Lean to Extension on Rear of House

[bricky48not]

Hi There, I'm in the process of producing drawings for the above to comply with Building Approval -even though the Extension should be ok for the Planning permission because it does not protrude more than 3m from the back of the existing house, is 4.2m wide and agrees with the ruling of : Height of Eaves, Height of Roof etc.
The outer leaf of the new cavity wall is to be 'facing brick'.
What do you think that my inner leaf should be please?
Many Thanks, Keith

 

[John D v2.0]

Lightweight Blockwork is traditional nowadays. Or you can use heavier concrete blocks if you want to hang anything super heavy on the walls.
The important part for labc is that you calculate u value for the wall.

 

[bricky48not]

Thanks for That, apart from perhaps a Radiator I'm not too worried about hanging anything. about to cover the u value aspect, what about a block with celotex attached? Cheers again.

 

[freddiemercurystwin]

This is gonna be a very long thread .....

 

[John D v2.0]

Thanks for That, apart from perhaps a Radiator I'm not too worried about hanging anything. about to cover the u value aspect, what about a block with celotex attached? Cheers again.

Yes, however BC will want way more information than that to be satisfied that the proposed construction meets building regs.

If you're not familiar with building design and the regs, you might want to get a proper designer involved, as this method of asking questions one at a time has a drawback as observed by the below poster...

This is gonna be a very long thread .....

 

[^woody^]

Lego would be nice. As long as you have have enough of the same colour - it's annoying when you have to use a random blue brick in the otherwise yellow wall.

 

[bricky48not]

Oh...I'm really sorry Lads, Have I asked something of you that was out of order or stupid?
I didn't mean to make it a long thread. The only thing that I asked for was for some advice on the inner leaf for my drawing so that I could determine the size of the foundations and depth.
I didn't intend to repeatedly ask you about any other spec regarding visqueen, or sand binding etc, or what size B.A.T. multi nail Rafters system or Joists or what size Ridgeboard, wall plate, facia, soffit -or what type of insulation I should use in the ceiling. Many Thanks again for your advice.

 

[noseall]

The only thing that I asked for was for some advice on the inner leaf .

Brick external leaf, block (3.5n) inner leaf with 100mm full fill Drithem cavity. Overall wall thickness 305mm. Standard width (600mm) foundations unless requirements for clay heave are requested. Don't try and trick it up with unnecessary gizmo designs else the brickies will leave site quickly.

 

[noseall]

Oh...I'm really sorry Lads, Have I asked something of you that was out of order or stupid?

I think the guys are dreading you asking about each individual inner leaf materials option one at a time and one post at a time. They kinda envision you watching Grand Designs with a North Korea style notebook in hand, ready to pounce on the DIYnot Q&A forum.

We don't get paid an awful lot you know.

 

[John D v2.0]

Oh...I'm really sorry Lads, Have I asked something of you that was out of order or stupid?

No need to apologise for woody, that's his hobby

The only thing that I asked for was for some advice on the inner leaf for my drawing so that I could determine the size of the foundations and depth.

I doubt the materials above will influence that for domestic, unless you're building a block of flats the foundations will be based purely on ground conditions.

 

[^woody^]

What do you think that my inner leaf should be please?

If you are not doing a timber frame, then it will be either block or brick.

Most likely block, and then you get to choose whether it is concrete or AAC. Then you get to choose whether it's 100, 110, 120 or 150mm thick.

All this depends on the insulation you propose to use and whether you want to wet plaster or plasterboard it- and whether that will be insulated or not too.

So its not just a case of "what should I use for the inner leaf". You need to consider several things for specific reasons and not just pick materials in isolation and throw them all together. Cost and availability come in to it too, and buildability if you are DIYing or picking builders who may not be too clued up in certain methods.

And BTW, you would not normally specify "facing brick" as thas meaningingless. There are concrete bricks and ones made from calcium silicate along with the more common clay. You need to specify a standard for whatever brick you propose.

 

[Notch7]

Hi There, I'm in the process of producing drawings for the above to comply with Building Approval -even though the Extension should be ok for the Planning permission because it does not protrude more than 3m from the back of the existing house, is 4.2m wide and agrees with the ruling of : Height of Eaves, Height of Roof etc.
The outer leaf of the new cavity wall is to be 'facing brick'.
What do you think that my inner leaf should be please?
Many Thanks, Keith

The most conventional masonry construction to elemental values is as per Noseall states: brick --100mm cavity with full fill drytherm or rockwall cavity batts --lightwieght blocks inner skin.

Generally foundations are simply trench fill concrete, usually 600mm width (the width of a standard digger bucket). Nominally 1000mm deep from ground level. Note depth will be influenced by ground type and trees/hedges in zone of influence (up to 25m from memory). Do your research now, ask neighbours on ground type if they've had extensions and what depth they had to do. Better than find out when the BCO arrives on site and says; Mmm I think you need 2.5M deep footings!

Either local authority can do building regs or you can use a private licensed contractor (BBS building control for example), who you find may be more helpful.

You will need to include all elements of the building regulations that apply to your construction in order to get through the plan checking stage.

If you are doing the building regs yourself, do make sure you find out if there are any drains or services running near where your extension is going to be. I got involved in a job once where the client applied for regs, builders started only to find there was a drain 3.2 Metres down! Manholes were some distance away in neighbouring properties. Also just done a job where a power cable was in the footing line, but no evidence of any cables on any power network drawings.

Dont get confused between planning and building regs!

 

[bricky48not]

Thanks for all your advice

 

[pilsbury]

Question has been answered but some advice from another novice who is nuts deep in his extension. Reading and perseverance is key if you’re doing it alone. YouTube, this forum, google and building regs need to be hammered on a daily basis. You’ll get loads of information, lots conflicting but then you’ll see a pattern in how it’s done.

You’ll have some dark days, lots of standing back and shaking your head about why you started this thing in the first place. That’s where the perseverance comes in. Just keep thinking how much it would have cost to get someone to do it. By my calcs, 4 times the cost of materials if you’re crafty.

Good luck.

 

[bricky48not]

I really appreciate that Pilsbury. Yes you are dead right! I'm a fellow rapidly approaching 70 and just after retiring I had to restore a 3 storey Victorian Terrace house which had nothing done to it since 1875. It was an Uncle of mine who had the House taken off him by the Council to pay for his Care home fees. He hadn't wrote a will and was fretting about all his belongings in the House. So to cut a long story, I bought it back off the Council and it took 5 years to do it up. I did not start the restoration until my Uncle had passed away. As you say, I did get help off this forum and Youtube etc, and I was so proud of it when I finished. I sold it with no gain but couldn't care less. God Bless you mate!