Zoot's Extension- advice needed.

[zoothorn]

@PeterW hi- ok understood Peter, in retrospect re. the float idea, to get this + a lesser structure below it later by myself.. surley be more problematic & likely not £save over orig idea. A line thru this idea then.

 

When you say a "single" TF structure.. what do you mean, single story/ single course?

 

Ok final plans thus (my cam used from pdf images, 11/ '17!). Its the LHS section of house. The lower room2 'box' is set -down- a foot, in order to get max internal H in room1. A knock-thru door into room1 from adjacent main house bedroom. Room1 = proper room, room2 = basic workspace.

 

 

[zoothorn]

On 19/05/2019 at 15:20, Tennentslager said:

Dig trench

part fill with concrete and maybe rebar

brickie builds block work to appropriate level

inner leaf for timber frame and depending on look/style outer leaf for brick work

make all nice and flat inside

cover in visqueen and more concrete poured inside 

timber wall plate attached to inner block work and timber frame onto that

 

that is one simple way to describe a straightforward extension with no drainage or other works underneath 

does that help?

 

Yes helps alot thanks Tennents'. Where does the floor insulation fit in to the mix tho? I thought there was 100mm as standard thesedays, & it was within this 1st phase, prior to main builder coming along ontop of floor to build walls.

 

I'm reading suggested Haynes: Home Extention book now, 1/3rd way thru. JesusH I thought it was difficult to understand before.. now Ive got another ton of things more to consider (I honestly have no comprehension how anyone could contemplate getting an extention made, let alone actually going ahead, its so complex I'm snowed under trying to understand the processes & totally up a gumtree.. but I have no choice but continue).

[zoothorn]

Can someone help me out on this simple Q. If an inner course wall is built, say a TFrame, & I'm left to 'choose any manner of ways to clad the outside'..

 

Does a cavity -always- have to be incorporated between the two courses? and if I choose a nice stepped-vertical-cedar "cladding" for my outside.. what does it fix onto? I mean if there's a cavity (& I think its right that a modern wall has to have one) it can't be fixed it to the inner course. So what does it fix onto.. I can't  visualise/ understand it. I can understand perfectly, if the outer course was block, or, if the inner course was block & the cladding fixed to this with no cavity between.

[Tennentslager]

Not that I’m any expert but you could have a single row of blocks and 145mm thick timbers to make the walls with OSB sheet on the outside then your vapour barrier on top of that

batten this both horizontally and vertically and attach you cladding to the battens.

this will create a rain screen and the battens create a cavity behind this for air movement 

insulation goes in between the 145mm timbers with plasterboard inside...

@Peter and @Declan52 will tell you if I’m talking mince

[zoothorn]

Hi Tennents'. Thanks I understand what you say.. but I'm now more confused as a result, bc I was sure, that a cavity of maybe 50mm(or thereabouts) HAD to be between TWO wall courses.. for an extention/ for any modern dwellings' wall construction.

 

When you say 'block & 145mm timbers'.. are you talking about both with the construction of one course, or a block & timber ie two separate courses?

 

Or to put my Q another way. What are the options of wall construction for my extention? I mean forget the complicated options: what are the more simple types I could consider to meet BCO standards, but of course be solid still-?

[Declan52]

Ok I'm a bit lost and I have read this post 3 times. What is the wall build up your going to use.

Option 1. Timber frame with cladding on the outside

Option 2. Timber frame with block, plastered or clad

Option 3 block and block

You need to pick a route then we can advise the best method of doing that particular type of build.

[zoothorn]

Hi Declan. I have not decided on the wall build- I need to know the options, in order to be able to choose (this is typical of the series of catch22's I seem to be stuck firm in last few months).

 

If I'm considering timber frame, and I understand now the basics of this construction as primarily its all to do with a TF inner course, with say bricks or blocks as "cladding" options.. I'm 1st trying to understand whether a cavity is needed in such a wall. Then, if so, I'm trying to understand how a wood cladding (not brick cladding) attatches to this cavity (it can't is my point- it can't attatch to thin air, so what does it attatch to?).

[PeterW]

9 minutes ago, zoothorn said:

Then, if so, I'm trying to understand how a wood cladding (not brick cladding) attatches to this cavity (it can't is my point- it can't attatch to thin air, so what does it attatch to?).

 

The answer to this, is this ... 

 

1 hour ago, Tennentslager said:

and 145mm thick timbers to make the walls with OSB sheet on the outside then your vapour barrier on top of that

batten this both horizontally and vertically and attach you cladding to the battens.

this will create a rain screen and the battens create a cavity behind this for air movement 

 

From the inside:

 

plasterboard

batten

vapor control layer (plastic sheet)

145mm timbers packed with insulation

OSB

breather membrane 

vertical batten

horizontal batten

render board

render

 

Make sense now .??

[PeterW]

@zoothorn if you want to change to cladding rather than render you would need to go back to planning. 

 

Whats your  budget for this ..??

 

 

[zoothorn]

13 minutes ago, PeterW said:

 

The answer to this, is this ... 

 

 

From the inside:

 

plasterboard

batten

vapor control layer (plastic sheet)

145mm timbers packed with insulation

OSB

breather membrane 

vertical batten

horizontal batten

render board

render

 

Make sense now .??

 

More sense, thanks.. but where is the 50mm cavity tho?? I hadn't heard of a render board I must say

 

I thought all modern walls had to be 2 courses, with a cavity between, as a certainty.

[PeterW]

1 minute ago, zoothorn said:

More sense, thanks.. but where is the 50mm cavity tho?? I hadn't heard of a render board I must say

 

I thought all modern walls had to be 2 courses, with a cavity between, as a certainty.

 

Cavity is here :

 

17 minutes ago, PeterW said:

vertical batten

horizontal batten

 

2 x 50x25 battens at 90 degrees to each other and you have a 50mm cavity. 

 

You don't need a cavity anyway so not sure where you get that from. If it’s from a book, then it’s making general statements that aren’t correct unless it covers each build method.  

[zoothorn]

9 minutes ago, PeterW said:

@zoothorn if you want to change to cladding rather than render you would need to go back to planning. 

 

Whats your  budget for this ..??

 

 

 Chrissakes. I can barely cope with choosing & understanding what the heck the walls might be made from.. let alone the 'rules' processes.

 

Why the heck there isn't anything out there, like a simplified 10-step plan/ anything, to help normal folks comprehend the processes, I cannot begin to understand.

[Onoff]

16 minutes ago, PeterW said:

 

The answer to this, is this ... 

 

 

From the inside:

 

plasterboard

batten

vapor control layer (plastic sheet)

145mm timbers packed with insulation

OSB

breather membrane 

vertical batten

horizontal batten

render board

render

 

Make sense now .??

 

That build up for 2 storey?

 

Can you do him a drawing? 

 

 

[zoothorn]

2 minutes ago, PeterW said:

 

Cavity is here :

 

 

2 x 50x25 battens at 90 degrees to each other and you have a 50mm cavity. 

 

You don't need a cavity anyway so not sure where you get that from. If it’s from a book, then it’s making general statements that aren’t correct unless it covers each build method.  

 

I don't need a cavity? so what do I need then? how is anyone like me possibly in a position to choose what kind of wall construction to go with? or do I just say 'right, no cavity- so then I want a single block wall'. simple as that. can I do that?

[PeterW]

Just now, zoothorn said:

 

I don't need a cavity? so what do I need then? how is anyone like me possibly in a position to choose what kind of wall construction to go with? or do I just say 'right, no cavity- so then I want a single block wall'. simple as that. can I do that?

 

No ...! Not you... 

 

Read my post carefully. It is not a requirement to have a cavity, as in every construction must have one. There are build methods that mean you don’t need them , such as ICF, and even some timber frames use direct clad such as how @ProDave has done his. 

 

You could build a single block skin and then clad it with External Wall Insulation (EWI) and render that - perfectly legal to do  so long as you meet building regs insulation levels. Not sure how easy or cheap it would be to do. 

 

Go back to my question though, what’s your budget as that could dictate the method. 

[zoothorn]

7 minutes ago, PeterW said:

 

Cavity is here :

 

 

2 x 50x25 battens at 90 degrees to each other and you have a 50mm cavity. 

 

You don't need a cavity anyway so not sure where you get that from. If it’s from a book, then it’s making general statements that aren’t correct unless it covers each build method.  

 

But in my world, that's not a cavity bc its got wood in it- the moisture would travel across the cavity via the wood!

 

Ok I need to take stock & go back a step. Right, I'm reading all about walls' construction in the haynes book. And it has seemingly 2 options: block > cavity > brick... and TF > ? > cladding. I cannot figure out this ? bit, and, I want to know if these 2 options are the only ones.. or if there are others I can choose (or, has my choice been made already by way of the plans submitted & agreed by the PP?).

 

 

lordy.

[zoothorn]

@PeterW ok thanks. I must say this is amazing to learn I don't neccessarily need a cavity. You see I've worked on such a build (17yr old), witnessed such builds as a single story extension ~10 yrs ago, see only eg's of such builds around, & my plans submitted suggest this build either has, or will have, such cavity-based builds. So you see I had no other idea, than this was what regs stipulate for extention walls for a decade+ now.

 

Ok I need to reasses I think with this knowledge.

 

My budget is £30k with vat included.

 

My rough idea was to do as £best I possibly could: get builder to do main stuff: TF inner course 3x walls, floor, 2nd story, roof, 2 windows/ 2 doors.. all up to watertight. Then I do the outer course either myself (wood cladding all I could do, I'd think) or get s'one else cheaper to do. I pB inside. I do wiring. I finish off skirting, decorate etc.

 

If all walls are TF plus timber cladding, I'm worried about one thing: structural solidity. I get hit with full force weather at this spot- its sits like a duck in this respect. So if I -could- I'd be much happier with a BLOCK inner course instead.

Edited May 27, 2019 by zoothorn

[PeterW]

You could do that for change of £20k. 

[zoothorn]

That's very encouraging PeterW. (you could do that.. you mean me do it tho?)

[PeterW]

What I mean is that there isn’t that much to do, and whatever route you go, £20k should see you done and finished. 

 

Is the space below ie the ground floor room, part of the house or an unheated workshop ..? May make a difference for BRegs. 

 

Whats the actual purpose of the extension..? 

[zoothorn]

Unheated workshop exactly Peter, one door only.. but called a 'storeroom' (dont want regs to know a portion of my work done in here- no need to know).

 

Upper story really to make very best use of area above (& a very fine south view from french windows): this room yes part of house, via a knock-thru door from my bedroom. A 'study' its called, but a 3rd bedroom best 'sold' as.

[PeterW]

So it’s a workshop ..? Do you need it to be heated ..?

 

This does make stuff slightly easier but also complicated in other ways ..! You will need to insulate the walls but tbh you could get away with just full filling the walls with Rockwool, and the same with the floor of the room above. Then clad with celotex and you’re probably reducing the heat loss a lot. 

 

If  it’s an unheated space then still consider some insulation in the concrete floor but you can reduce it. This is purely down to comfort. 

[zoothorn]

No, I don't need it to be heated (only 10 hrs per week in it too, all 30 min bursts). The work tho will be routing: noisey & I'm close to road, so I have in mind ideally some wall density plus rockwool for room1 to appease sod n'bors complaining to authorities. A thick door is my idea too.

 

I thought regs would just enforce me to put 100mm insulation in the floor, even it called a 'storeroom' on plans.. but if it -saves a good chunk- & helps height without I'd be fine: if you might recall my mainroom ceiling is terribly low.. & replicating same ceiling H across in this "wing" means a ceiling barely 6" above my head- in a small room it'll be oppressive (main room's big). So idea is build a foot down.

 

thanks, zoot

[PeterW]

Thick door may not help that much but a lobby door would if you could move it so you had 2 doors at right angles. 

 

Got a dimensioned floor plan ..?

 

[zoothorn]

On 27/05/2019 at 21:50, PeterW said:

Thick door may not help that much but a lobby door would if you could move it so you had 2 doors at right angles. 

 

Got a dimensioned floor plan ..?

 

 

 

Yes below.

 

Tbh the door I can fashion it thicker, redo it even in time if very ''leaky".. or make a sliding panel across the door, inside, to baffle the noise maybe even. I can cross this bridge later/ last etc.

 

 

 

 

 

 

Edited May 29, 2019 by zoothorn