13k sqft self build in Hertfordshire

[LadybuilderLOL]

Hey guys 👋🏻

 

I am based in Hertfordshire and seeking mentors, new friends and friendly advice from any kind and willing soul with experience.

 

I bought a bungalow with the benefit of planning permission and certificate of lawful development to build a dream home.

 

Our self build has been designed as a reinforced concrete frame superstructure. With a subterranean basement and 1st floor.

 

I am reluctant to go back to the drawing board with a new design since a lot of design work has been completed and anyway, why mess with greatness? 

 

But... the astronomical estimated cost of the rc frame (the 1 quote I have received) has me seeking out quotes and suggestions on solutions to my 'budget' issue- there are of course many ways to skin a cat- I'm just unaware of the methods...

 

We have inherited some cgis from the seller: which you can see on my instagram: @londoner2landowner (trying to maintain a level of location privacy on the www)...

 

I have drawings which I own copyright of, the architectural drawings and the structural engineers drawings- in read only format at the moment (need to figure who owns the copyrights and agree a price 🙃) but may not be necessary to purchase if we go with a MMC.

 

I still need to hire an M and E contractor and and an interior designer. 
Which I have decided to do right from the start so that everything can be properly pre-planned into the drawings.

I have sent enquiries to around 15 ICF contractors and concrete framework contractors combined in respect of the super structure. 

 

Question 1: what contractors and method of concrete build did you use for your superstructure and why? 
Recommendations would be greatly appreciated. 
 
I watched an episode this morning where the self builders used pre cast concrete framework and what looks like a pre cast concrete basement. 
I have spoken today to a wonderful gentlemen at Glatthaar Keller.

 

Question 2: 
Can someone please tell me what will be the most economical way to build my house? 
ICF, pre cast framework or rc frame concrete pour?
Am I missing any other method? 

 

I don't know where to start so I've subscribed to build it mag 😆, since September 24 I've been to the Home building and renovation show, then I went to grand designs live, decorex international and the NSBRC 😥

I've booked to go on 2 courses at the NSBRC in February and March 35.

 

I'll be honest: ChatGPT is a great help: I have asked questions like: 
'Write me an invitation to tender on my new build project'
And
'List the packages that need to be priced on a new build house project'
And 
'What are the pros and cons of sips and ICF frame systems'

Try it 😆

 

I've probably left the most important details out of this post and waffled on. 

Please if you have any similar projects and are welcoming site visits, I'll bring coffee on my way to site 😀 I'm determined to make this a worthwhile learning experience and I will always welcome others to my site: I just need a plan first. 

 

For now, the bungalow is rented on a company let which gives me sometime to figure this all out.

 

If you got this far- thanks for reading. 

Kr,
J

Edited October 28 by LadybuilderLOL

[Jilly]

Wow, it looks like an ambitious project which you are tackling head on, well done!

You are right to be cautious, self build is a massive learning curve and it’s very easy to go way over budget.

 

Are you thinking of staying with the same architect for Building Control and construction drawings? You could maybe ask them to find cost savings? They will be familiar with, and invested in, the current design. 
 

Sorry I can’t help with the concrete question as I did block with cladding, and only a small project, but can offer moral support when you need it😊

Are you planning to project manage it yourself?  It might cramp your style to live in a static caravan on site, but it saves quite a lot in rent and means you are on hand for the inevitable questions which arise and early deliveries etc etc. 

@ToughButterCup has some hard won experience you can read about using ICF. 

Looking forward to hearing how you progress. 

[LadybuilderLOL]

Hi Jilly,

 

I welcome all moral support thank you 🤗

 

I have help on the PM side- a willing friend who helped us source this plot actually. 
 

It is ambitious and it's my desire to go down the pre fab route as much as possible. 

 

I am considering using the same architect- this is also cost dependent, however if I go down a pre fab route, I'm finding most contractors build the drawings into their costs. There are detail drawings available but they are based on rc frame concrete pour, icf has a different detail altogether...I think 🙃

 

We live off site and that won't change for now but I plan to be on site everyday regardless. 
 

 

 

 

[Thorfun]

Wow! That’s one heck of an ambitious project and a stunning design. I wish you all the best with it. 
 

looks like most of the building is built into the landscape so concrete really is the only way. The above ground bit could be timber frame if you wanted a change of materials. 
 

prefab concrete panels will be quick but expensive. Formwork and pouring concrete surrounded by EPS would be cheapest I imagine but will take longer. ICF might be comparable but you’d need to get quotes and SE drawings that are ICF specific afaik. 
 

checkout the basement forum as that’s pretty much what you’re building. There are many ways to do it and it all depends on what works for you and your budget. 

[JohnMo]

1 hour ago, LadybuilderLOL said:

But... the astronomical estimated cost

Nice looking place but not convinced by a number of things that seem strange.

 

Loads of bedrooms (2 floors worth) and limited living space in comparison. Not all those people housed in the bedrooms should want to crouch up on a couple of sofas.

 

But sorry that size build everything will all be astronomical. 1200m² is just huge it's 6x bigger than our very roomy 3 bed house.

 

1 hour ago, LadybuilderLOL said:

ChatGPT

Hope you proof read and facts everything, so you don't make yourself look a foolish. Chat bots make a good looking document that may or not be factually correct.

[LadybuilderLOL]

Thank you I'll check out the basement section.

Please share what appears strange to you?

 

I understand and am prepared for the costs of the build, but if there are more economical solutions I will always look into them.

 

 

 

[LadybuilderLOL]

The basement floor is designed as a car park currently and there is a 25 seat cinema that is too big. 
we will be seeking to redesign some of the spaces. 

[Jilly]

On such a large project you could consider doing it in two stages so that you could move in earlier (rather than the caravan option!)?

Loads to think about, but with lots of land you have plenty of options with aesthetics, screening planting etc. 

 

[Conor]

Hi. We built a three story ICF house with basement, but not on this scale.

 

 

(I'm a civil / environmental engineer, not structural, I'm sure our resident expert will comment in due course)

 

With the scale and design of this structure you might beyond the realms of normal building methods, and builders for sure. The best construction method will be determined largely by the structural requirements. Your basement walls will likely have to be shattered reinforced concrete as ICF blocks aren't ideal and most won't be wide enough, you are looking at 400mm+ thick walls here. I'm sure there are ICF projects similar to scale, you'd need to dig in to it. Same for you floor decks. These will be commercial building / car park type affairs at ~250mm thick with a bit of chunky steel holding them up. These kind of things, plus the excavation requirements, massively change the game, and costs. There is little economy of scale when you jump from a residential brick n block to a pseudonym commercial type construction. 

 

Not going to comment too much on the design, but things like you have an unfeasible amount of glass (apart from being uncomfortable, unlikely you'll pass SAP assessment), and cars are waterproof and don't mind the cold

10 hours ago, LadybuilderLOL said:

Iam reluctant to go back to the drawing board with a new design since a lot of design work has been completed and anyway, why mess with greatness? 

 

Cost wise, you say you are prepared, I'm assuming you know this will cost about £4m? It's never too late to change a design. A full redesign could cost you less than 5% of the construction cost, but could save you 30% or more.

 

I'd speak to an SE before you go anywhere, and another look at the design. You could shave off a £million and not lose any rooms /functionality for sure.

[Kelvin]

Why is it so big? Do you really need so many bedrooms? You could half the size (which would still be enormous) with a similar design. There’s a £2 million saving. Unless you really need a commercial sized building I’d seriously rethink the design especially as you are already baulking at some early estimates. 

[saveasteading]

3 hours ago, LadybuilderLOL said:

am prepared for the costs of the build

How exciting.

It is an office block Or hotel.

Few builders can do this so you need big, commercial builders. Add 50% to any general guidelines.

 

A 2 storey retaining wall is remarkable. Huge costs.

 

Also concrete is unforgiving. Where do insulation and services go?

 

My hunch is that steel, or hybrid, might be better value, but I would be costing it in several ways.

 

Presumably you don't have much external space, hence the 6 cars in the basement.  So lots of excavation and retaining walls,  and high muck away costs?

 

You need a lift. 

 

My hunch is to agree with the £4M plus VAT. Plus allow risk. 

I can't see anybody with £5M available living in a caravan for 2 years.

Edited October 29 by saveasteading

[torre]

Maybe you could improve the flow from entrance to living space. It's the first impression for guests and how you'll use the space every day.

 

Right now you come up the impressive outdoor steps, through a grand entrance way to... a lobby and a storage wall? Then turn 90 degrees and back 180 degrees up smaller stairs to the living space.

 

Instead think about pulling the lobby and stairs forward a bit so the stairs can continue running forwards up to the living space, so you're greeted with a more open space and invited in.

 

If you need a panic room, wouldn't you want direct access from the master suite on the right of your plans?

I agree with others if you've 9 bedrooms you need more living areas - how far do you want to be from a coffee machine! Also that it's very (very) large - easiest way to cut costs and simplify construction would be to make it smaller, but bear in mind almost everyone (me included) will be giving their perspective from experience on much smaller builds.

 

Good luck, I like the external design and how it fits the landscape.

 

 

[Indy]

This looks fantastic and I'm going to go the opposite direction and say why not build the space if you can afford to. Whether you need 13k+ sq feet is debatable but I'm all for space. 

 

The other points already raised also ring true - if you can afford to build a house of this house, then its unlikely you'll be living in a static caravan for 2 years especially with kids in tow. 

 

Also, I would want a specialist concrete builder doing the E2E project management on this rather than risk taking parts of it on yourself. Sounds like a lot of structural elements to consider and be done right. 

 

Following the thread with interest. 

[joth]

Welcome! Another Hertfordshire based self-builder here. I did a deep retrofit in Harpenden in the pandemic, and been helping with M&E and home controls for a number of friends on self builds since then - happy to have a chat on local options for this if you're nearby, feel free to DM me.

 

 

12 hours ago, JohnMo said:

Loads of bedrooms (2 floors worth)

1 hour ago, torre said:

I agree with others if you've 9 bedrooms you need more living areas - how far do you want to be from a coffee machine! Also that it's very (very) large - easiest way to cut costs and simplify construction would be to make it smaller, but bear in mind almost everyone (me included) will be giving their perspective from experience on much smaller builds.

 

 

If I am reading this correctly, from the elevations this is a 3 story build but includes plans for 4 floors - It looks like the first and third floor plans in the series are alternative options for the "middle" bedroom floor: one with w cavernous placeholder "storage util" room, and the other with it built out as a cinema and safe room. So in fact it's a slightly more modest 4-5 bed house?

 

 

 

[Kelvin]

2 hours ago, Indy said:

This looks fantastic and I'm going to go the opposite direction and say why not build the space if you can afford to. Whether you need 13k+ sq feet is debatable but I'm all for space. 

 

The other points already raised also ring true - if you can afford to build a house of this house, then its unlikely you'll be living in a static caravan for 2 years especially with kids in tow. 

 

Also, I would want a specialist concrete builder doing the E2E project management on this rather than risk taking parts of it on yourself. Sounds like a lot of structural elements to consider and be done right. 

 

Following the thread with interest. 

 

There’s space then there’s useable space. Our last house was twice as big as the one we built. The one we built feels bigger in part because we use all of it. I reckon we used 60% of the previous house at a push. There was one bathroom I never used once and was only in it a handful of times. 
 

I know someone that lived in a huge house. Not as big as this but still huge and a bit sprawling. It was terrific but he said they spent their life walking miles everyday as it was badly laid out until they eventually remodelled part of it to create a better living space with kitchen living room and a couple of bedrooms and an office. Almost a house within a house. All done to a high standard. He is a network consultant and placed activity monitors all round the house to track how they used it.  They found they rarely used the rest of the house.

 

To add it’s a stunning looking thing and more power to you for considering it. Our plot is on a similar slope and for a brief while we contemplated doing the same on a much smaller scale but similar idea. 

Edited October 29 by Kelvin

[Nick Laslett]

@LadybuilderLOL, welcome to the forum. Amazing looking project. There are a few Grand Design episodes with similar challenges. I binge watched my hours of that show once I started on this journey. I remember one where they used pre-cast concrete panels, which looked like a neat way to solve some problems. 
 

We have an ICF build in Suffolk, near Bury St Edmunds. We used Thermohouse, they supplied the materials and built the superstructure. Very happy for site visits if you are interested in finding out more about their products and our experiences. 
 

https://thermohouse.co.uk/self-build/

 

We visit Hertfordshire a lot, my wife is from Berkhamsted. We are still finishing the internals, but there is now light at the end of the tunnel. 
 

 

Edited October 29 by Nick Laslett

[Iceverge]

Welcome!

 

Wowzser! LA hills or Bond Villian mansion, I love it. 

 

The scale and complexity of it are going to drive up the cost. More or less everything you see about costs here will not apply sadly.

I was guessing £4million initially but on refelection I don't think I'm even close. Maybe £6m. Professional fees alone are lightly to be well into 6 figures. 

 

It'll be a commercial contractor for the project as it's too expansive for a domestic builder. However you're unlightly to get commercial discounts as it's a one off project and will require much better asthetic detailing than the equivilant warehouse or block of apartments. Don't be suprised if most refuse to quote or else come back very very expensive. 

 

 

On the practicalities I would say ICF alone is unlightly to be the best solution, or prefabricated concrete.  In LA or the 1960's it would have been an easier build as the thermal considerations would be far reduced. Steel frame and poured on site floors and roofs would have been the order of the day running right through from inside to outsde. 

 

However I think if you want a really warm and durable house there's going to have to be serious consideration given to how effectively completely decouple the external conctrete shell from the house interior whilst still retaining the continious feel on a monolithic design. 

 

 

I'm going to scratch my selfbuilder chin and think about it for a moment I think!

 

Good luck!. 

 

 

 

 

 

 

 

 

 

 

[Jilly]

Don’t be disheartened by all these comments!
 

It’s looking possible that the design was done to capture the imagination to gain planning permission and a significant uplift in land value, but might not have been intended to be built as there was no budget. 

 

Self build is often a once in a lifetime thing, so most of us have a personal wish list which is modified by costs or family constraints. 

 

People very often submit new plans after purchase, safe in the knowledge that something will be passed. You enter the game of planning permission with more certainty.

 

I laughed to read the comment about not living in a static, but it’s not unheard of for Grand Designers to go bust/divorce etc so it’s important to be realistic. 
 

Many of us on BH have saved £1000’s with the advice and pointers given. 

[Kelvin]

As far as finding someone to do it. They do exist especially in the SE. There are specialist builders out there who do builds on such a grand scale. Who builds the houses for the rich and famous after all. I’m sure there was a TV programme about a builder who only worked on high end large scale builds. The CEO of the company I worked for had an extension built that effectively added a kitchen and dining area plus landscaping. Cost £1.5 million. 

 

A friend was telling me about an Edinburgh town house that was being renovated top to bottom and they were flying in the best people for each stage from around the World! 

[Thorfun]

+1 to considering getting new plans drawn up and resubmitting planning. that way you get exactly what you want not what the seller of the plot used to get through planning.

 

yes, it'll add 6 - 12 months to your schedule but think it'll be worth it.

 

Also +1 to the number of bedrooms. unless you need them that is. we have 2 kids and built a 3 bedroom house with big bedrooms. yes we could've fitted 5 bedrooms in the same space but didn't want to end up with pokey bedrooms with 2 spare rooms that would rarely be used.

 

obviously with a house your size these things aren't so important i guess but i'd rather my kids had space to enable them to stay well in to adulthood if required so there was space for them and partners.

[miike]

What is the sqm of the actual living areas? Looks to me like <50% of the 13k sqft is actual living space, with the rest as garages/courtyards/terraces. If I'm correct, then I think it could be built for a lot less than some of the above estimates. 

 

I recently built a not entirely dissimilar 3 storey house on a sloped site with 500m2 internal space + ~200m2 of terraces. The semi-submerged basement used two skins of blockwork, with a concrete filled cavity. The upper two floors were built with brick/block. There's about 75 structural steel beams. 

 

I would suggest looking at this method of construction rather than other more specialist types. I'd then approach groundworks companies and only provide limited drawings and ask to quote for specific sections - eg. the excavation, slab and blockwork for the basement floor. If you send all these drawings over then you'll probably get 50% added on to the price as they'll assume you can afford it based on the design.

 

Excluding windows, I'd expect c£1m for building the shell of this house. You should budget for a lift though if you're going to have parking on the basement floor and the kitchen two floors above - it's quite a journey when bringing in grocery shopping. 

 

 

[twice round the block]

Great plot 

Bad design. 

 

I would hire in another architect and do a design that works for your family. 

 

Art Deco on the side of a hill could look spectacular.

You may go through a couple of architects until you get one that really understands what is needed on the site that fit's your, "must have list and it would be nice if"

 

Unfortunately some architects just don't get it and see it.

There are plenty of good ones to choose from in the area that are RIBA affiliated.

Even when you get one that works with you; you may have too reign them back in as they can get carried away.

 

[saveasteading]

2 hours ago, miike said:

it's quite a journey when bringing in grocery shopping. 

And a legal requirement. I'm rather shocked that the architect (A?) doesn't know this.

[JohnMo]

12 minutes ago, saveasteading said:

And a legal requirement. I'm rather shocked that the architect (A?) doesn't know this.

Disability access is missing from the design altogether. No toilet facilities either on ground floor, in fact unless I am missing something a guest has to go into some ones bedroom, to nip to the loo. Quite a bit to sort really to get through planning.

[Indy]

The initial post indicates that it already has planning so I'm sure these things would have been considered already?