concrete lintel question

[andymarshal]

Hi, on the back wall of my house i have a large widow about 1000 wide by 1500 high. i would like to take this window out to create an opening (new extension being buit on the back)

The house is a 2 up 2 down 9 inch solid brickwork - if i use 2 concrete lintels at say 1700 long - would this be sufficient support.

Thanks guys
Andy

 

[Richard C]

Andy
I recently removed 2, cast in situ lintels from an old single story extension, one was over 2m long, at least foot square & must have weighed half a ton & no amount of persuasion would get it to break up; In the end I ended up completely demolishing the wall & rebuilding it with a steel Catnic for the new French door opening & getting it all retrospectively inspected & passed by Building Control!

The easiest way for you would be to create an opening under the existing 1000mm window & leave the current lintel in place - assuming there is one! This would also save you the hassle doing calculations for the new lintel & involving BC in inspections; but if you want to create an opening wider than the current window, I wish you the best of luck in removing that old concrete lintel! In your case (with a solid wall) I would go for 2 steel box lintels or RSJ’s (of suitable size) bolted back-to-back rather than use concrete.

 

[andymarshal]

hi richard, thanks for the reply, at the moment there is a timber lintel with a brick work (original 1880) arch above it. the timber lintel doesnt seem to be holding anything at the moment so it should be easy to rip out. i presume the arch is doing most of the work at the moment?

Richard is there ny reason why you wouldnt use concrete as this is more cost effetcive than say a rsj

Thanks
Andy

 

[Richard C]

Andy
The brick arch is almost certainly holding everything up & should happily continue to do so if you intend to stick with the existing opening. But if you don’t, at least you won’t have the same problems I did with removing a cast-in-situ, reinforced lintel! I’m doing a lot of refurbishment & improvement work on my 60’s property & I’ve learned the hard way that it’s easier to modify your ideas slightly & work with what you’ve got; you can achieve almost the same thing, it’s much quicker & far more cost effective!

The reason I would use steel over concrete should you go for a wider opening is that, for a given load bearing capacity, it’s much stronger, lighter & therefore easier to manage. I’m only a mechanical engineer with a working knowledge of structural engineering principles but I’m not sure pre-cast concrete lintels would be strong enough over a new opening of any width in a 9” solid wall, although others may well put me right!

 

[Richard C]

Andy
The brick arch is almost certainly holding everything up & should happily continue to do so if you intend to stick with the existing opening, did you intend to use the concrete lintels as merely a liner? But if you don’t, at least you won’t have the same problems I did with removing a cast-in-situ, reinforced lintel! I’m doing a lot of refurbishment & improvement work on my 60’s property & I’ve learned the hard way that it’s easier to modify your ideas slightly & work with what you’ve got; you can achieve almost the same thing, it’s much quicker & far more cost effective!

The reason I would use steel over concrete should you go for a wider opening is that, for a given load bearing capacity, it’s much stronger, lighter & therefore easier to manage. I’m only a mechanical engineer with a working knowledge of structural engineering principles but I’m not sure pre-cast concrete lintels would be strong enough over a new opening of any width in a 9” solid wall, although others may well put me right!

 

[Richard C]

Don't know what happened there, I was trying to edit!

 

[Static]

In short if it 'aint broke dont fix it. When you remove the old window (which im assuming you are replacing with a door) check the existing timber lintel for signs of damage/rot, treat it with a preservative, then cover it up again and install the new door.
If it is unsound then post some photos.

 

[nobody]

Just be careful.

Arches are strong but they can slip, make sure that the mortar in the arch is good before you remove a linel below it. You could find that the lintel is supporting (not supporting the weight of the wall but just holding the arch in place) the wall. You can have a situation where the arch needs positional support. perhaps a steel strip inserted directly under the arch stones to prevent slip - it wouldnt need to take serious weight just stop the arch slipping.

 

[NS215]

hi andy

if you need to take the opening higher then 2 100x150x1350 lintels will do the job as you only need a 150mm bearing either side

if the existing opening is high and wide enough then just stud out the the arch to make it flat and treat the timber as suggested

 

[andymarshal]

hi guys, thanks for the replies -

The window is coming out to make a walk through, upon further inspection, the timber lintel is the same length as the window frame so it is doing sod all.

The arch looks to be in good structural condition and there are no signs of cracked brickword/movement so i think the best route is to place the concrete lintels at the required height and then brick up to under the arch.

i pressume this is the best way as the arch and lintels will be supporting the wall

Any thoughts?

Andy

 

[NS215]

yes if you can get the height leaving the arch in then fine put concrete lintel under and build up under the arch and on the inside skin take the timber out and put a concrete lintel in there as well

very simple task

 

[andymarshal]

thanks guys, just wanted to check before i attempt the job.
Cheers

Andy

 

[WabbitPoo]

first of all, I am not a builder, OK?

Is this opening then in an outside or other supporting wall? I would bet my dog's pocket money on it being subject to BCO approval, if not planning. Please correct me if wrong. If that is so, what are they expecting you to put up over the opening?

 

[Richard C]

Providing it’s not listed & you don’t live in an area of special or architectural interest, the opening itself will not be subject to BC unless you make it bigger & fit a new lintel; how you close the now exposed cavity below the window cill is though & what ever the new hole in the wall leads to may well be but not if it’s a conservatory (yet); but if it is a conservatory, you must have an external grade door fitted between the 2 rooms for insulation purposes (most fit the cheapest doors they can find & take them down as soon as it’s been inspected). But then again what goes into the conservatory may well be subject to BC (electrics, heating etc). You don’t need PP for a conservatory unless it’s larger than 30 sq/m (I think) or more than a certain % of the current size of the house! & possibly a few others as well, I can’t remember!

It’s all a bit of a dog’s breakfast & can get a bit complicated & even the local council get it wrong if you just ring up & ask; sometimes you can get the wrong advice (depends on who answers the phone) so always put it in writing or go visit a BC officer in person. But it's always worth checking everything out yourself, don’t rely on advice from small builders (or any builders come to that!) as many doing small jobs of this sort either don’t know or don’t care & will say you don’t need PP or BC when in fact they know full well you do. You will end up picking up the tab as it’s the poor mug of a home owner who is responsible. I’ve just spent months trying to get a registration certificate out of OFTEC because one of their certified installers just did not want to pay the works notification fee for my new tank installation. Threats from Trading Standards & from OFTEC itself about withdrawal of his OFTEC registration finally did the trick but a lesser mortal may well have given up along the way, I even had to put him straight on some aspects of the installation he was trying to cut corners on; a total bl**dy cowboy!