Hello - Architect turned self builder, building a new house in Hampshire

[SarahHutch]

Hello,

 

I am Sarah an architect turned self builder in Hampshire. Having worked for the last 15 years designing new large scale new housing developments in London, I am now turning my hand to building our family home on the site of an old bungalow.

 

We have been living in the bungalow since 2022 and have a planning consent for a renovation project. However after much consideration we have decided to go for a knock down and rebuild, to ensure that we can complete the project to high performance specification, whilst reclaiming the VAT. We have submitted a new planning application and are awaiting the outcome of that.

 

We are seeking to build a two storey house, from timber frame (from Kithurst Homes) with a insulated raft foundation (Kore/Greenraft or similar). The house will be rendered in lime render with a clay tile roof. We are keen to use natural building materials wherever possible, and whilst we are not seeking passivehaus certification we are following passivehaus principals wherever possible. Ie. high levels of insulation and airtightness, MVHR, PVs etc.

 

We would love to hear from fellow southern self builders, as whilst we are familiar with the design process, we have limited contacts with local builders etc. so any recommendations would be greatly received. I intent to project manage the build myself and am happy to get involved with some DIY, but currently have limited skills in that department!

[Jilly]

Welcome! You will learn a lot about your clients’ pov from the process, I think it will help your future business. Have you thought about designing it yourself to use as a marketing tool in the future?

 

[ToughButterCup]

Welcome.

I really like @Jilly's suggestion about designing it yourself: I bet though that there's not very much money in self-build design. We're all too cash-strapped.

 

Your comment about building networks  are exactly correct: it's a nightmare. Our local pub is - every evening - from 4:30 to 6:30pm full of white-van-men (no wimmin in sight: SWMBO hates it there before they all leave for their evening meal) . Just the kind of person you need now.

They come in to the pub with five jobs on the go , and leave with another three in prospect. I'm not suggesting that dipsomania is where building 'is-at', but the local building skills networks are as hard to break into  as any local golf-club or Rotary Circle. Find out where your Building-Network meets.  The issue tested (and is still - but less so-  testing me) to my limits.

Hence DIY - straight out of Project Management Theory - Three Pillars etc.

 

One Bhubber called coping with that barrier - DIYMAX. Gets the job done and you learn a lot.

Edited June 5 by ToughButterCup

[ProDave]

18 minutes ago, ToughButterCup said:

I really like @Jilly's suggestion about designing it yourself:

I thought being an architect, that bit was a given?

[Bournbrook]

Hi Sarah. We got planning a couple of weeks ago for a self build in Hampshire! Do drop me a message.  We are currently deciding between TF/SIPs and have found a good local builder. Going to the Build It Show on Saturday to hopefully get some questions answered!

[Sparrowhawk]

Hi Sarah and welcome to the forum, great to see someone else here from Hampshire!

 

We're renovating but if we had the option to knock down and rebuild I'd have jumped at it.

 

Any reasons not to seek PH certification? It means that the trades you get are held to working to a standard because their work will be measured, rather than "Yeah it's closeish and that's good enough".

[Iceverge]

Welcome welcome. 

 

It's nice to see new projects getting going. 

 

Moving from a bungalow to a two story is an interesting one. I grew up in a two story house but after numerous moves ended up in a single floor cottage before moving back into our two story. 

 

3 kids later I think I'd opt for a bungalow in hindsight. Yes for PH it's a poorer form factor but apart from the ease of living advantages there's lots of maintenance and construction benefits too. 

 

3 hours ago, SarahHutch said:

We are keen to use natural building materials wherever possible,

 

 

Any particular reason for this? Some aren't necessarily any more healthy or less polluting than readily available mass produced materials. 

 

Good luck.

 

 

 

[SteamyTea]

Welcome.

 

Reducing energy usage is really quite simple, the science is basic and understood well.

As @Iceverge says, there is probably no environmental advantages using "traditional" materials, and an awful lot of BS said about them.

 

We all like seeing pictures, so get a time lapse camera set up.

 

 

[saveasteading]

2 hours ago, Sparrowhawk said:

"Yeah it's closeish and that's good enough".

PH cf closeish?  perhaps about 5% loss in energy but 20% saved in build cost.  ?? more if all your suppliers are accredited and charge accordingly.

I'm guessing as I have not analysed it.

 

5 hours ago, SarahHutch said:

natural building materials wherever possible

If that means hazel sticks , mud and bracken then I would argue against it. 

Likewise straw bales.

 

I have looked into the latest fashions throughout my career, and seen them being specified by some Architects for some clients. 

It has never worked for me either on value or performance, but I'm up for being persuaded.

[Nick Thomas]

Hey hey. These folk aren't a *million* miles from you and might be interesting for the lime render part specifically: https://suffolkstrawbaleholidaycottage.wordpress.com/tag/lime-render/ . I assume if you're getting a timber frame from a supplier, you won't need the hazel sticks and straw bales  ^^.

 

Good luck and keep us updated!

Edited June 5 by Nick Thomas

[joe90]

Welcome. Lots of info here from folk that have been there done that . I built to passive esk standard (but no certificate) whatever materials you use my opinion is its success is down to the fine details (installed well and correctly). I don’t particularly like “plastic” insulation however under a slab it’s about all you can use, I used Rockwall elsewhere and like blown cellulose insulation. Keep us posted 👍

[ProDave]

One other thing, if you have spent a while designing developer boxes on housing estates, design your own home a LOT larger.  Don't confine yourself to a developer type house where you barely get room to walk alongside the bed and no room for a dressing table etc.  Be generous with your living space.  Our 5M by 4M bedrooms are about adequate.

[SteamyTea]

36 minutes ago, ProDave said:

One other thing, if you have spent a while designing developer boxes on housing estates, design your own home a LOT larger.  Don't confine yourself to a developer type house where you barely get room to walk alongside the bed and no room for a dressing table etc.  Be generous with your living space.  Our 5M by 4M bedrooms are about adequate.

Too true.

My living room is basically a corridor as it has a staircase in it.

 

Your bedroom is almost have the size of my whole house.

[Adrian Walker]

12 hours ago, SarahHutch said:

Hello,

 

I am Sarah an architect turned self builder in Hampshire. Having worked for the last 15 years designing new large scale new housing developments in London, I am now turning my hand to building our family home on the site of an old bungalow.

 

We have been living in the bungalow since 2022 and have a planning consent for a renovation project. However after much consideration we have decided to go for a knock down and rebuild, to ensure that we can complete the project to high performance specification, whilst reclaiming the VAT. We have submitted a new planning application and are awaiting the outcome of that.

 

We are seeking to build a two storey house, from timber frame (from Kithurst Homes) with a insulated raft foundation (Kore/Greenraft or similar). The house will be rendered in lime render with a clay tile roof. We are keen to use natural building materials wherever possible, and whilst we are not seeking passivehaus certification we are following passivehaus principals wherever possible. Ie. high levels of insulation and airtightness, MVHR, PVs etc.

 

We would love to hear from fellow southern self builders, as whilst we are familiar with the design process, we have limited contacts with local builders etc. so any recommendations would be greatly received. I intent to project manage the build myself and am happy to get involved with some DIY, but currently have limited skills in that department!

I’m self-building in Hampshire, neat Andover. Happy to help. 

[G and J]

13 hours ago, SarahHutch said:

with a insulated raft foundation (Kore/Greenraft or similar).

May I ask what the factors are that are driving this decision?

[Sparrowhawk]

14 hours ago, saveasteading said:

PH cf closeish?  perhaps about 5% loss in energy but 20% saved in build cost.  ?? more if all your suppliers are accredited and charge accordingly.

I'm guessing as I have not analysed it.

 

If you've got a principal contractor appointed and they have to meet the certification standards to get fully paid, it gives a well defined target to measure performance against. There's enough stories around of people who requested a "Passive house" (no certification) and didn't get the airtightness or thermal performance they were expecting. And I've seen the build cost difference put nearer 5%.

 

For self-builders I think closeish works fine, because we're motivated to keep up quality and do the best we can.

[SarahHutch]

Thank you all for the welcoming comments and advice. I am designing the project myself and depending on its outcome will see if it can be used for marketing in the future.......

 

We are keen the construction is as low impact as possible, hence the interest in natural materials passivehaus principals. However the sites orientation and a few design quirks mean that trying to get it passivehaus certified may prove complicated and costly. I will be on site everyday so intend to monitor quality closely.

 

With regards to the insulated raft foundation, this was suggested by our structural engineer as the best solution to achieve a high level of insulation with very minimal thermal bridging.

[saveasteading]

16 minutes ago, SarahHutch said:

this was suggested by our structural engineer as the best solution

but he isn't paying. check out the relative costs.

[saveasteading]

Thinking as a consultant  now, and also in your best interests why not compare and cost and justify all your decision's throughout the project.

I have found formalising it an interesting discipline.

I did it for a competition once, making it a measurable process. It cut through any prejudices the judges may have had... eg why aren't you using hemp? why have you no wind turbines?

 

[Kelvin]

Someone posted some excellent advice on here which I followed which was to do a simple cost benefit analysis of every major decision such as floor build up or insulation for example. Pick a value you’re happy to spend up to then really question when you go above this. 

[IanR]

Hello & Welcome.

 

57 minutes ago, SarahHutch said:

With regards to the insulated raft foundation, this was suggested by our structural engineer as the best solution to achieve a high level of insulation with very minimal thermal bridging.

 

And quite right he is to, although the edge detail needs marrying up with your chosen wall build up to achieve a fully thermal bridge free design. There's no reason why an insulated raft would not be more cost effective than a standard strip foundation (if comparing like-for-like), but, as they remain a niche product some company's continue to charge a premium for them, definitely shop around.

 

Are you going with Kithurst's I Joist wall build up? Looks pretty good, although there's potentially some cost that could come out of it without effecting performance. My own is an I Joist wall and roof structure, filled with cellulose fibre. From inside to out it's foil backed plater board, 300mm or 350mm I Joist, T&G DHF Egger board, breather membrane, battens, rain screen. The PB is the vapour control layer and the Egger board the airtightness layer (and racking strength), with no separate vapour or airtightness membrane (although all T&G joints were sealed with a butyl sealant). Really very simple and easy to make make very air tight.

 

Cullen Timber Design designed and engineered my frame, and in conjunction with Wilkinson Passiv Homes (previously Touchwood Homes) have completed quite few similar builds. 

Edited June 7 by IanR

[saveasteading]

6 minutes ago, IanR said:

There's no reason why an insulated raft would not be more cost effective

That interests me. I've seen many projects on here where there is very heavy reinforcement.  It is not usually necessary on good ground, but perhaps building on eps requires it?

It is very expensive and I don't know the reason for it, other than very cautious specification by supplier or SE. 

 

I haven't ever seen a costing for a raft on its own. that would be interesting and I am open to be favourably surprised.

[saveasteading]

16 minutes ago, Kelvin said:

a simple cost benefit analysis of every major decision

That's what I am saying. Some of the decisions can be complex, and it is another matter to include feel-good and carbon saving in monetary terms. But the latter can be client over-rulings  'just because it is my decision..

[Kelvin]

50 minutes ago, saveasteading said:

That interests me. I've seen many projects on here where there is very heavy reinforcement.  It is not usually necessary on good ground, but perhaps building on eps requires it?

It is very expensive and I don't know the reason for it, other than very cautious specification by supplier or SE. 

 

I haven't ever seen a costing for a raft on its own. that would be interesting and I am open to be favourably surprised.

The quote I got from Greenraft was £27k (164m²)but that didn’t include all the groundwork. 

[IanR]

59 minutes ago, saveasteading said:

That interests me. I've seen many projects on here where there is very heavy reinforcement.  It is not usually necessary on good ground, but perhaps building on eps requires it?

 

Many rafts and slabs are just over-engineered. It's not due to the EPS, I assume they've not been optimised by the SE.

 

My own, similar to many on here, has a single layer of A193 Mesh, in what is generally a 100mm thick "raft". The thickness is increased to 300mm under the external walls with a second layer of mesh and some extra rebar. The cost of the steel was easily covered by the reduced concrete, reduced muck away and no screed.

 

Edited June 7 by IanR