fitting timber lintel to top of wall.

[colliefish]

Hello people,
I'm building a single story largely glazed extension with a flat fibreglass roof.
BC has said i can use wooden lintels to go over the window and door openings. My question is how do i attach the 200mm timbers to the top of the cavity wall.
I was going to use the L shaped straps to the internal leaf and then down onto the top of the joist.
I've attached a rough drawing.
Thanks for any advice you guys can offer.
Mark.

Untitled

• colliefish
• 29 Dec 2013
• 1

 

[KenGMac]

colliefish, Hi

On this board after a couple of days and no reply? WOW

WOW indeed not exactly what I would call a "conventional" design?

1/. Suggestions as follows?

A/. Using galvanized "coach Bolts" you firmly fix the two lintels together, both the outer and inner. If you fit these "Coach Bolts" with the heads into the cavity so that they will not be visible from either the room side or the outside then that should be aesthetically "pleasing" the use of washers under the heads of these devices is advisable.

B/. Should these things not be "designed" by a competent "Engineer"?

C/. Turning now to ensuring these two "independent" "beams" in some way act together? and support each other? And at the same time have an inherent "monocock" function?
The insertion of noggins between the pair of Lintels would appear "prudent"? Plus at these points it could be thought that some form of firmly fixing the two twin Independent "Lintel units together" is worthy of consideration?
the use again of suitably long "Coach Bolts" on this occasion inserted from the "inside" [plus washers under the heads of the bolts] could form a reasonably "Stable" beam like system?
The bolt heads could be left "proud" of the surface? [dependant on surrounding "finishes"] or recessed and the circular holes filled with "Plugs" of the timber to which it has been fitted?

As for your "Idea" of hold down straps, YES! BUT! ?
How about fitting these straps, not only over the Inner lintel, BUT extending to fit over the pair of twin lintels? the thinking here is that if you follow the above, you are constructing a twinned two part "Beam" "System" comprising of four individual "elements" all firmly tied and bonded one to another?

Following on from the above [If you are still awake ! ! !] if you fix these hold down straps on or as close as you can to the Noggins and coach bolts between the outer and inner lintels the overall tie down and improvement in overall "strength" of the entire design should be improved.

Conversely, "obviously" depending on where you can get a really good solid Hold down fixing could dictate where the hold down straps Et All are fitted?

Hope this has given some Ideas?

Are you surer that you should be asking such questions on this Forum, after all there are very few Structural Engineers in here, just a load of folk with a vast insight to the "build Process" ?

Cheers.

Ken

 

[tony1851]

colliefish, Hi

On this board after a couple of days and no reply? WOW

 

[colliefish]

Hi Ken,
Thanks for the reply.
Building control had told me the size of the timbers but not their prefered meathod of fixing down to the wall or wallplate.
Your answer has been most helpful and from what I understood is what I had in my mind.
I've emailed the drawing to my building inspector as I dont want to do anything unless he is happy. Weather has stopped play again! so I can patiently wait for his reply.
Thanks again.
Mark

 

[themiddleagedun]

Why not just keep it simple...? Use a conventional steel lintel (IG/Catnic type) over the openings with a couple of course of face brick on the outside and a course of block on the inner leaf with a timber wallplate on top?

 

[colliefish]

I know that would be the best method, I was just trying to keep down costs at Catnics seem to be pretty pricey. Its still something I'm considering though. Thanks for the reply.

 

[colliefish]

another question regarding the catnic idea,
I'm actually building a single story extension on the back of my house, there will be windows running from the house wall 2.4m along one of the extension walls. Would I need to take out some blocks/bricks from the house for the lintel to sit in, or is there an alternative meathod of attaching it to the house?
cheers
Mark

 

[r896neo]

Have you considered how you intend to finish these timber lintels internally and externally?

 

[colliefish]

Extenally timbers would be hid by fascia boards, internally they would be partly within the ceiling and what is exposed would be covered by plasterboard.

 

[catlad]

I am not sure I understand the question. Your drawing shows 8x2" treated timber doubled up on top of each wall? are these walls made of masonry?

 

[Alastairreid]

Use concrete lintels, even cheaper than the wood.

 

[colliefish]

Hi Catlad,
yeh the walls are masonary.

 

[catlad]

Screw them together with the relevant space in between filled with celotex and the odd noggin, your roof boards and windows should do the rest.

 

[colliefish]

Thanks Catlad

 

[wrightwoodwork]

Untitled

• wrightwoodwork
• 30 Dec 2013
• 1

I've done a sketch for you showing the details of timber lintel details in timber kits hope it helps you to understand how it should look all timbers should be c24. The outside wall can have a concrete lintel or a steel lintel. Must be seated on at least 100mm either side. I build kits every day your idea with the restraint strap won't work and isnt needed. Nails should be 90mm at least for a nail gun approved to eurocode 5 class2 service. Lintel needs to be double nailed every 150mm each timber lintel. The cripple studs need to be double nailed every 300mm