We often assume that the load span tables featured in our lintel guide are easy to understand, which for those with knowledge; probably are. However, for anyone starting out in the industry, getting to grips with interpreting the load spans for prestressed concrete lintels and steel lintels is not always straight forward.

This post examines the load span tables featured for both concrete and steel lintels and will demonstrate how you should interpret the values within them. This post is not going to help you with the calculations to arrive at what loads you need the lintel to bear – that is for another blog post.

#### Lintels are independently tested

The first point we need to make is that the load span tables in this post are based on our own products. These products are CE marked, and in order to obtain this accreditation, lintels are subject to the most stringent tests under the Construction Products Regulation (CPR). This means they are independently tested. The values in our own tables have been independently verified by a third party.

#### Lintel load span definitions

We will look at the load span tables for two steel lintel products at either end of the ‘strength’ spectrum. Initially we will make sure we know what values are included in the table.

**Standard Lengths** – This is pretty self-explanatory, and simply means the length of the lintel. As standard our steel lintels increase in length by 150mm, the two values represent the length of the lintel that the values in that column relate to. If it is 600 | 1200 it means the load span details can be applied to any lintel between 600mm and 1200mm.

**Nominal height** – The height of the lintel in mm.

**Weights** – The weight of the lintel in kg per metre.

**SWL** – This means Safe Working Load, but can also be referred to as Serviceable Working Load. This value is the load in kiloNewtons (kN) and simply means the load that this particular lintel can *safely* bear.

**RM** – This means Resistance Moment. RM is quite difficult to explain, and quite frankly is best described by a qualified engineer. In very simple layperson terms it is the force (as measured by kiloNewtons metre; kNm) at which point the lintel breaks. You can find out more about resistance moment here.

###### Got a question?

If you have a question, then you can email us directly. At the bottom of this page is a quick ‘ask a question’ section, just fill out your name and email (it won’t be shared) and drop your question in the box… easy.#### Understanding lintel load ratios

The SWL values in our load span tables are often subject to load ratios. These ratios represent the ratio of load that the lintel can bear as inner leaf to outer leaf. The ratios are different for the different applications.

- 1:1 – Lintels supporting masonry only
- 3:1 – Lintels supporting masonry and timber floors
- 5:1 – Lintels supporting concrete floors
- 19:1 – Lintels for eaves applications

How these ratios are applied will be demonstrated in the examples below.

#### Steel lintel load span tables

This first load span table is for a standard 50mm cavity lintel. The second table is for a 50mm composite extra heavy duty (CXHD) lintel.

SL50 | Standard Lengths | 600 1200 | 1350 1500 | 1650 1800 | 1950 2100 | 2250 2400 | 2550 3000 | 3150 3900 | 4050 4200 | 4350 4800 |
---|---|---|---|---|---|---|---|---|---|---|

Nominal Height | (mm) | 95 | 113 | 134 | 140 | 153 | 190 | 190 | 225 | 225 |

Weights | (kg/m) | 6.2 | 6.8 | 7.4 | 7.6 | 8.0 | 9.2 | 13.8 | 15.5 | 17.8 |

SWL 1:1 | 3:1 | (kN) | 16 | 17 | 22 | 23 | 24 | 28 | 28 | 28 | 28 |

SWL 19:1 | (kN) | 12 | 13 | 17 | 18 | 19 | 22 | 22 | 22 | 22 |

RM | (kNm) | 2.2 | 2.9 | 4.5 | 5.6 | 6.8 | 10.0 | 13.3 | 16.2 | 16.2 |

SL50 CXHD 225 | Standard Lengths | 600 1800 | 1950 3000 | 3150 3900 | 4050 4500 | 4650 4800 | 4950 5100 |
---|---|---|---|---|---|---|---|

Nominal Height | (mm) | 236 | 236 | 236 | 236 | 236 | 236 |

Weights | (kg/m) | 19.0 | 19.0 | 19.0 | 19.0 | 19.0 | 19.0 |

SWL 1:1 | 3:1 | (kN) | 89 | 71 | 55 | 42 | 37 | 32 |

SWL 19:1 | (kN) | 75 | 60 | 46 | 40 | 35 | 30 |

RM | (kNm) | 21.5 | 21.5 | 21.5 | 20.5 | 20.5 | 20.5 |

Let’s assume you need a 900mm lintel, you would look at the details of the first column of each of the two tables.

A 900mm SL50 has a height of 95mm, and weighs 6.2kg per metre.

Looking at SWL figures you can see that if your floor load is a 1:1 ratio (so the same weight is applied on both the inner leaf and outer leaf, then this SL50 at 900mm can take a load of 8kN on each leaf.

If you needed your lintel for an eaves application, then you would use the 19:1 ratio, which means this lintel would take an inner leaf load of 11.4 kN and an outer leaf load of 0.6 kN (rounding up). In reality; this is probably not the best lintel for the job.

Looking at the CXHD lintel, you can see the SWL for 19:1 is 75 which equates to approximately 71kN on the inner leaf and 4kN on the outer leaf. This level is used for extreme loads.

Like I said at the start of the post, the calculations for working out what your load will be is for another post, but once you know this (and the other factors affecting lintel selection) then you will be able to quickly see which sort of lintel you need to use for the job.

#### Prestressed concrete load span tables

The load span tables for prestressed concrete lintels are very similar to the steel lintel tables with the exception of two values.

UDL means uniformly distributed load which is measured in kiloNewtons per metre (kN/m). The principle is the same however; the higher the value, the better the load bearing capabilities on the lintel.

###### kNm or kN/m?

Note: Do not confuse kNm with kN/m. kNm is a force measurement kiloNewtons times metres, kN/m is kiloNewtons per metre (or divided by metre).Clear span is very simply the length of the opening. If you have a clear span of 1200mm, you will need a 1500mm length lintel to accommodate the required 150mm span on each side of the opening.

The R15 is a popular concrete product; here you can see the load table values up to a length of 1800mm.

R15 140 x 100 | Standard Lengths | 1050 | 1200 | 1350 | 1500 | 1650 | 1800 |
---|---|---|---|---|---|---|---|

Clear Span | (mm) | 750 | 900 | 1050 | 1200 | 1350 | 1500 |

Weights | (kg/m) | 33.0 | 33.0 | 33.0 | 33.0 | 33.0 | 33.0 |

UDL | (kN/m) | 35.9* | 26.3 | 19.3 | 14.8 | 11.8 | 9.5 |

RM | (kNm) | 3.0 | 3.0 | 3.0 | 3.0 | 3.0 | 3.0 |

*This UDL value is restricted by shear, which means the UDL would be higher were it not for the shear force which would snap the lintel first.

Hopefully, this will have provided a simple introduction to lintel load spans and what the values in the load span tables mean. However, if you have any questions about lintel selection, load span calculations or lintel specification, our technical team are more than happy to assist. Contact them at technical@stressline.net.

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## Comments 11

Am I missing something? You state, “span of 1200mm, you will need a 1800mm length lintel to accommodate the required 150mm span on each side of the opening”, yet 1200 + 150 + 150 = 1500, not 1800. Could you please explain? Many thanks.

Author

Hi John

Thanks for bringing this to my attention. No, you’re not missing anything; I am missing my maths book, or perhaps it was a typo, either way you are correct. I will amend it now. Thanks ever so much for pointing it out.

I am installing a 48″ wide casement window in my basement. It is a block wall. What size angle iron do I need to use to support a single story wood frame home. Windows will be installed on the bearing block walls. I want to use angle iron so do I need to install it on the inside and the outside or can I use, EXAMPLE 6″X 2″ X ?. The block wall is not filled with cement so what length do I need in order to transfer the load properly? Thanks for your help Paul

Author

Hi Paul,

Thank you for raising this query. I have emailed our technical department who will be in a better position to assist you. Thank you.

Andrew

Hi , is the bearing still 150 each side for a span of 4200 or does it go up to 200 ?

Thanks.

Author

Hi Paul

thanks for the question. I don’t believe it is in the standards, but I will double check and reply again. Thanks, Andrew

What is the strength of concrete used in prestressed lintels.

Can you say what the permissible shear stress is in the lintel.

I am considering a point load near the support.

Author

Hi David

Thanks for the question. Our prestressed concrete lintels are designed with a concrete strength of 50 N/mm2. I hope this helps but please feel free to download our lintel guide which has more information or contact our technical team. Thanks again, Andrew

Author

Sorry David,

I didn’t answer your question about shear stress. It would depend on other factors. If you can email me directly on andrew (dot) sanderson (at) stressline (dot) net with as much detail as possible, we will endeavour to help and advise as best as we can. Thank you,

Andrew

“Looking at SWL figures you can see that if your floor load is a 1:1 ratio (so the same weight is applied on both the inner leaf and outer leaf, then this SL50 at 900mm can take a load of 16kN on each leaf.”

I think this should be 8KN on each leaf? Bacause the safe working load, SWL is exceeded if this is true, as the lintel is then taking 32KN from both leaf! instead of the 16KN Total!

Author

Hi there

Yes, you’re right! Thanks. Not sure how this made it past my stringent proof-reading protocols but hey. I have now changed it, and thank you for bringing this to my attention.

All the best,

Andrew.