time doing this and I've heard more is better.

 

[^woody^]

A 100mm lintel will do, but does that make it more difficult to fit if it does not align with the brick courses. Bear in mind that size lintel will be very heavy and awkward to lift and manoeuvre.

One prop will do on that side, with a piece of 50mm thick timber x 500mm or so long at the top and bottom.

Likewise if the other side of the wall is the same.

 

[Peter500]

A structural engineer spec'ed a 140mm concrete lintel for my new garage. The span is 900mm and there will be 300mm of blocks above plus a flat roof. It does seem a bit excessive IMO, but the SE probably/hopefully knows what he's doing