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Housing - Renovation: Stone Barn Conversion - Lintels over window

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    Hello all, long time no visit the GBF.

    We are just starting a new Barn Conversion project.
    I would appreciate some advice on various issues as it progresses...

    The walls are 500mm thick sandstone.
    There is a badly created window opening put in approx 1960's with a concrete lintel on the outside face and one on the inside face, with bits of timber in between (now rotten).

    We have replaced the outside lintel with a dressed stone lintel to match the original lintels over the doors.
    In the process of tidying up the badly created opening the window will be very slightly wider, which we have allowed for with the size of the stone lintel (150mm overlap on each end)

    What sort of lintel should we install to replace the rest of the bodge job with?

    The stone lintel is 130mm thick/deep so there is approx 370mm of wall thickness to support and then finish off internally with some insulation and plasterboard.

    The length of the lintel is 1800mm (1500mm wide window opening once all tidied up and plumb!)

    A single Catnic type steel lintel of the closest size suitable (heavy duty? extra heavy duty?) or several concrete ones side by side to fill the wall thickness?

    Any thoughts anyone?
    • CommentAuthortony
    • CommentTimeMay 17th 2018
     
    Prestressed concrete for me then lots of insulation that will also mitigate the thermal bridges, the new ones on the inside could go slightly higher up to hello with this

    How are you insulating the building?
    • CommentAuthorDarylP
    • CommentTimeMay 17th 2018
     
    Catnic 'box' lintel.....cuttable, moveable.......
  4.  
    Internal insulation unfortunately. Looking at about 100mm of Kingspan/Celotex/Recticel/Quinntherm then Plasterboard.
  5.  
    a Catnic Lintel like this would almost span the remaining wall depth:
      wide lintel.JPG
  6.  
    not sure if that bit of insulation would do much? Maybe I could squirt expanding foam in to fill the whole thing?
  7.  
    Just had a measure up and the remaining depth is 350/360mm so that picture above could be a good solution.

    I had thought of using concrete but then would I have to use 2 or 3 to fill the wall depth? They only seem to be 100 to 140mm thick. They could indeed go higher up in the wall then I could insulate underneath to meet up with the back of the window.
  8.  
    Dominic,

    (a) Welcome back!

    (b) Please forgive me answering a Q you didn't ask, but re the IWI, are you parge-coating the stone first?
  9.  
    Whats wrong with using stone. Machine square cut its as cheap as chips its only when you want hand dressed stone it starts to get expensive. Fortunately the conservation officer has insisted that all our replacement mullions and lintels are machine cut so that it can be distinguished from the original.
  10.  
    Thanks for the replies.

    Nick, fortunately or unfortunately (can't decide which) a previous owner has rendered the inside walls on the ground floor with cement, probably about the same time as this opening was installed with its concrete/wood/wood/wood/concrete lintels and the concrete boskins to divide the cow stalls (they took some breaking up!)

    John, we used a stone lintel on the outside to match the existing ones over the door openings but at £175 for 350mm high x 130mm thick x 1760mm long, as cut from the quarry down the road (SWMBO dressed the face), I thought it would be cheaper to use a "modern" lintel solution. Plus I don't know how to do the structural calcs if we wanted to use a smaller section of stone.

    I have since asked a very helpful steel lintel supplier and they have done the structural calcs, recommending 2 of their Box Lintels 140mm side by side, so more in line with DarylIP suggestion and they will be easier to manhandle into position than concrete ones.
    I have found these online for about £50 each so ordered them for about £150 all in with delivery. This also gives me the option of filling them with insulation and/or setting them a bit higher up and insulating under the reveal to the back of the stone lintel that is on the outside face of the wall.
  11.  
    Cannot believe the price you have had to pay for your lintel you appear to have been well ripped off. I had 6 mullions a lintel and base packer all for 375.
    • CommentAuthorFred56
    • CommentTimeJun 1st 2018
     
    Sawn stone can be expensive so I am not surprised at the price of Dominic's lintel. Particularly if the supplier is warranting it for the purpose. I have been asked by BC to put steel angle lintels under natural stone because the attributes of stone are not known for certain.
    In terms of the original question of how to deal with the wall thickness. The solution I have used successfully is simply a series of pre-stressed concrete lintel supporting the inner. Three would probably do it. They are cheap and off the shelf. BC understand them. A cavity tray over is a good idea. Not too convinced by the insulation though. These walls are hideously bad on thermal performance and insulating the lintel seems futile. I am committing heresy again but FFS, the walls are dreadful. Cold and damp. The lime mortar sucks in water like a sponge and the air movement through the loose fill inner works like a fridge. The lambda of sandstone is 2.3. A bit of insulation between the lintels is a hiss in the wind.
    If you have the space, build an insulated timber frame inside the shell. Set of off the cold damp walls with a cavity.
  13.  
    Posted By: renewablejohnCannot believe the price you have had to pay for your lintel you appear to have been well ripped off. I had 6 mullions a lintel and base packer all for 375.

    It’s priced by the cubic metre and was about proportional in price to smaller lintels that we had from another quarry about 10 years ago.

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