Which type of lintel should I use??

[henryfire]

I am putting a window in a new opening on fisrt floor of my house. Window will be approx 450mm wide 1m deep. The house is a 1970s brick and block construction with 50mm cavity (unfilled).

Which type of lintel would be easiest to fit? Bearing in mind it will be a new opening.

I have looked at a few types and the 4 inch corrugated type looks easiest, is this for internal use only? I know i will need cavity closers etc.

Any help appreciated!

 

[Richard C]

You must use a structural steel lintel (Catnic) & it must be at least 300mm wider than the opening (150mm bearing on each side); you will also need to fit cavity closers ------ & then get L/A Building Control to inspect the opening & the lintel before the window is fitted!

The window installation is also notifyable work so you will either have to get that inspected & certified after it’s installed or use a FENSA registered installer who will do it for you & issue you with a certificate of compliance; LABC will charge for these inspections & certification.

 

[NS215]

300mm bearing for a 450mm opening ??????????

 

[Richard C]

Sorry that's total 300mm, 150mm each side .

 

[joe-90]

You need to get permission to add a new window first. If you just go ahead and do it you may have to take it out again. The main consideration is whether you overlook an existing window on your neighbour's side.

 

[henryfire]

thanks for replies, i nearly had a heart attack when you said 300mm each side! I understand the 100mm-150mm each side and my BC officer has already specified that. Is a catnic lintel L shaped on the cross section?

Cheers

 

[henryfire]

Sorry just realised that a catnic lintel is probably the type that will have a leaf front and back with a cavity insert in the middle? Could i not use the corrugated type as this would be easier to fit? Then use cavity closers around the frame?

cheers

 

[Richard C]

thanks for replies, i nearly had a heart attack when you said 300mm each side! I understand the 100mm-150mm each side and my BC officer has already specified that. Is a catnic lintel L shaped on the cross section?

Cheers

Yes, extremely sorry about that & sincere apologies, obviously didn’t have my brain in gear! I've put 3 new openings in the 60's property I'm renovating & as far as I'm aware, the 'minimum' end bearing is 150mm so I wouldn't use less than this! As I said, LABC will want to inspect the lintel installation & cavity closers BEFORE the window is fitted.

Catnic (or similar top hat) lintels look like this;

http://www.buildingdesign.co.uk/arch/catnic/catnic.html

I actually did the smallest of the 3 myself as it was on the ground floor (study window about the same size as yours) but using a 350mm diameter, petrol driven, diamond cutter wheel is not for the feint hearted; they can be lethal machines if your not experienced & the dust is unbelievable but its’ all over in a few minutes.

 

[Richard C]

Sorry just realised that a catnic lintel is probably the type that will have a leaf front and back with a cavity insert in the middle? Could i not use the corrugated type as this would be easier to fit? Then use cavity closers around the frame?

cheers

I’m not sure what you mean by corrugated type, doesn’t sound structural to me! The external building walls are both load bearing & structural & on a ground floor or gable end, I don’t think you would have any alternative than to use the top hat type. They may seem to like overkill on the first floor as there is not so much wall above but don’t forget the wall, is most cases, will be providing support to the roof structure above! You could talk to LABC to see what they say but they may require you to provide structural calculations if you want to use anything other than a top hat; BC inspectors are used to them & they are really not difficult to install from inside once you have the opening cut.

 

[henryfire]

Thanks for help, on searching www realised the 'corrugated' type i've mentioned are for internal walls.

I'll use something like this: http://www.buildingsteel.co.uk/lintel_cb50.htm

How do I fit this from the inside?

 

[Richard C]

So are you cutting the opening yourself? How are you doing this?

Once you’ve cut the opening to size, both internally & externally, remove around 160mm of mortar from the external brickwork either side along the top of the opening; this is to allow you to slide the lintel in. You will also need to remove enough of the internal block work below the opening to allow you to feed the top hat section of the lintel into the cavity & turn it so you can slide it into the slots & sit on top of the external brickwork

I find a small angle grinder is very handy for this but I would advise against taking a hammer & bolster chisel to the blocks as this will loosen all the mortar & the surrounding plaster leaving you with much more remedial work. After the lintel is in position, cut some bits of new block to make good at the sides, bed them in place with some mortar under the lintel & re-point the external mortar joint above the lintel.

 

[henryfire]

Richard thanks for your help, I am planning to do this myself, cutting the brickwork with 9" disc cutter, dogtoothing the cut bricks out and turning them around to give the edge a face of brick rather than a cut edge.

I have drawn a picture of what I have understood from your explanation (no laughter at picture!), is that right?
Just tried to upload pic, but realised impossible!

I think i get it though!!

Thanks again

 

[Richard C]

Richard thanks for your help, I am planning to do this myself, cutting the brickwork with 9" disc cutter, dogtoothing the cut bricks out and turning them around to give the edge a face of brick rather than a cut edge.

I have drawn a picture of what I have understood from your explanation (no laughter at picture!), is that right?
Just tried to upload pic, but realised impossible!

I think i get it though!!

Thanks again

My advice is don’t even attempt to dog tooth the external bricks; it’s going to take you forever it’ll be so much extra work, you will never get the mortar pointing (colour) to match & however careful you are, getting the 1/2 bricks back in place to match the originals will be a total nightmare if not impossible.

Hire yourself a Mother F****r, 350mm diamond disc cutter & just slice through it. All 3 of mine were done that way & you need to look really carefully to see they have been cut, even the ground floor one (which I did myself). If you really want to hide all trace of the frog, just stick some quadrant trim around the outside of the frame!

 

[henryfire]

its a first floor window i'm going to do, would it be madness to use a cutter from a ladder!?

fortune favours the brave!

 

[kevnurse]

You really ought to be on a platform. It gives confidence as well as added safety. A 6ft x 4ft working area can be hired for a day, quite cheaply