Hello all. This is my first post on here so please take it easy on me. I'm soon to be casting a 215x100 lintel to span underneath some bifold doors in a conservatory & wondered what sort of mix would be best. There will be a few steel rods in there so wondering if normal ballast is a bit on the chunky side? Is it better to use just use a cement/sharp sand mix, or maybe cement/sharp sand/gravel?
I am just an amateur but I understand that lintels support brickwork or masonry above windows or doors. A concrete block underneath a door I think is called a step or threshold but I might be wrong. If there are bricks below it I would cast it in situ and I would not bother with any reinforcing as the bricks below will support it. If you want to include some reinforcement I would say three rods would be enough. Normal concrete should be OK . I usually use 20mm stones , sand and cement (2, 2, 1) If you make strong formwork with say 18mm plywood with support behind the stones will just disappear into the mix. Tamp it well down into the formwork to get rid of any voids. Trowel it smooth on the exposed top face. Leave it a day or two before you remove the formwork to be on the safe side. Depending on the width you might find a stone threshold /lintel? in a reclamation yard.
215 X 100 x 2500 (pair of bi- fold doors ?) possibly. At my age I could not lift it. Possibly two young fit guys could. That is why I suggested casting it in situ.
Thanks for the reply PaulBlackpool. There is a lot of made up ground underneath so to save digging down some metres & building up off a footing it was decided to go down this route. It only has to take the weight of the doors & frame. With regards to buying one because of the availability/cost & handling due to the size (4m) & weight it's easier to cast in situ.
Presumably it is on solid ground say at least 300mm at each end? I am not an expert but 4 meters is one hell of a span to be mainly unsupported and I would guess that the section you have indicated would be inadequate. I will leave it to the professionals because I am not sure what you should do.
There are 300mm wide trenchblocks each end for it to sit on, that are built off a good foundation. I was planning on going into these by 150mm each side Forgot to say there will be 3 courses of engineering bricks on top of the lintel (or threshold as you say) and then the door frame.
So it is 215 high and 100 wide and 4 meters long.? Have you had technical advice regarding these dimensions? As other posters have said it might be best to get one made and fitted. Because of the length and load it is imperative that the mix and reinforcemrnts are spot on and only a manufactured product would guarantee that. It is not a DIY mixing job and I would not attempt it. This might be of use:- http://www.trademate.co.uk/ProductExtra/SUP0001/Lintels_Table.pdf
Actual span is 3.7m. I found a company that supplied drawings of a lintel of correct dimensions they produce that showed the 3 rebar positions with accuracy so I intended to copy it. Building regs aren't needed, as its a conservatory. It is my own house, not a customers & as there isn't much loading on it I didn't think to seek technical advice elsewhere. Do you think it would be wise?
I can only repeat what I have said above. I am just a DIYER. Incidentally I presume the conservatory is just to have a one leaf wall. How are you going to support the floor on the infilled/disturbed ground?
You will get the correct off the shelf lintel here, don't bother messing about trying to cast your own. http://www.stowellconcrete.co.uk/precast_concrete_lintels.php
Nope. Cast your pier 8" x 4" if you want, full length. Pier doubles span properties. Mr. HandyAndy - Really
I always thought that most of the weight of bifold doors was taken by the runners at the top? Might be wrong but I thought they usually have runners at the top (which the doors hang on) and the bottom rail was really , only a guide to keep the doors plumb.
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