Structural calcs

ds1980

Do I need to have these as part of our new extension? BC haven't asked for them. We are not removing anything that isn't already supported but there are bifolds with structural opening of 4.08m going in. Builder has bought a steel lintel possibly catnic (4.5m) but me being me i like to check these things and wondered if that was right. I carried it in with one other person seemed a bit light considering the weight going on it? I remember when we built the loft the steels were massive!

Extension is about 8x4.5m. Lightweight breeze internal, brick facing on rear and one side and concrete breeze on other side. Will have pitched roof With 49ers

Just had a look at spec of bifold s and were getting smart system which looks like they aren't top hung as it were so assume this may make a difference?


Ta

brightontraveller

Structural engineer normally calculates size lintels. Not a builder (catnics are a brand that makes lots of different types of lintels). Can’t see building control passing it without all necessary calculation? It’s a pain in the butt to do so retrospectively and cost a lot more normally ?Is builder using a horse to put them in place

ds1980

Ha. That's why I asked. Will call building control. They've had plans from me but didnt ask for any calcs for structural openings. Cant get a horse round the back so will have to work out an easier way.

Furts

Be very careful here. I have a Catnic spanning a kitchen opening of around 2800. This is a heavy duty lintel that weighs so much that two people were required to place it. The lintel is almost at the limit of standard Catnic lintels, and even then has to be ordered and made in advance. Once one exceeds around a 3000 opening this is into heavy weight territory, and it may be more cost effective to get steels built in.

Your builders proposition is worrying.

ds1980

Thanks for concerns. BC say i don't need calcs. IG have specced the opening and construction and the lintel is fine. Doors are bottom hung so no additional weight on lintel that way.

Lets hope it doesn't all fall down

System

I have never heard building control say they don't need calcs for a lintel!! especially one as large as 4m wide… Surely they want at least details from the lintel manufacturer? Catnic iirc have standard tables for their lintels but BC still always ask for that information…

Has anyone designed your foundations? or is the builder just digging to x depth and hoping for the best?

(also the lintel is not there to support your doors)

brightontraveller

Installing a lintel is structural or structural alteration normally covered under Part A of the regs.
There are exceptions with routine repair/maintenance etc therefore not a structural alteration, so not under there remit replacing like for like etc , can’t really see that being the case for a new extension ?

Some will say if you put a lintel of size x with manufactures literature etc in we will pass it but often x is completely oversized to cover all ?

Although doubt they bring out any enforcement action it may show up on local searches as unauthorised work? Which brings whole new level of fun to the table if you were to sell etc defiantly I’d ask for confirmation in writing?

Furts

the_r_sole wrote: »

I have never heard building control say they don't need calcs for a lintel!! especially one as large as 4m wide… Surely they want at least details from the lintel manufacturer? Catnic iirc have standard tables for their lintels but BC still always ask for that information…

Has anyone designed your foundations? or is the builder just digging to x depth and hoping for the best?

(also the lintel is not there to support your doors)

I second this. A nominal lintel, such as that offered by your builder, might be OK if your new opening is in a non load bearing location, such as an internal block wall built off your ground floor slab. But weight above, and deflection, need consideration on such a large opening even if the wall is not load bearing.

If you are supporting two leafs of wall this is a give away sign that you have a load bearing wall. To this it should be remembered that bi-fold doors are usually on the outside walls, or where a previous outside wall is. These situations require design.

Give careful thought to your situation.

ds1980

thanks again guys.

Builder has been building houses for nearly 60 years. Very old school but i trust him implicitly (he's my uncle) I did the foundations and they've been signed off by BC.

I spoke to IG who manufacture the lintel we're using. They have all the details and they assured me that the lintel in question would suffice our needs.

Building control said that I "would" normally require calcs but as this is a new extension made of standard construction that supplying them the details of the exact lintel should be fine. They already have the plans to the extension and theyve been told it was l1/s100 4500mm lintel. I have just received an email from them saying that the lintel specced will be fine taking roof loading only into account which is what there is.

The bi-folds people told me that the doors are not weight bearing as such from the top as they are supported underneath which shouldn't make any difference to the overall effect of the calcs for the steel.

I'm happy to speak to a structural engineer but building regs are fine and they will sign the job off ultimately, as are the lintel manufacturers and the builder whose been building houses for 60 years. They make these lintels to a certain standard anyway so cant really see the issue but i'm happy to get a bit more peace of mind i suppose by consulting an engineer?

Probably should be less laid back about my roof caving in!

Furts

ds1980 wrote: »

thanks again guys.


I spoke to IG who manufacture the lintel we're using. They have all the details and they assured me that the lintel in question would suffice our needs.

Building control said that I "would" normally require calcs but as this is a new extension made of standard construction that supplying them the details of the exact lintel should be fine. They already have the plans to the extension and theyve been told it was l1/s100 4500mm lintel. I have just received an email from them saying that the lintel specced will be fine taking roof loading only into account which is what there is.

I'm happy to speak to a structural engineer but building regs are fine and they will sign the job off ultimately, as are the lintel manufacturers and the builder whose been building houses for 60 years. They make these lintels to a certain standard anyway so cant really see the issue but i'm happy to get a bit more peace of mind i suppose by consulting an engineer?

No need for the cost of a Structural Engineer, because an enquiry to IG should you the calcs and proof that you require. Bear in mind that Buildings Regulations may change their mind , or allocate a different inspector before you complete. Hence you have to protect your interests.

The fact that the builder has been working for 60 years is admirable, but that does not mean that what he does is always correct.

Finally, it is your role to apply for and monitor the Buildings Regulations. It is not the responsibility of your builder/uncle. Hence, again, protect your position.

*~Zephyr~*

ds1980 wrote: »

Builder has been building houses for nearly 60 years.

You have an 80 year old building you an extension? I hope you give him plenty of tea breaks! :rotfl:

ds1980 wrote: »

I'm happy to speak to a structural engineer but building regs are fine and they will sign the job off ultimately, as are the lintel manufacturers and the builder whose been building houses for 60 years. They make these lintels to a certain standard anyway so cant really see the issue but i'm happy to get a bit more peace of mind i suppose by consulting an engineer?

If you phone a friendly local Engineer and run it past them, they will probably give you a bit of verbal reassurance on this for free, if it will help you sleep at night. They won't put pen to paper and give you a report without changing you for it though.