GEO-PAR Posted October 20 Share Posted October 20 (edited) I need to order my stone cills and lintels asap but getting cold feet on how I planned to do it. Interested to know what others think - Whether I'm being a little mad or if it will be okay? My intention was to have a natural limestone lintel self supporting. I only wanted it to bear onto the stone walls either side by 50mm (for visual reasons) but now questioning if that's enough. I'll then stick a Catnik CN71A (or similar) above it with a 10mm gap for deflection (so the steel doesn't crack the stone if it deflects). This steel will have your typical 150 bearing each side. I want to keep this above the limestone lintel so when you look up at the window, you don't see any steelwork. Edited October 20 by GEO-PAR Link to comment Share on other sites More sharing options...
nod Posted October 20 Share Posted October 20 Why don’t you just sit the stone lintel in a catnic 1 Link to comment Share on other sites More sharing options...
scottishjohn Posted October 20 Share Posted October 20 If you do not use a catnic with inset limestone then a lintel will need to be at least 150mm into wall each side and thick you will need to be very specific on size with stone supplier if you want to set a one piece one in wioth planty of clearance to fit it in as the steek defllects does not need to be thick as its just for show Is this a new build or extension on exsisting stone building Link to comment Share on other sites More sharing options...
scottishjohn Posted October 20 Share Posted October 20 3 hours ago, GEO-PAR said: 10mm gap for deflection 19mm would be normal gap for bedding it --so maybe a bit more clearance you need to knpw the deflection to work out how big gap for bedding you will need,so it looks right Link to comment Share on other sites More sharing options...
GEO-PAR Posted October 20 Author Share Posted October 20 3 hours ago, nod said: Why don’t you just sit the stone lintel in a catnic Because then you'll see the underside of the steel when you look up below the window Link to comment Share on other sites More sharing options...
GEO-PAR Posted October 20 Author Share Posted October 20 3 hours ago, scottishjohn said: If you do not use a catnic with inset limestone then a lintel will need to be at least 150mm into wall each side and thick you will need to be very specific on size with stone supplier if you want to set a one piece one in wioth planty of clearance to fit it in as the steek defllects does not need to be thick as its just for show Is this a new build or extension on exsisting stone building I did wonder this. I've seen it don't before where the edge of stone head aligns with the opening reveal (I.e so no bearing at all). No idea how you'd do this. Link to comment Share on other sites More sharing options...
GEO-PAR Posted October 20 Author Share Posted October 20 3 hours ago, scottishjohn said: 19mm would be normal gap for bedding it --so maybe a bit more clearance you need to knpw the deflection to work out how big gap for bedding you will need,so it looks right Okay cheers Link to comment Share on other sites More sharing options...
nod Posted October 20 Share Posted October 20 55 minutes ago, GEO-PAR said: Because then you'll see the underside of the steel when you look up below the Sounds an expensive way to go about it Link to comment Share on other sites More sharing options...
nod Posted October 20 Share Posted October 20 Just now, nod said: 57 minutes ago, GEO-PAR said: Because then you'll see the underside of the steel when you look up below the Sounds an expensive way to go about it I would push your frames forward to hide the lintels It would cut your exterior reveals down to 50 mil Link to comment Share on other sites More sharing options...
GEO-PAR Posted October 20 Author Share Posted October 20 44 minutes ago, nod said: Yeah I appreciate it will make it a whole lot cheaper but it's not a house I'm intending to flip, so want to get it right. But equally think what I've drawn may cause issues. I'm wondering how they managed to achieve this - Super deep reveals with no exposed lintels. My guess is that they cast the stones into some kind of concrete lintel. Link to comment Share on other sites More sharing options...
Mr Punter Posted October 20 Share Posted October 20 With just 50mm end bearing I think the stone lintel will look wrong. Go with 150mm minimum. Link to comment Share on other sites More sharing options...
GEO-PAR Posted October 20 Author Share Posted October 20 6 minutes ago, Mr Punter said: With just 50mm end bearing I think the stone lintel will look wrong. Go with 150mm minimum. Yeah I think I'm going to boost it up to at least 100 if not 150 like you suggest. I found this picture where the bearing looks about 50mm, but it's granite so being a harder stone, I guess this makes it possible Link to comment Share on other sites More sharing options...
scottishjohn Posted October 20 Share Posted October 20 8 minutes ago, GEO-PAR said: Yeah I think I'm going to boost it up to at least 100 if not 150 like you suggest. I found this picture where the bearing looks about 50mm, but it's granite so being a harder stone, I guess this makes it possible still wrong , thelintel will be ok buy could crush those small bits under it Link to comment Share on other sites More sharing options...
Gus Potter Posted October 22 Share Posted October 22 On 20/10/2024 at 12:38, GEO-PAR said: I need to order my stone cills and lintels asap but getting cold feet on how I planned to do it. Interested to know what others think @GEO-PAR I do like what you're trying to achieve, very elegant Architecturally. On 20/10/2024 at 15:54, scottishjohn said: you need to knpw the deflection to work out how big gap for bedding you will need,so it looks right Deflection is a key.. will come to that in a bit. I think you will have trouble with that at the clear span of some 1800mm. The way it is detailed is potentially risky in terms of failure of the stone lintel and bits falling on folk. Here are a few comments (with my SE hat on) on the structural design of something like this at this span. Firstly though for all stone lintels can work well if the span is short (image by @scottishjohn) and you have masonry above that is bonded to the top of the stone (no dpc / cavity tray as this acts as a slip plane) the composite action (stone lintel and masonry working together) form an arch thus the actual load on the stone lintel is small. For a piece of stone spanning ~1.8m say with a shallow depth of 150mm the primary design force is going to be a bending force, unless you have a huge uninterrupted wall above which forms a bigger arch. @GEO-PAR the detail seems to show the bottom of the Catnic in contact with the top of the stone. The Catnic is more "bendy" than the stone thus the stone could carry a lot more load than you expect not just its self weight. It takes a lot of finesse to design something like this that is not common bedtime reading. I would revisit your detail before progressing. The quality of the stone, type, mechanical properties and knowledge of that is vital. If you have ordered and paid for the Catnic then you need to work around that. This is something that interests me as I love a bit of stone.. but to make more detailed comment I would need to know all the loads from above and how the floors etc are supported on the inner leaf for example. In summary.. I would recommend that you check with your SE that your detail is ok... as it look a bit off to me based on what you have posted so far. Link to comment Share on other sites More sharing options...
jfb Posted October 23 Share Posted October 23 Can you not cut a slot in the back of the stone lintel to fully cover the catnic? pretty sure that was what we did for our French doors (though we had an external steel beam not a catnic and were using bricks to finish) Link to comment Share on other sites More sharing options...
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