Having trouble comparing quotes and understanding whats reasonable

[vab89]

10 hours ago, saveasteading said:

But...as a rule of thumb I say that a single storey building costs the same, per useful m2, as 2 storey.

 

This doesn't apply for a very small area though, as the stair takes up so much space. on one or both floors depending on arrangement.

Miss out the stair and mezz, save 1/4 of your cost, and lose ...not an awful lot of floor.

This means nothing of course if it doesn't provide the accommodation you want.

 

tbh fine with 1 storey, just thought that design-wise it might have been easier to get through with 2 storey as same look as house. but at same time even croydons own guidance document 

https://www.croydon.gov.uk/sites/default/files/2022-01/spd2-suburban-design-guide-chapter-4-residential-extensions-and-alterations.pdf

appears to show pictures of lots of awful designs that appear to have been approved (or atleast built :D) 

the other reason was that the logic was that with 2 storeys less need to expand side ways. but again, 2 storey/mezzanine not a hill to die on.   

 

4 hours ago, BadgerBadger said:

 

It's a bit more specialist than a standard tree surgeon you might find in the yellow pages, try googling a arboculturist tree survey to get along the right lines.

 

You will need a tree survey for planning, it was one of the first things we got before starting design, so could look at getting it done now so the arboculturist can properly advise you.  The circular RPA is a good starting point, but there is some variation, and the presence of your garage foundation will have influenced it.  I'm going to guess the garage was built on the edge of the 12x diameter circle in the 1990s, and the tree has continued to grow since.

 

Either way, I think you're in for an easier ride to try and stick with the existing garage footprint as expanding further sideways into the RPA is going to be tricky.

 

This could be a good thing to quiz your architects to help you decide as it's going to be a big theme of any design/application.

 

thank you for guiding on the terminology. so jut to confirm then this arboriculturist survey can be leveraged & used in the planning process either way? we wouldnt need to do any subsequent other tree surveys? it kind of seems like as soon as the architechts heard me mention the TPO tree (and one saw it in person & granted mentioned it might have been a problem) should have said "first step, before you hire us, do a arboriculturist survey first to understand if this is possible", am i right? 

 

& yes you are probably right, it must have been sooo much smaller back in 1990s. see below pic 

 

 

i couldnt measure it exactly due to access issues but id say its atleast 1.5m diameter and def within 12x1.5m of the main house, let alone the garage. for reference those tiles are c60cm. the garage footprint is c.2.6-2.7m so we would need to expand atleast 60-1.2m ideally sideways if 1 storey. there is a manhole cover close to where those yellow hoses are so cant really go sideways and backwards...but thankfully 1-2m can go forward before getting to edge of front of house

 

3 hours ago, Kelvin said:

It seems a big expense for a relatively small space. 

 

you talking about all in option 1 & 2? yes i tend to agree. although the architectural design quotes seem roughly OK? option 3 said 1 storey would be c400-500 cheaper (so 1.2k+VAT)

 

1 hour ago, Marvin said:

Hi @vab89

 

I have done a bit of digging....

 

My way of approaching your plan would be to check out the following personally before getting involved with Architects and builders.

 

The major obstacles of concern for me would be:

 

Planning: When I have been involved with extensions involving a separate access they were denied and access had to come via the main front door....!! 

 

Conservation rules: What are they? I think you will need planning permission. Check for an Article 4 Direction (A4D) which is part of planning legislation that allows the council to remove permitted development rights including changes of use from an area or a particular property in certain limited situations where it is necessary to protect local amenity or the well being of an area.

 

Look at web site, link below, and scroll down to the bit titled: Do I need planning permission to carry outworks to a house in a conservation area?

 

https://urbanistarchitecture.co.uk/how-to-get-planning-permission-in-conservation-areas-in-london-and-the-uk/#:~:text=Basic single-storey rear extensions,build one under planning permission.

 

Check previous planning applications in your area: A similar application was permitted in your area, however no front door and no second story: Use this reference

 

 

https://publicaccess3.croydon.gov.uk/online-applications/   

 

 

TPO: As others have said if you need to do works near a tree with a TPO, be it access requirements or foundations or drainage, this can be expensive.  With limited knowledge of your home and grounds I would make the assumption that piling would be the only way forward IF a change to the existing foundations were required. However access and space for the equipment become a challenge...

 

 

Drainage: Where does the rain water go? Sewer? soakaway?  Will the work involve digging more holes in the ground??

 

I'm only being Mr negative to try and save you money.

 

Good luck

 

Marvin

 

 

 

 

 

 

thank you for detailed response. is that even the case when the extension clearly couldnt be registered as a seperate unit (ie no seperate utilities, no seperate address, below req. meterage?) could this be solved by front porch extension which then has entrance to both main home and to the extension? apologies for the childish looking sketch but just did this in 30 seconds to illustrate what i mean. sadly because our entrance is in the middle it might mean quite a big "wrap around porch extension / side extension" kind of approach versus home designs where entrance is at the side....tbh all architects told me that a separate entrance might be an issue but the approach to take is simply to have internal entrance then simply add a separate one later after all planning granted and go for change of design (i think) or simply not mention it....and if needed close over the internal one. for us it would be our utilitiy room where the wall adjoining the garage has some wardrobes...so technically thats what the door would be behind...

 

 

i checked and i believe the only article 4 restriction was no HMO. 

 

regarding the drainage etc questions - is this something that a builder would be able to answer at the same time they do the hole digging to investigate the suitability of the existing foundation (assuming the arboriculturist tree survey says shouldnt be an issue)?  many thanks for all the detailed suggestions! nothing wrong with being mr negative. i am mr negative too usually  nothing more negative than wasting 5-6k unnecessarily. 

 

1 hour ago, saveasteading said:

1. Expensive for a small building.

Would create a potential stress point between old and new, as the existing building will continue to move and the new one won't.

 

2.For all that I have my doubts about them, steel screw piles to similar depth as the existing founds might work.

 

3. Sometimes you have to accept that an idea is not feasible.

 

  

20 minutes ago, ETC said:

Use the garage as a base and build up to create the second floor. If you don't want a new postal number then it will be an extension rather than a granny flat. The planners may query the use and might worry that you are creating a separate dwelling but if you explain that it is an extension to your home with a connecting door to house a family member independently they should be OK. It can get messy if they think you are trying to create another dwelling.

 

would the garage (and foundation) have likely been created in a way that it would be able to support a second floor on top? part of the problem is on its own footprint the area is probably a tad too small. id need to remeasure it with someones help but i think externally its like 2.7x4x (maybe 5 at most)...i want to say its maybe 12sqm internally..and currently has the boiler and pipes either way which we want to move so i think the only option would be to knock down and build in its place. but yes 100% no need for new post address. mention it in this reply above but yes most architects suggested putting connecting door internally in schematics and planning approval and then just either adding external door after the fact or try get a subsequent additional planning change as well (perhaps approach it from POV of "when were away we dont want to have whole house be opened for use for safety reasons etc hence the seperate entrance"). 

 

again thank you everyone for all your replies & inputs! 

 

[saveasteading]

41 minutes ago, vab89 said:

must have been sooo much smaller back in 1990s. 

Foundation designs are based on tree distance and type,  but at the mature height, not the height at the time of construction.

More likely was ignorance of this at the time, because tree problems have increased more recently.

I've met bcos who knew nothing about the subject.

 

The tpo however is all about the health and significance of the tree. Building over or cutting a large proportion of roots will damage it significantly.

Also, building near a tree can cause it to readjust asymmetrically and just look bad.

 

 

 

 

 

[Bozza]

@vab89 I have messaged you a copy of my tree report for my planning application.  It will give you an idea of what the issues are & what a tree report involves and recommends etc.  I have 26 mature trees but no TPOs, I had to build around, but the principles are effectively the same.  
 

There is a bit of a chicken and egg here for you.  The tree report comments on the implications of a proposed build on the trees, but you don’t know what to build until you have an idea until an expert has guided you.  For me it was quite simple.  We marked the tree RPAs on our site plan then progressed our plan to build accordingly.

 

I think local authorities have someone who looks after TPO trees. Probsbly environment dept. If I were you’d I’d reach out to them with a general approach of I’m thinking about extending but don’t want to do any harm to the tree.  I love that tree.  I don’t want it harmed. Etc.  Can you give me a steer?   My application sailed through because I made sure I wasn’t placing any opportunities for the various consultees (including environmental) to make negative comments.   
 

Something sticks in my mind that up to 10% of a tree root can be disturbed without detriment but I don’t know about a TPO tree and definitely don’t take that as gospel.

 

before you do any further research on building methods designs etc I’d definitely do the research on the TPO tree.

 

Trees and bats have rights

 

 

 

 

Edited December 21, 2023 by Bozza

[saveasteading]

1 hour ago, Bozza said:

up to 10% of a tree root can be disturbed 

I think that's about right, but not if these 10% are critical for water or nutrition.

An arbori.etc once forecast to me that spreading earth over 30% would certainly kill them.

 

However I've seen our Borough approve new houses right underneath (3m at construction) oak trees, in an aonb. The housing target trumped the tree's community / ecological value.

 

The house will suffer too, with moss and mould, and blocked gutters.

 

[vab89]

1 hour ago, Bozza said:

@vab89 I have messaged you a copy of my tree report for my planning application.  It will give you an idea of what the issues are & what a tree report involves and recommends etc.  I have 26 mature trees but no TPOs, I had to build around, but the principles are effectively the same.  
 

There is a bit of a chicken and egg here for you.  The tree report comments on the implications of a proposed build on the trees, but you don’t know what to build until you have an idea until an expert has guided you.  For me it was quite simple.  We marked the tree RPAs on our site plan then progressed our plan to build accordingly.

 

I think local authorities have someone who looks after TPO trees. Probsbly environment dept. If I were you’d I’d reach out to them with a general approach of I’m thinking about extending but don’t want to do any harm to the tree.  I love that tree.  I don’t want it harmed. Etc.  Can you give me a steer?   My application sailed through because I made sure I wasn’t placing any opportunities for the various consultees (including environmental) to make negative comments.   
 

Something sticks in my mind that up to 10% of a tree root can be disturbed without detriment but I don’t know about a TPO tree and definitely don’t take that as gospel.

 

before you do any further research on building methods designs etc I’d definitely do the research on the TPO tree.

 

Trees and bats have rights

 

 

 

 

 

thank you very much. very helpful. is it of concern that architects didnt immediately guide me to this approach? option 3 did mention it but he seemed convinced it would be fine but that we would just engage a tree survey to show council why its not too big of an issue. 

[Bozza]

9 minutes ago, vab89 said:

 

thank you very much. very helpful. is it of concern that architects didnt immediately guide me to this approach? option 3 did mention it but he seemed convinced it would be fine but that we would just engage a tree survey to show council why its not too big of an issue. 

Three possibilities of varying likelihood assuming they were aware of big TPO tree encroaching on your site.

 

1.  Architect has a lot of experience on building near roots of TPOs/trees, and knows what he/she is on about.  And is right and you’ll have a trouble free project involving digging into the RPA of TPO trees because your local authority is ok with that. 

2. Architect has not a lot of experience with trees in that regard and genuinely doesn’t know it could be an issue,

3. Architect knows is could be a big problem but didn’t want to discourage you from paying for their services to them to the point where an application is refused. 
 

Thing about trying to speak with, if you can, the TPO / environmental officer etc at the council (for free) from the outset is they are paid the same regardless whether you submit an application, or not.   They do not decide whether an application is approved or not but in your scenario I think they could have a very crucial input as they are effectively an advocate for the tree.  In my case it was them who told mr about how to calculate RPAs and basically the more RPA and mitigations I do the greater the chance of a successful application.    So we designed a house / plot layout that missed most the RPAs, but meant taking down two trees.  No dig driveway etc.  so that resulted in the tree report that I sent you that was non controversial.  

[saveasteading]

Maybe I've missed it but let's  resolve the structural side of this tree thing. 3 questions.

What kind of tree is it?

How far is it from the tree to the closest point of the proposed extension? +/- 300mm for now.

What kind of ground do you have?  In your own terms....clay/silt/sandy?

[vab89]

On 21/12/2023 at 16:44, saveasteading said:

Maybe I've missed it but let's  resolve the structural side of this tree thing. 3 questions.

What kind of tree is it?

How far is it from the tree to the closest point of the proposed extension? +/- 300mm for now.

What kind of ground do you have?  In your own terms....clay/silt/sandy?

 

thank you for your reply. apologies for the late response - got caught up in the festive period. hope everyone had a lovely christmas!

 

It is a lime tree. measured today and circumference is c.270cm so diameter should be roughly 86cm. 

The garage is currently 2.6m x 5.4m and the closest point to tree is 3m away exactly. we would increase the width by 90-120cm if possible

Clay ground

 

Ive attached some more images showing the front and back of the garage (note the tials are 60cm for reference). the distance from garage to edge of house is 2.3m. based on this then i think the maximum length is around 7m (60cm backwards and 2m forward - although it would mean either making the meter readers internal or moving them) and then however much we can extend sideways from current 2.6m (so perhaps 3.8m? ie 2 tiles). this would mean moving our current shed and a pretty small space for entrance next to tree...giving a grand total of  around 26.6 footprint (and smaller internal space).

 

so perhaps just under the desired size. really it does seem that a two floor would probably be much better choice size wise i suppose the question is it seems would the roots present an issue to the foundation needed for this

 

if perhaps a front wrap around porch extension is not a feasible idea then perhaps the entrance can come from a small conservatory extension which can serve as the entrance into the side extension? ie grandma would need to enter via side gate, walk down garden and enter via conservatory? this way still connected to main house so shouldnt cause issues?

 

Edited December 28, 2023 by vab89

[saveasteading]

4 hours ago, vab89 said:

It is a lime tree. measured today and circumference is c.270cm so diameter should be roughly 86cm. 

The garage is currently 2.6m x 5.4m and the closest point to tree is 3m away exactly. we would increase the width by 90-120cm if possible

Clay ground

 

OK.

A lime tree will grow to 22m and is classified as having moderate water demand.  The current height, and the diameter are not used in the assessment.

Clay has high shrinkage.

so  look on this table 

 

 

 

and we see that at 3m from the  22m high tree, the   depth  of foundation required is 2.15m 

 

 

[vab89]

21 minutes ago, saveasteading said:

 

OK.

A lime tree will grow to 22m and is classified as having moderate water demand.  The current height, and the diameter are not used in the assessment.

Clay has high shrinkage.

so  look on this table 

 

 

 

and we see that at 3m from the  22m high tree, the   depth  of foundation required is 2.15m 

 

 

 

thank you for your reply. i assume that a 2.15m depth foundation requirement is prohibitively expensive? if we want to get wider e.g. 1m away then foundation needs to be 2.35m....what does this info mean for a potential cost estimate?  +10-20k? or basically, renders this whole plan so moot that theres not even a point in inviting arboriculturist? will planning simply reject anything less than 2.35m foundation? 

many thanks for replying with these details!

[saveasteading]

Planning don't do technical stuff like that. However they might dislke the effect on the tree, because it would grow mis-shapenly and drape over the house.

Also from your maintenance point of view it will tip leaves onto your roof and gutters.

If you can get a decent digger in, then its just a trench and concrete. More concrete than if it was shallower. £120/m3 or so, plus the extra labour.

and the earth away cost.

So it is adding 5% to your build cost, or so.

 

 

[vab89]

3 hours ago, saveasteading said:

Planning don't do technical stuff like that. However they might dislke the effect on the tree, because it would grow mis-shapenly and drape over the house.

Also from your maintenance point of view it will tip leaves onto your roof and gutters.

If you can get a decent digger in, then its just a trench and concrete. More concrete than if it was shallower. £120/m3 or so, plus the extra labour.

and the earth away cost.

So it is adding 5% to your build cost, or so.

 

 

 

thanks for your reply. so based on this, in your opinion, does it sound like it still makes sense to organize the arboriculturist visit & report followed by a builder visit with a high-level cost estimate to give us an idea and then start with the planning consultant?

 

had a quick (very) google and it seems that 2m-3m should be expected either way for a 2-storey extension foundation...so suppose the only thing is that we wouldnt be saving money on foundation by going 1 storey only due to presence of the tree...HOWEVER it does potentially mean that we could do a 1 storey extension for now and have the foundation be proof for a future 2nd storey extension on top potentially further down the line? 

 

suppose its more structural engineer job to advise on foundations but i assume builder should have some idea too about options available in such scenario? 

 

many thanks again

[saveasteading]

15 minutes ago, vab89 said:

2m-3m should be expected either way for a 2-storey extension foundation..

No. the extra load from the upper storeys does perhaps add to the width of the footing. 

if the ground was weak nearer the surface and stronger lower down then that might be anther reason.

but about 1.4m is the norm.

17 minutes ago, vab89 said:

builder should have some idea too

a very sweeping assumption.  probably not.

 

id say add £4,000 for being near the tree.

 

BUT there are other issues too, so get specific advice. 

eg. is it wise to build an extension footing at 2.2m if the house's is at 1,4m, or whatever.

[vab89]

so i got in touch with the council development officer who pointed me to tree officer who recommended a local tree consultant who said following once i explained what i wanted and showed the pic:

"It would be too close. Not only would it result in an excessive RPA incursion, but it would also be within the structural root zone, which is a no-no.

The only feasible looking option would be to remove the tree, to facilitate the development. Is it protected?" 

 

i replied its TPO. still waiting on response but based on this it seems extension is a no go :(