Lintel for new window heads in 330mm thick walls

[jayc89]

We're looking to install window heads to our existing openings (they were taken out many years ago for some reason....)

Some walls are 215mm thick so standard solid-wall lintels will work there, something like this - https://condell-ltd.com/lintels/solid-wall-lintels/catnic-cn71a-lintel-2250mm

 

However others are around 330mm thick and I'm struggling to find a single lintel to do the trick. What's the best approach, I can use an L-shaped lintel to the external face (like this - https://condell-ltd.com/lintels/single-leaf-lintels/catnic-ang-single-leaf-wall-lintel-2700mm) 2400mm), but I don't know what to put behind it towards the internal face, a 215mm prestressed concrete lintel, or is there a better solution?

[Jenki]

5 hours ago, jayc89 said:

However others are around 330mm thick and I'm struggling to find a single lintel to do the trick. What's the best approach, I can use an L-shaped lintel to the external face (like this - https://condell-ltd.com/lintels/single-leaf-lintels/catnic-ang-single-leaf-wall-lintel-2700mm) 2400mm), but I don't know what to put behind it towards the internal face, a 215mm prestressed concrete lintel, or is there a better solution?

You could get an RSJ and stainless plate welded for the wider one. 

[bassanclan]

You could buy wet cast heads which are structural and don't need a lintel (they are the lintel) and then a concrete lintel for the inner leaf

[jayc89]

12 hours ago, Jenki said:

You could get an RSJ and stainless plate welded for the wider one. 

 

I saw that recommended somewhere else, with the caveat that it would need to be designed by a SE, is that correct?

 

3 hours ago, bassanclan said:

You could buy wet cast heads which are structural and don't need a lintel (they are the lintel) and then a concrete lintel for the inner leaf

 

They sound expensive

I spoke with Catnic who are recommending a standard 215mm solid wall lintel followed by a box lintel on the internal face to make up the additional 100mm. 

[severnside]

We had similar situation in couple of walls one 300mm and another about 400mm with stone face. For 300mm wall we had RSJ with 8mm steel plate welded on underside.

For 400mm we tried L shaped catnic Lintel but when we put stones on it (200mm) it bent slightly forward so we had to remove it. Now we are using 200 x 200 x 16 EA for front stone face wall.

[jayc89]

4 minutes ago, severnside said:

We had similar situation in couple of walls one 300mm and another about 400mm with stone face. For 300mm wall we had RSJ with 8mm steel plate welded on underside.

For 400mm we tried L shaped catnic Lintel but when we put stones on it (200mm) it bent slightly forward so we had to remove it. Now we are using 200 x 200 x 16 EA for front stone face wall.

 

Did that need designing by a SE or did you JFDI? 

[severnside]

Both of them suggested by SE but it took him 2 minutes to answer as it's very standard stuff. The RSJ with steel plate for a different reason as we had another RSJ linking into it otherwise it could have been a simpler solution. 

[jayc89]

I guess the other downside to lintels/RSJs over structural heads is you'll be able to see the bottom of the lintel over the window, won't you?

[George]

Painted black it's not noticeable - stone/brick can't float so you need something there.

 

Catnic has the right idea - multiple standard lintels to make up the width of the wall.

[bassanclan]

3 hours ago, jayc89 said:

I guess the other downside to lintels/RSJs over structural heads is you'll be able to see the bottom of the lintel over the window, won't you?

Yes that is the problem with dry cast heads. Wet cast is probably 40% more last time I bought some, but then you have no lintel to buy

[jayc89]

£10k for stone window heads. £1.2k for pre-cast ones. 10x more expensive  

[jayc89]

Builder is recommended a Solid Wall Lintel to the external face and then an L-angle lintel to the internal face. Whereas Catnic are recommending a Solid Wall Lintel to the external face and a box lintel to the internal face. 

 

The difference is the loading figures to the internal face;

 

L-angle supports up to 19kN whereas the box lintel supports up to 47kN. What's typically spec'd on a 1.5 brick thick wall? Are Catnic just being over cautious, or is their valid reason to go for such a stronger lintel?

 

Standard 9" clay brick wall. 

[Iceverge]

 

 

Can you not buy precast lintels off the shelf in the UK? 

 

They're ubiquitous and really cheap here. One for the internal leaf and one for the external.

 

Anything that needs to take more load gets an RSJ. 

 

 

 

 

 

[jayc89]

47 minutes ago, Iceverge said:

 

 

Can you not buy precast lintels off the shelf in the UK? 

 

They're ubiquitous and really cheap here. One for the internal leaf and one for the external.

 

Anything that needs to take more load gets an RSJ. 

 

 

 

 

 

 

That's ludicrously cheap. They're at least double, from what I can see, here. And not much more than an L-angled Catnic.

[bassanclan]

Real stone is always going to be pricey. Have you got a quote for wet cast?

[Iceverge]

It's just some rebar and concrete. I can't see where the cost goes.

 

How much are catnics for interest?  

 

You could pour your own concrete ones in situ. Use an appropriate dye match local stone.  Should be a 2 minute job for the the engineer to calculate. 

 

[jayc89]

20 minutes ago, bassanclan said:

Real stone is always going to be pricey. Have you got a quote for wet cast?

 

£5k but still non-structural. The company want an engineer's report prior to quoting anything structural. Structural won't work for us anyway as we're wanting splayed heads, where the bottom is the same width as the window, however the companies I've spoke with have said even splayed heads need a 150mm bearing at either side, which would just look odd. 

 

So we're looking at lintels + dry cast, I think. 

[jayc89]

6 minutes ago, Iceverge said:

It's just some rebar and concrete. I can't see where the cost goes.

 

How much are catnics for interest?  

 

You could pour your own concrete ones in situ. Use an appropriate dye match local stone.  Should be a 2 minute job for the the engineer to calculate. 

 

 

£30 is the cheapest I've been quoted for the L-angled lintels.