Basic building regs question...

[Beanyboy2802]

Hey all. 

I have a question about the building regs. I'm in the early stages of design for a new house, and just starting to wrap my head around building regulations - and there's a clause in A1/2 (clause 2C17) which states this section does not deal with walls longer than 12m, in reference to exterior or structural walls. 

The clause does state that the 12m length is to be measured from centre to centre of buttressing walls - I assume that includes where the exterior wall turns a 90 degree corner.

So if I make the back wall of the garage (which is half the depth of the long exterior wall in question) a structural wall, does this effectively mark the the measure point for the 12m limit? 

I.e., I measure 6m from my garage wall to the front end of the long wall, then 6m from my garage wall to the back end of the long wall. 

Thank you for any help you can provide - it is much appreciated. 

[ETC]

Can you post a sketch of what you mean including length and height?

[Beanyboy2802]

2 hours ago, ETC said:

Can you post a sketch of what you mean including length and height?

 

Sure - forgive the roughness of the extract, it's barely a started drawing yet, let alone finished! 

 

I've removed interior stud walls for clarity. Showing planned doors and windows in the heavy walls as approximate positions. Nominal wall width of 350mm shown, based on other planning drawings I've seen. 

 

Wall height is a normal 2 story house - hoping for 2.4m ceilings, but not figured that out just yet. Could end up being the end of the roof, so consider that height as worst case. 

[George]

In short yes .

 

The wall length of 12m is for a 'wall panel' which on your sketch is the 6.1m and 7m. This is because the internal wall provide a buttress support to the external wall.

[Temp]

I think you might need a movement joint. 

 

This is from the NHBC..

https://www.nhbc.co.uk/binaries/content/assets/nhbc/tech-zone/nhbc-standards/tech-guidance/6.1/movement-joints-in-masonry-walls-.pdf

[Beanyboy2802]

1 hour ago, Temp said:

I think you might need a movement joint. 

 

This is from the NHBC..

https://www.nhbc.co.uk/binaries/content/assets/nhbc/tech-zone/nhbc-standards/tech-guidance/6.1/movement-joints-in-masonry-walls-.pdf

Yes, I'd seen this - thank you for the link, because I'd lost it lol. 

I'd considered putting the expansion joint somewhere near the middle of the wall, which puts close to the buttress wall. Do I need to consider the effectiveness of the buttress wall when determining the location of the expansion joint? Would it be best to stay away, or make use of the buttress in some way? 

[Beanyboy2802]

9 hours ago, George said:

In short yes .

 

The wall length of 12m is for a 'wall panel' which on your sketch is the 6.1m and 7m. This is because the internal wall provide a buttress support to the external wall.

Brilliant - thank you. I assume the positioning of the door doesn't make much of a difference. 

Does the buttressing wall need to be the full height of the exterior wall? Even if the exterior wall goes up to the eaves of the roof? 

[George]

The height of the wall will make a difference. If it doesn't go full height then the wall at first floor will need to be subdivided some other way to comply with Part A, else it'll need an engineered solution. 

 

These sorts of things (Inc the movement joint) are detailed design things which an engineer can help you with once the layout is sorted. 

Edited March 17, 2023 by George

[ETC]

[Dave Jones]

12 hours ago, Temp said:

I think you might need a movement joint. 

 

This is from the NHBC..

https://www.nhbc.co.uk/binaries/content/assets/nhbc/tech-zone/nhbc-standards/tech-guidance/6.1/movement-joints-in-masonry-walls-.pdf

 

not allways, if you have windows in that elevation for example you can get away with it. They look terrible so avoid.

[Beanyboy2802]

10 hours ago, George said:

The height of the wall will make a difference. If it doesn't go full height then the wall at first floor will need to be subdivided some other way to comply with Part A, else it'll need an engineered solution. 

 

These sorts of things (Inc the movement joint) are detailed design things which an engineer can help you with once the layout is sorted. 

Thankfully the design I have, both sides will be easy enough to provide a structural buttress wall over both floors, and if necessary it can go to the full height of the house. 

Some minor mods to the layout and I think my wall length problem is resolved. Obviously, the experts will tell me otherwise if I have a bad steer in there, when I get to that stage!

Thank you for the advice, much appreciated. 

[Beanyboy2802]

9 hours ago, ETC said:

This is useful - I'll have a look for this section in the regs, cheers. 

Top of my head, the question that comes to mind is, the first sentence of 4C.18.

In my arrangement above the garage obviously has an adjoining internal wall on the left, so bot ends are supported.

But at present I have 4m on the first floor which doesn't have a supporting wall at its far end. 

Does the internal buttressing wall, of 4m length, need a buttressing wall of its own? If so, what is the maximum length the internal structural wall can be without its own buttress/adjoining wall at the far end? 

[Beanyboy2802]

33 minutes ago, Dave Jones said:

 

not allways, if you have windows in that elevation for example you can get away with it. They look terrible so avoid.

Using doors and windows as movement joints is an interesting suggestion, thank you. 

Can't say I know much about the aesthetics of it, so I'd have to look into that - but I think I'm a ways away from that just yet! 

[Temp]

If you do need a movement joint you might be able to partially hide it behind a rainwater down pipe.

[Beanyboy2802]

Another basic regs question.

The regs say a floor span can only be a maximum of 6m. I presume that can be 6m from an internal wall, not 6m between two structural walls. Is that right? 

The way I'm reading this, it feels like every wall in the house will need to be structural, which doesn't feel right! 

[saveasteading]

Floor joists must sit on structural walls, so yes, some internal walls will be structural, with footings.

 

There is nothing magic about 6m, but it is the standard maximum for timbers at a merchant. Longer is special.

But at 6m clear span  joists get very deep, so you are getting into intermediate steel beam territory, or fabricated (and deep) joists.

[Temp]

+1 Perhaps run a steel across the other way so your timber joist span is halved.

Edited March 19, 2023 by Temp

[Gus Potter]

On 16/03/2023 at 20:35, Beanyboy2802 said:

I'm in the early stages of design for a new house

Fantastic.. it's great fun, sometimes frustrating but sounds like you are putting a lot of thought into it and reading up, reading around and expanding your knowledge. You'll reap the rewards of your efforts.

 

On 17/03/2023 at 21:56, George said:

else it'll need an engineered solution. 

The best thing you can do is to post what you have in mind in terms of conceptual design. Don't be embarressed if you think they are rough looking (you want to see some of mine!) and you're not under examination.

 

If you do this you'll get loads of help, ideas and suggestions.. then you can pick out the best bits, discard the ones that don't suit.

 

For all... here are two key points:

 

Many two storey modern houses have big open plan spaces on the ground floor and big glazed openings. While this is ok and can be designed for SE wise if you don't want to break the bank then there are a couple of things (not least but start here) that you want to aim do. Try and avoid a layout that results in the roof loading landing over / near the middle of the big glazed openings unless it is spread out. With big open plan spaces you often have a floor (maybe another?) above that may need to have long spanning joists thus you may need to split up the joist span with a transfer beam.. try and avoid transfer beam end loads landing over glazed openings. You can do it.. it just cost more as you need to control deflection. Also big openings reduce the amount of solid walls you have to stop the building moving sideways as per next point.

 

This other key point is what we call lateral (global / overall) building stability.. we need to design the house so it does not move sideways in the wind. This is different from "buttressing" covered in the regs for small buildings. Yes.. if you add up all the small buildings guidance bit you could well end up with every wall being structural.. and then find that non of it works anyway in terms of point loading from transfer beams and global lateral stability.

 

The above said you are on your way (well done you taking the time to study) by recognising that the individual wall panels need to be braced to stop them from buckling sideways, out of the vertical plane. The buckling effect is commonly caused by two things.. the fact that the vertical load from above does not sit directly over the centre of the wall and by addition of wind suction / pressure loads.

 

And you have movement joints.. it's quite complex to arrive at a reasonably economic solution and all this changes depending on the type of construction.. masonry, timber frame, SIPS, ICF. 

 

Roughly concrete blocks shrink after laying and clay bricks swell over a long period of time. But both move about depending on the temperature. Generally I get nervous when a block wall gets over 5.0m long.. and if I was designing using a traditional English clay brick I would not stretch it to 9.0 m without a movement joint on a self build unless I new exactly what brick you were using and had control over the mortar. Basically it's self build and the brickie may be hand mixing so there lies the risk.

 

On 18/03/2023 at 07:45, Dave Jones said:

if you have windows in that elevation for example you can get away with it.

Good point.. at the right time you can detail this.. you let the lintel slip at one end and put a small movement joint above.

 

 

2 hours ago, saveasteading said:

There is nothing magic about 6m

Now that has made me think.. You are right.. but both the English and Scottish regs are kind of giving rules of thumb, small building guidance... maybe also called deemed to comply.. if you do this and provided there is nothing "odd round about" it will be ok.. maybe..

 

In terms of the regs in this context a lot of them were written a long time ago.. call it tacit knowledge but also a lot of thought has been put into it.. by some clever folk.. and each reg has to be read in conjunction with all the others. They also get updated so let's take them as current.

 

My thoughts on the 6.0m thing is that beyond that you may get a lot of defection in say a joist / steel beam. That causes the end to rotate  more.. the guidance assumes a simple support at the joist / beam ends. The rotation introduces (springs to mind) two deterimental effects. The first is that it shifts the centroid of the bearing closer in span.. thus you get an eccentricity of loading on the wall.. introduces a bending moment which masonry is not ameniable to... it can significantly reduce the load bearing capacity of the wall.

 

The other one is that if you are using timber joists (if you could get them to span that far as you say) then you'll get concentrated load and crushing of the timber. Or if using steel you need to check for crushing at the inside face of the block.. well you don't as you design the steel beam to deflect no less than say span / 360 (12mm is a also good number... but not over glazing) so you reduce the beam end rotation and the problem goes away.

On 16/03/2023 at 20:35, Beanyboy2802 said:

Thank you for any help you can provide

Yes keep posting and loads of folk will chip in.. then you will be in the best place to make informed decisions as to how to spend your money.

 

 

 

 

 

 

 

 

 

[Beanyboy2802]

3 hours ago, Temp said:

+1 Perhaps run a steel across the other way so your timber joist span is halved.

I like the thought of this - but how would I implement it? 

Obviously I need a structural wall at each end of the steel beam, to support the beam, and hence the floor. Can the beam just sit into the structural wall as it is, or do I need to build out that wall to meet the beam (like a buttress)?

[Beanyboy2802]

58 minutes ago, Gus Potter said:

Fantastic.. it's great fun, sometimes frustrating but sounds like you are putting a lot of thought into it and reading up, reading around and expanding your knowledge. You'll reap the rewards of your efforts.

Yer, frustrating is right lol. I started the process blind, before having any knowledge of the building regs at all - but it had gone pretty smoothe while just working up a concept. 

Figuring out exactly what the wife wants was a challenge, seeing as she didn't really know herself (!), but we sort of get there. Keeping it to a reasonable plot size as well to be fair. 

But then when I looked at the regs - 70m^2 area limit inside any set of structural walls. Walls no greater than 12m. Adjoining walls not allowed doors at the end. Floor spans is just my latest crisis, and I've been at it for less than a week!

(On a side note, while it's in my head - I assume the ground floor doesn't need to worry about floor spans - it's on the ground..!?)

So far all these regs related issues have taken me longer to sort out than the rest of the house combined, and I feel like I'm only just scratching the surface. I've made a number of "compromises" already (some have resulted in design improvements, to be fair), and every change seems to be moving me away from my ideal outcome. For example - at present I have a 4m long storage cupboard in one of my bedrooms. I just don't know what else to do with the space, I can't move the structural wall without compromising elsewhere, or going over the 70m^2! 

it's a headache - but you're right, it will be worth it in the end. Hopefully..! 

[Gus Potter]

2 minutes ago, Beanyboy2802 said:

I like the thought of this - but how would I implement it? 

Obviously I need a structural wall at each end of the steel beam, to support the beam, and hence the floor. Can the beam just sit into the structural wall as it is, or do I need to build out that wall to meet the beam (like a buttress)?

I would love to chip in more but need more info to give a reasoned response.

 

You are right in that any vertical load bearing beam needs a structural support. You may not need the return masonry.. the buttress.

 

If you can post your rough scheme and let's see what comments that generates. Then we can look at the whole thing in the round.. we can all have fun helping you and that will hopefully give you the info you need to move onto the next stage.. better informed.

 

You'll get loads of info here on BH.. I learn new stuff all the time here.

 

 

[Gus Potter]

1 minute ago, Beanyboy2802 said:

Yer,

Posts have over lapped will read yours now.

[Beanyboy2802]

Just now, Gus Potter said:

I would love to chip in more but need more info to give a reasoned response.

 

You are right in that any vertical load bearing beam needs a structural support. You may not need the return masonry.. the buttress.

 

If you can post your rough scheme and let's see what comments that generates. Then we can look at the whole thing in the round.. we can all have fun helping you and that will hopefully give you the info you need to move onto the next stage.. better informed.

 

You'll get loads of info here on BH.. I learn new stuff all the time here.

 

As I say, any guidance is very much appreciated - and I'll get a (very rough) drawing uploaded when I get back to my laptop shortly - thank you! 

[Gus Potter]

1 minute ago, Beanyboy2802 said:

As I say, any guidance is very much appreciated

You'll get great help here on BH and support.

 

I'm an SE / Designer, do a lot of domestic stuff but can only really chip in a bit.

 

What I can say is that the breadth and depth of knowledge on BH is astounding, and it's right up to date in real time.

 

The great thing for me is that there are loads of folk just starting out and are working hard. One of the reasons I responded to you was that I felt that you have put a lot of effort into reading the regs and to get your design as far as you can.

 

If you do post your drawings and thoughts your big problem is going to be how you digest the feed back you get!

 

But if you can it will save you money and you may get something you may thought you can't afford at this stage.

 

 

[Beanyboy2802]

30 minutes ago, Gus Potter said:

You'll get great help here on BH and support.

 

I'm an SE / Designer, do a lot of domestic stuff but can only really chip in a bit.

 

What I can say is that the breadth and depth of knowledge on BH is astounding, and it's right up to date in real time.

 

The great thing for me is that there are loads of folk just starting out and are working hard. One of the reasons I responded to you was that I felt that you have put a lot of effort into reading the regs and to get your design as far as you can.

 

If you do post your drawings and thoughts your big problem is going to be how you digest the feed back you get!

 

But if you can it will save you money and you may get something you may thought you can't afford at this stage.

 

 

 

Like I said, any nugget of information can help and is really appreciated - it's why I'm here, and I'll try to contribute elsewhere if I can as well, to pay it forward. 

 

Attached my sketches as of right now. As I say, there have been a few compromises - and I don't know for sure if what I've done thus far is reasonable or anything. 

 

Few things to note, things I've compromised on;

1. The storage cupboard is huge - it was originally part of the dressing room, but the need to have the structural wall (and align it to the structural wall downstairs) just left Bedroom 2 too large to be reasonable. Hence, reduce the bedroom, make use of the "dead space" in some other way. 

2. I wanted integrated wardrobes in all rooms - but Bedroom 4, the structural wall requirements prevented my extending the shower into that room a little (through the wall) without a visible, so the alcove I had was removed. Not a major issue, but a little annoying. 

3. Not sure if the door to Bedroom 4 is compliant - could be too close to the end of the wall. I think it meets the requirements of Regs, Diagram 14, P5, but not sure if the 550mm in Diagram 12 applies at a wall corner. Genuinely don't know which is correct, but the wall of the bathroom prevents 550 working, so I've done the 350 not sure what I'll do if that's wrong. 

4. Speaking of the bathroom wall - it's already moved for the door, making the landing wider. The landing is also wider on the opposite side because of the position of the structural buttress (to align with where it could be placed downstairs). Not sure if it's, again, a poor use of space, having a landing that big - the rest of the house is big enough I think, but my thought is "Could it be smaller?" as a matter of efficiency more than anything else.

5. The main bathroom shower was turned into a bit of a "wet room" because of the structural changes. I don't mind this - but it took a bit of convincing (and a rough 3D sketch) to talk my wife around to the idea. Again, was made necessary by the structural wall changes I needed to make. 

6. Floor spans are a thing. I don't know if what I have is at all workable at this point, particularly in the master bedroom which has the biggest "unsupported" span between structural walls. Again, I'm assuming the downstairs will be fine just on the ground. 

 

There is probably more I could bring up - but I think that's enough to digest to start with. I think I need the dummys guide to building regulations to give me a head start! 

 

But that's my early design work, as it stands. Please, everyone - feel free to critique and advise as you see fit!

Extract.pdf