geoffxr4

My rear extension is well underway and am using 215mm blocks for the walls. I am installing patio doors and the gap is 2800mm wide. I phoned up keystone lintels to see what lintel they recommended but the tech guy asked me what was going above it. I said no blocks, just the flat roof and he said i may not need a steel lintel, a woodern one would probably do it. The ceiling joists of the flat roof run perpendicular to the doors so the ceiling joists would be sitting on the lintel.

any thoughts on whether woodern or steel would be appreciated.

cheers

righthooker

Normaly to get the ceiling height of 2.3m you would have a course of blocks across the lintol and possibly 3 course of brick across the front. In whitch case you would need a85mm cavity lintol 300mm wider than your opening.
Susequently, a 9"x4" timber would give the same affect,but not nessaserily(sp) the required building regs. I take it it is block in and out ?? 85mm cavity?

geoffxr4

i installed a keystone cavity lintel as you describe for the original lounge opening that now leads into the rear extension but my new walls are made from solid 215mm blocks with no cavity and i'm gonna attach laminate insualtion boards to meet insualtion regs. The lintel cost me £350 but i needed it as it had the weight of the loft conversion floor on it.

This next lintel only has the flat roof weight so dont need anything as heavy duty. I'm not sure at them moment whether to have the extension ceiling slightly lower than the original ceiling or not but thought i could put a woodern door frame in to pack it out at the top if needed, if there is a gap between the top of the door and bottom of the lintel. My grandad used to be a builder and recommend i use a plank lintel 215mm x 65mm rated at about 1.4(kN/m) but not sure if this meets building regs or not...?

thanks

dojj

iTrader: (3)

put a metal lintel in and future proof it

you don't need no big heafty concrete reinforced one thgouh

Lee Reynolds

How have you got it passed with solid walls?

Anyway, just get a steel lintel on there for peace of mind.

If you use a timber lintel and sit the joists on that, what is going to cover the outside? As righthooker says.

If you have a 200mm deep lintel, with 200mm ceiling joists, thats a 400mm facia board to cover it up outside! I cant see what else you could do above the door!

geoffxr4

[quote=Lee Reynolds;3864706]How have you got it passed with solid walls?

quote]

I can skin it inside with a 4" block if needed but i phoned hanson who manufacture thermalite and they said i can use the solid 215mm blocks with a laminate insualtion board to meet the building regs.

I'm doing the extension under a building notice so my plans haven't been fully checked but the inspector hasn't said anything to me, BUT he is very laid back and doesn't really seem interested.

WIll i have problem when he comes to sign it off do you think?

g350 aar

iTrader: (1)

i personally would put a steel lintol in, as over time if you used timber the weight of the roof would make the timber sag, and i dont think that a piece of timber spaning an opening that size would pass building control no matter how laid back they r with you

bad boy rs

iTrader: (7)

Timber lintel ! Thats a new one on me, youd never get away with that with my local council. Use a proper metal jobbie, do it once, do it properly

geoffxr4

I'm not tryign to get away with anything, just that's what keystone technical told me when i rang for advice on which lintel to order.

I'll phone teh buildign inspector on monday and see what he wants. then i def can't get it wrong

slimrs2k

If the wall is two skins of blockwork with insulation on the inner leaf, the cheapest way to do it would be to us two naylor r6 precast concrete lintels as the will no about 16kn/m run over that sort of span, which is way less than what the flat roof will be imposing on the walls.

Or

You could use a heavy piece of angel iron propbably and unequal one about 200X150 wiitha weight of about 10 kg/m, or something like a birtley la series lintel or the equivient

If you use a steel lintel, i'm assuming your rendering the outside leaf, make sure its been galvanised post formig otherwise the render acts like a vaccum and pulls the water up behind it and it will make the lintel rust and eventually fail

hope that helps you fella

slimrs2k

another thing as well what thickness of laminated board are you useing you need to get a u value of 0.35w/m2/k or better which gennerally means at least 50mm of solid insulation in a 100mm cavity, so you might find that the board are a bit thicker than you thought, it might be cheaper for you to frame it out and dry line it, that way the building inspector can't complain about it

geoffxr4

Ok, what's the difference? I'm a bit new to all this

I was planning on using something llike kingspan

"Kingspan Kooltherm K17 Insulated Dry-lining Board, an insulated plasterboard laminate "

but yeah, it'll be a couple of inches thick i think.

This stuff can be put on a timber frame or attached using plaster dabs.

cheers

bad boy rs

iTrader: (7)

As its on a building notice with no plans as such, you should try and get as much information as you can from building control that way theres no problems. Every council works with different regs..

D7AKE

[QUOTE=Lee Reynolds;3864706]How have you got it passed with solid walls?

QUOTE]

Regs allow you to have solid walls, but as said need to comply with the U value, 2bh I would use an insulated plasterboard on dab, as it will be so much easier.

Oh and to answer your questions re lintols, if your not needing any brick/block above the lintols either use a box lintol or if the ceiling joists/rafters are coming onto the lintol it must be heavy duty if using a concrete one.

Si

bad boy rs

iTrader: (7)

not allowed concrete lintels on solid block

Lee Reynolds

The timber lintol used as quoted is no different to a trimmer around a staircase pal...

But its the blinding it off outside that im confused about!

Geoff i too am building an extension to my house and i too have only served a building notice. Thats because i know the latest regs and know whats right, i dont on the other hand know what 'you will get away with' and tbh i dont know why your'e trying to get away with it! sorry but solid wall? Sod the insulatiin issues its the damp id be concerned over!

slimrs2k

yes mate kingspan is probably the best thing to use as its the best for insulation i dont think they do one with plaster board stuck to it so you will probably have to frame the wall out with some 50X50 battens and put the insulation betwwen the battens, they should be at about 600mm, then a 1200 guage vapour check to let it breath so that you don't get condesation on the inside of the plasterboard.

slimrs2k

If your feeling rich then you can put 25X25 battens at 90 degrees to the 50X50 battens the put some 25mm kingspan between them: this reduces the chance of cold bridging which means you dont get cold patches on the wall ( this is known as interstichal condensation and shows up as brown patches where the cold gets through) this would obviously increase the u value and make the room a lot warmer. If its a kitchen line it with 19mm marine grade plywood thenplasterboard so you can hang kitchen units from it.

As for concrete lintels in brick walls thats fine, we do loads of barn conversions and refurb jobs at work and line them like i described and support openings with concrete lintels and we have never had one be rejected by building control yet in fact they encourage it. On a new build like yours they should be fine as concrete lintels are properly strong especially over that sort of span and your lining the back with insulation which means there should be no cold bridge over the doors and plenty of strength for snow loads and wind loads, i'd run it past them with what ever lintel you choose first.

As long as the building inspector has been out at the various stages to see the important bits there should be no problems.

righthooker

slim, the kooltherm boards have the insulation on the board , dodle to use but far too exspensive in my oppinion, some one mentioned box lintol, yu wont get one that wide imo.
Just get a catnic(or simmilar) steel lintol and brick accros it , problem solved , it will have the required insulation value and solve the facia issue .
Simple realy.
Got to agree with Lee, not a fan of solid walls, ok the render could be water proofed but not my cup of tea i`m afraid

Lee Reynolds

Then when its rendered theres only one way for any moisture that does get into the wall to go....inside Bad news! Solid walls were ok for old houses when they knew no better!