What type of lintel do i need.

[amazondean]

Hi. I am having my rear dining room extended soon and wanted to know what type of lintel to use when the outside load bearing walls are opened up. The opening will be 3 metres so i am assuming i would need a 3.3 metre lintel. Could a catnic lintel be used or do i need an RSJ.

The house is a 1930's 3 bed semi with rosemary tiles to the roof.

 

[^woody^]

You can use any lintel you like which is long enough to span the opening and suitable for the thickness/type of wall.

Catnic is a brand name, and their boot lintels are a pain to insert retrospectively. Look for one which is like an upside down T - such as made by IG

 

[noseall]

Regardless of whether you use a catnic or a u' beam, you will still need to show calc's to building control.

It may work out cheaper and less hassle to employ an s.e. to spec'-up a pair of steel beams and provide the calc's.

There is no set precedent, as all houses have different loading points throughout the building. That is not to say you couldn't fit an over sized steel beam, knowing it would be more than man enough, but it is no good without calc's.

 

[amazondean]

ok. How do i go about getting calculations. I have got no idea about this. Do i look in yellow pages or something. I presume someone comes round and does the calculation. What sort of price do they charge for this?

 

[^woody^]

You wont need any calculations if a standard lintel is used.

 

[amazondean]

This is getting interesting. I have been quoted around £150 for a catnic lintel 3.3 metres long. They seem to be a nice weight for two people to lift in. If i don't need calculations why would anyone bother anyway or is this incase you are using a made up beem.

If i can get away without the hassle of calculations that would be fine by me. I have had a few builders round to look at the job. One said i needed calculations but none of the others have. I am quite happy to pay £150 for the catnic and get on with it. I asked the building supplier about the lintles and he said that the size i was looking at is what is used for what i want so i am a bit confused about the idea of calculations.

 

[^woody^]

The manufacturers publish loading tables for their products. You tell the council what lintel it is, and they will already have the details to know that it is satisfactory for a given use.

It should be the same with steel beams, as the council should know how much load a section can take, but in most cases they tend to ask for calculations. But some councils will accept steel beams up to a certain span (3m) without calculations.

 

[noseall]

But some councils will accept steel beams up to a certain span (3m) without calculations.

1.8m 'round here.

 

[^woody^]

LOL - is it worth it?

 

[alittlerespect]

On the assumption that you have applied for Building Control Approval, Building Control are unlikely to sign off/certificate the work without having sight of the beam design calculations to ensure so far as is reasonably practicable that the beams that are specified are capable of withstanding the imposed loadings (live and dead).

Steel merchants should be able to give you the size requirements over the phone, but you will still need to provide the design calculations. I mention steel merchants as I would use 2 'I' section beams (rsj's) for the job - assuming you have a cavity wall, if you have a solid wall then I would use a single pre-stressed concrete lintel, some may suggest 2 narrow concrete lintels, but the load bearing characterstics are not equal - again design calcs would be needed.

If you don't go for Building Control Approval you could create problems for yourself if you ever consider moving home.

Regards

 

[^woody^]

I would use 2 'I' section beams (rsj's) for the job - .... , if you have a solid wall then I would use a single pre-stressed concrete lintel,.

And then how would you cover the beam on the external face?

And I am sure a big lump of concrete would look nice when sitting on the patio.

Both of these would look a right mess - not to mention lifting a 3.3m concrete lintel!

 

[mater]

i would say that on a 3m opening you would need a 3.6, as a 150 end bearing is not enough on a 3m span. go for catnic style then no calcs needed as they are done by the manufacturer

 

[jono_h]

My experience from the extension that I've just done was that the BCO wasn't bothered about calcs for standard box and cavity lintels (Catnic etc) over doorways and windows.

He did want calcs for the steel RSJ's that were supporting the second storey brickwork, and the roof timbers.

 

[mointainwalker]

Peter

If it is as it appears - i.e. you are trying to generate some business for yourself - you will not get far by trying to sell to someone who had a need in 2009.

Read the dates when you search, but better still don't try to hang your sales-spiel on everything where someone says they need calcs.

 

[mointainwalker]

Peter

If it is as it appears - i.e. you are trying to generate some business for yourself - you will not get far by trying to sell to someone who had a need in 2009.

Read the dates when you search, but better still don't try to hang your sales-spiel on everything where someone says they need calcs.