Self Build Novice - Navigating Minefield of Options!!

[Lucasgrantmaw]

Hello All,

 

My wife an I have secured our ot of land and have attended a number of building shows and its a minefield of options. 

 

The key decisions we are looking at are

 

1. Building methods - looks like brick and block are a thing of the past. Should we look at ICF or timber frame with SIPPS?? 

 

2. Our foundations could be complex due to soft soil, clay and tree roots. Is piling still top dog or has anyone used ESP foundations? 

 

3. Is the air source heat pump good or not??? So many conflicting opinions. If not? What's the alternative??

 

Would appreciate some thoughts on the above? 

ISOTEX_brochure_V3.pdf EPS_brochure_V_2019.pdf

[nod]

Brick and block are definitely not a thing of the past 

We have chosen solid over timber Frame on our last build and current one partly  due to the difference in cost 

I have worked on both for many years and prefer solids to TF 

But if you want convenience TF or Sips is definitely that 

 

Don’t be pushed into piling 

We used deep strip and Clay board on our last build Clay ground and hundreds of 10 meter trees to three sides 

 

Gas boiler on our previous 

HP on our Current build 

Expecting it to be significantly more expensive to run than our gas boiler 

But no gas in the area So not an issue 

 

All the build shows that we visited are poor r also ons of the NEC show 

Excellent 

 

[Temp]

We opted for brick and block and would do so again but with more insulation.

 

7 minutes ago, nod said:

Don’t be pushed into piling 

We used deep strip and Clay board on our last build Clay ground and hundreds of 10 meter trees to three sides 

 

+1 We are on clay with trees within 3m. We were also allowed strip foundations with compressible boards.

 

It might be worth getting a proper ground condition report done to ascertain how good/bad it is.  This involves digging two trial pits and pushing specist instruments into the ground and soil samples sent to a lab. You can save money by getting the percolation test done at the same time if thisvis needed to prove and size soakaways. Even more if you can provide a JCB and and/or water supply, although they can usually arrange these as well.

 

A raft foundation might also be an option. 

 

 

[Iceverge]

Welcome @Lucasgrantmaw

 

You can build almost any style or type of house out of anything but some styles lend themselves to different methods. 

 

Do you have planning permission? Do you have a budget to work to. Do you have any special requirements for the house? 

 

We used block and block. Strip foundations. Passive house spec. One small heater keeps the house comfortable. 

 

pros

1. Cheapest option 

2. Ready supply of materials and skilled labour. 

3. Easy to insure, engineer, and explain. No educating professionals or searching for specialists. 

4. Low risk of suppliers defaulting. 

5. Very quiet. 

6. Weather tolerant

7. Durable. 

 

Cons, 

1. Messy

2. Slower

3. Huge embodied carbon. 

4. Not nice to install services or drill holes .

 

 

 

 

[Temp]

Heat pump vs gas boiler...

 

Historically the electricity used to run a heat pump has been three times the cost of mains gas when comparing like to like, however a correctly installed heat pump has a COP of 3 so the running cost should be similar.

 

Heat pumps tend to work better in well insulated houses with UFH. If you are planning levels of insulation much better than the minimum required by building regs I'd probably go with a heat pump. 

 

First make sure you can get a decent electrical connection eg 100A. Especially if you want electric showers and a car charger. It's not unreasonable to install a three phase supply in some cases. 

 

Edit: Servicing can be more an issue with heat pumps but that should get better. If someone recommends a particular heat pump check there are people in your area that can fix any issues. Try ringing around asking if they can fix a problem on an xyz?

 

Edited January 16, 2023 by Temp

[JohnMo]

As @Temp says well insulated house with UFH heat pump will be cheaper to run.  Heat pump give great efficiency if the flow temps are low. The thing with heat pumps the design needs to be well thought through. Your mentality needs to be different from normal gas, as they won't work that way without you needing a second mortgage.

 

Your cylinder needs as big a coil as you can get 3m2 or better. Your run times for UFH or rads need to be long and low temp. Buffers will kill efficiency and so will lots of zones.  Done right SCoP of over 4 should be achievable.

 

If you want your heating on a couple of hours in short blasts and lots of zones, then gas maybe a better choice.

[Thorfun]

might be worth looking at an insulated slab for foundations? obviously your SE will design what's suitable but i was of the understanding that a raft/slab foundation works ok on clay. also agree with the comment on getting a proper ground investigation done. it's what your structural engineer will work off.

[saveasteading]

21 hours ago, Lucasgrantmaw said:

soft soil, clay and tree roots. Is piling still top dog

My thing.

Tell  us more about the ground, tree varieties and distances and the optimum answer should be clear enough.

NB not all Architects and SEs know the  relative costs of methods.

For now, assume piling costs for reasons of caution, and we can try to save cost later.

 

Re the building structure. to some extent it depends on the building. Simple shapes suit kits, complex shapes suit being  built on site.

That could also affect the foundations decision.

 

13 minutes ago, Thorfun said:

proper ground investigation

This doesn't always need to be complex. If you find an SE who knows your local ground conditions, then a couple of holes dug with them in attendance may suffice. Are / have any other houses being built nearby?

[Thorfun]

2 hours ago, saveasteading said:

This doesn't always need to be complex. If you find an SE who knows your local ground conditions, then a couple of holes dug with them in attendance may suffice. Are / have any other houses being built nearby?

this is a very valid point but for us the GI gave us soil composition, water levels, CBR rating, percolation rates, radon levels and many many other things so it was quite invaluable. the SE used a lot of the information and the CE also used it for their design of the driveway and crossover. 

 

in the grand scheme of things it wasn't stupidly expensive either.

[saveasteading]

5 hours ago, Thorfun said:

In the grand scheme of things it wasn't stupidly expensive either.

Quite right. It can allow the SE to be precise rather than sensibly  cautious, and save more than its cost.

I just mean, work with the SE  and that is likely to be a relevant but not overblown report.

[twice round the block]

@Lucasgrantmaw

I'll answer the soil survey question as I'm sort of collaborating on this build with Lucas.

 

An in depth soil survey was done in 1996 due to the current property subsiding. As a result 32 piles were put in to a depth of 7m below the property and a raft built on top of them below the existing footings.

Nothing has changed on site regarding the sub soil make up.

Due to the positioning of the original property, this will be demolished and a new property will be built to make better use of the plot orientation and will not use any of the original piled foundations.

The rest of the information Lucas and his wife will need to make everything happen will be down to them too research along with other forum members on here to help them unravel some of the complex issues with a passive house build.

 

That's my two pennies worth, I'm off now to build some garden walls when the weather sorts itself out.

 

 

[saveasteading]

if you want any more thoughts on the ground and foundations, then we would need to see the report, or at least the summary.

But thoughts is all it can be at this stage.