watsonpj
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| posted on 6/11/13 at 08:26 PM |
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Packing under rsj
Ive fitted an rsj over a window intel but am unsure what to pack underneath it to fill the gap. As the concept is the steel is meant to take the load
do you just put insulation in there and cover over with plasterboard or do you pack in with slates as ive seen on some online sites.
Cheers Pete
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JoelP
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| posted on 6/11/13 at 08:39 PM |
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Need details. Do you mean a proper rsj, or a folded steel lintel? And what do you mean when you say that you have put an rsj over a lintel, do you
mean replaced or sitting on it?
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mookaloid
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| posted on 6/11/13 at 08:40 PM |
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You need slate under the ends where it takes the weight because sand/cement mortar might crumble. If you are just covering it up after you have made
it structurally sound then if you insulate it under the plaster board then you will reduce the possibility of condensation in that area.
Not sure why you are putting an RSJ over the top of an existing Lintol though...
"That thing you're thinking - it wont be that."
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Ben_Copeland
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| posted on 6/11/13 at 08:51 PM |
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Slate packers are a must otherwise it'll sag and you'll have cracks everywhere or worse
Ben
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Smoking Frog
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| posted on 6/11/13 at 08:57 PM |
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I would bed it on some mortar on top of the brick. If it's a heavy lintel and soft mortar the mortar may ooze out, you could use slate as
already mentioned or some red query tile material. Should sit on a full brick each side as well if I remember.
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nick205
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| posted on 6/11/13 at 09:00 PM |
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You need to post some pics up so we can see what you're up to.
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Smokey mow
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| posted on 6/11/13 at 09:51 PM |
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Pics would certainly help to visualise the problem.
Assuming we're talking about under the end bearings an RSJ would normally be packed with metal shims rather than slate, however it's
common to use slate as a packing on top of the beam between the beam and the brickwork above, any remaining gaps etc should then be drypacked with
mortar.
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SteveWalker
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| posted on 6/11/13 at 10:37 PM |
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Not sure whether it applies to RSJs over windows, but IIRC RSJs where a wall has been removed internally have to be covered with two layer of
plasterboard, as they weaken rapidly in a fire and the plasterboard insulates it.
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watsonpj
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| posted on 6/11/13 at 10:54 PM |
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Sorry guys its a proper universal beam which has a flitch sitting on it as the lintel wasnt strong enough to take the new additional loads. Ends are
sitting on metal shims as per structural engineers instructions. I just wasnt sure what to do in the middle where there is a gap below the ub to the
lintel below. As its too strength an area that is seen as a weak i was unsure if packing with slate was the right thing to do and wondered if just
insulating and the covering over with pkasterboard might be better as there would be no load transfer to the lintel that way.
Cheers pete
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Smokey mow
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| posted on 6/11/13 at 11:47 PM |
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The normal design deflection at the centre of a UB would be a maximum of 3mm per metre span.
Cavity Lintels are designed to have a proportion of their loads shared between the interal and external flanges (catnic lintels for example are
either 1:1 or 19:1 ratio) this is typically to ensure the lintel desn't buckle by having all of the weight only on the one side.
The deflection of a UB over the width of a window opening will be quite small so shimming to the lintel below it will ensure that the lintel is
lightly loaded by the deflecting steel on the inside lead to counter balance the weight of the brickwork on the outide leaf.
All that said, if in any doubt at always call the Structural Engineer for advise.
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Not Anumber
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| posted on 7/11/13 at 10:31 AM |
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I always mount the ends of an RSJ on engineering bricks. I normally keep the thickness of mortar on that layer quite thin and prop the RSJ whilst the
mortar is hardening off. Shim with slate rather than making the mortar too thick on one side.
If you have fitted a new load bearing lintel above an old one then the higher, newer lintel will be doing most of the work. If the lower, older,
lighter lintel is firmly suported and fully sound you can fill the gap between them with a few dobs of mortar with squirty foam filling the rest of
the gap.
There may be instances where a structural engineer would reccommend joining an upper and lower lintel but this would normally only relate to full RSJs
and they would give specific instructions if this needed to be done.
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watsonpj
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| posted on 7/11/13 at 11:21 AM |
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Thanks guys ill just pack in loosely with foam and mortar then as all calcs are for ub taking the full load.
Cheers pete
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