Self build novice

[SueL]

Hi we're completely new to self build, we've renovated property before but never built from scratch. We've possibly located a plot - not purchased it yet - it has planning in place and services: elec, water and phone connection, but tricky access and a slope along one boundary. We're thinking of building using SIPs as we want a house that's going to be well insulated, quick to build and hopefully won't give us to many problems in relation to the access. I think it's going to be a steep learning curve so I'm hoping to find lots of tips and advice on the forum. I'm working out what we need to do next and have been reading about Conditional Contracts in relation to purchasing the plot and getting a Site / topographical survey done. Is there anything else we should be thinking about at this stage?

[TecTrevor]

Hi, have you thought about building insurance guarantee like NHBC or equivalent? 

[SueL]

Hi thanks for the suggestion, I'll add that to my list.

[Marvin]

Identify all the services to be used in your home. Consider heating and cooling requirements. Consider AIM: (Airtightness, Insulation and Mechanical ventilation with heat recovery), and if your going to go APE: (ASHP, Photovoltaics and Electric Vehicle charging).

 

Do a thermal loss and gain calculation based on the shape, size and thermal resistance of the building. Consider solar gain in your design. A well insulated building can easily overheat if this is not taken into consideration. Our renovated bungalow can overheat if the outside temperature rises over 10C.  Peak energy requirement at calculated temperature extremes indicates that we will need as much cooling on hot days 30sC as heating on cold days -8C.

 

Good luck.

 

M

 

 

 

 

 

[CharlieKLP]

Congrats I hope it goes well!
 

Most people start off wanting sips then realise you can get the required standard and speed with normal timber frame. Currently blockwork is being recommended on the outside of timber frame for insurance and warranty issues. 
 

You could be thinking about who you’re going to build with, depending on where you are in the country there are frame companies. I would use an external designer if you want something nice.
Some timber frame companies have a planning consultant service to help you through with planning and site drawings etc. 

 

If you have planning on the site already, I’m not sure what the benefit of a conditional contract is for you. But yes, get a topo and if it’s near other houses you will benefit from a street scene too.

[SueL]

Hi Marvin,

 

Many thanks for the information, I've started doing some research into some of those ASHP, MVHR..., what I'm not sure about is how to do a thermal loss and gain calculation, are there any good websites that explain how to do these?

 

Thanks

[SueL]

Hi Charlie,

 

Thanks for your response. We're still pretty open in terms of the construction method we want to use. We'd looked at SIPs because we want a building that's going to be thermally efficient and quick to build as we're going to be moving into rented accommodation. The site we're looking at also has tricky access which is going to limit the size of the vehicle we can get in, so we may have to consider off loading to smaller vehicles to get stuff in, although some SIPs companies will supply smaller panels. I've looked at a number of companies who supply SIPs kit houses and with most of them you seem to be able to adapt the design, and you can choose what stage they take the build to - wind & water tight or turnkey. But given the tricky access timber frame may be a better option. I've looked at MBC but haven't looked at any other timber frame companies yet (we're going to be based in Hampshire near Romsey). Thanks for the information about the blockwork and warranty etc, I wasn't aware of that. I'd Goggled 'building plot contracts' and found some information about 'Conditional contracts' and 'Option contracts' so that's why I mentioned those. As a first time self builder it all seems quite over whelming at the moment, so I want to make sure I'm doing everything right.

[IanR]

1 hour ago, SueL said:

We'd looked at SIPs because we want a building that's going to be thermally efficient and quick to build 

 

SIPs don't really deliver their headline "quick build" for a bespoke self build. There may be less build-time on site compared to some build methods but that's balanced out with more frame design time and factory time constructing the panels.

 

You may actually be committing money earlier in your program with a SIPs build, and may therefore need to be in rental accommodation earlier and for longer.

 

With regards to being thermally efficient - there are better options. A SIPs structure won't deliver the advertised standard panel U value. With roofs especially, but also walls, additional timbers will need to go in to the panels to carry the loads, and these reduce the whole panel U Value and introduce cold bridges.

 

Reasonable airtightness, compared to building regs, can be achieved with SIPs but it's a difficult build method to achieve excellent air tightness. If you look into the Potton case study of building a SIPs PassivHaus they comment on the extra work it took to achieve the air tightness targets.

 

You don't say whether you are considering combing SIPs with a masonry skin. I'm personally not a fan of PIR/PUR insulation in general, but combined with a light weight rain screen (timber cladding, render board etc.) I'd definitely steer clear. The low decrement delay of PIR/PUR means it really should be combined with a "heavy" outer layer to avoid uncomfortable internal temp swings 

[SueL]

Hi Ian many thanks for your comments and advice, certainly lots to think. We're still undecided about which method of construction we're going to use so all this is really useful information. You said "With regards to being thermally efficient - there are better options" any suggestions for what these would be?

[IanR]

3 hours ago, SueL said:

 any suggestions for what these would be?

 

Depends upon your energy efficiency (heat loss) aspirations, whether you need a masonry skin for planning, your feelings about timber-frame houses and whether you have access to any particular construction trade via you, family or friends that would make one or other construction type more cost effective.

 

An I-Joist or twin-stud (Larsen Truss) timber structure, filled with blown cellulose fibre insulation, combined with an insulated, ground bearing raft (foundation) and timber or render board clad, I would say, is the simplest construction method to achieve a very energy efficient build. A light weight timber structure makes the insulated raft simpler (and cheaper) to design cold bridge free. If you have to have a masonry skin then it may make an I-Joist or twin-stud structure more expensive than alternatives

 

I'm not so familiar with insulated concrete formwork, but there's a few members here that have built ICF houses that perform to a very high level, with some building the ICF structure themselves. If you are not up for getting trained and doing it yourself you may struggle to find experienced trades to do the ICF build for you.

Edited May 9, 2022 by IanR

[Thorfun]

if I had my time over again I would get an I-Joist/twin-stud (Larsen Truss) with blown in cellulose. I saved a small fortune getting open panel timber frame and fitting the insulation myself but I doubt I'd do it again.

[Jilly]

Think about living in a static on site and selling it, many self builders do this. My build went over time for lots of reasons and I could have done without paying nearly £20K in rent. It would have been great to be able to pop out and do small jobs in the evening or handle deliveries in the evening on winter. Don't underestimate the stress. 

[Faz]

SIPS are far more expensive than timber frame and, these days, they are virtually the same thing. We did a penthouse scheme in 2019 and the cost for SIPS was £180k vs £47k for the timber frame.  Check Buildzone for the warranty - the cost for a self build warranty for my 3000 sq. ft. house was £2k - I do have a good rating with them for spec plots which probably helps mind.

[CharlieKLP]

Can I spam the brief document to you? People seem to like it. The link is in blue half way down the page.
 

https://www.potton.co.uk/self-build-resources/designing-your-home/creating-a-design-brief

 

I think it might help to get your thoughts in order. I would speak to a planning consultant to get an idea how high and what style you can get on your plot next. When you know your budget.

[DevonKim]

I have found that design brief really help @CharlieKLP - it helps you get your thoughts in order and work out your priorities.  I recommend it as a good starting point @SueL

[SueL]

Many thanks for all the information, lots to think about. We didn't get the plot we were initially looking at, so its back to the drawing board.

[Thorfun]

1 hour ago, SueL said:

Many thanks for all the information, lots to think about. We didn't get the plot we were initially looking at, so its back to the drawing board.

speaking from experience...make sure you don't spend money on the self-build until you've exchanged contracts on whatever plot you find. we thought a property purchase was going through and so we paid an architect to design a new house, paid for topography reports etc only to be gazumped 2 weeks before exchange. so that was a substantial amount of money down the drain.

 

we learnt that lesson the hard way. for this the day after we exchanged contracts I phoned up architects to get them round to view the plot safe in the knowledge that any money I spent I could sue the sellers for if they didn't complete after exchanging contracts.