Cost of selfbuild

bailey#

Just wonderig what the difference in cost per sq foot of building a house with a contractor and without? is it worth while managing the project yourself

LowOdour

Probably one of the most asked question Construction & Planning! You should read the stickies, probably find something in there to help you. Abit like myself, would love to know how much my self-build will cost, but every house is different so would be hard to get just one price.

The best way to get an answer is to send your plans out to contractors and tradesmen to get a ballpark figure of your costs. Thats what il be doing once my planning comes through

mr_edge_to_you

We've gone the contractor root. It may be more expensive but 7 weeks in and our roof should be started by the end of the week. The best advice I can at this early stage decide what you heating system you are going to use and what type/spec of window you want. These are two costs alone could be up to 25percent of your budget. Spec your house and then prepare a budget! See if you can afford the contractor then. You must also consider the skills and work you can put into a direct labour build and you will need someone to oversee the project. You will save a few quid, no doubt about it but be prepared for taking on a 2nd full time job.

bailey#

thanks for replies, just asking as am going to build bit by bit as savings will allow. cant sell present house and couldnt get second mortgage, so jst wanted to make a start until savings run out, which isint a whole lot:D

soldsold

mr_edge_to_you wrote: »

The best advice I can at this early stage decide what you heating system you are going to use and what type/spec of window you want. These are two costs alone could be up to 25percent of your budget. Spec your house and then prepare a budget!

Or spec your house design to maximise passive solar gain and maximise insulation to reduce your heating needs as much as possible for the rest of your days in the house. Go mental on detailing to make sure the insulation is installed properly. Then your heating system becomes a minor issue.

100mm EPS floor insulation is just over 6 euro per metre2 at the moment. 200mm or 300mm EPS floor insulation si therefore 12 euro per m2 to 18 euro per m2 plus vat - not huge money. 100mm rockwool flexi is about 8 euro per metre2. Pumped attic insulation is 10 euro per m2 for 12 inch deep insulation - or 14 euro per m2 for pumped insulation in sloping rafters. All quotes I have got in the last month.

If feeling adventurous then spend 1000 euro on airtightness testing and buy some airtightness tape and fix the leaks. It will pay back in about 5 years.

Specify basic, cheap building products that have airtightness built in - wet plaster, taped OSB board.

Get rid of the open fireplace and put in a sealed stove with its own air supply through 100mm pipe under the slab.

Spend 6k on an 85% efficient mechanical heat recovery ventilation system that will save a few hundred euro per year. Just make sure to service it like you would your car.

Compare the above to quotes of 20k, 25k for geothermal or high output boilers that eat energy for as long as the house will stand.
Instead, buy a small condensing boiler to meet a drastically reduced heating requirement.

Agree about windows though, but decide on the windows/ heating spec based on some science such as DEAP or PHPP software instead of a finger in the air guess by a plumber who will overspec the boiler/ geothermal unit "just in case" so it runs inefficiently for ever.

Finally, decide if you want to go this direction (to me its a no brainer) and then decide if you would trust a builder to build a house to this exact spec without missing anything - very unlikely unless you get a builder that has a belief in airtightness/ energy efficiency/ detailing.

I'm going the selfbuild route for a 250m2 extension, there is no way I would trust it to a builder.

However, there are many posters on these forums that are builders and by posting and reading here they are miles ahead on the above topics than the general builder.

So selfbuild, or get a builder that has a mission to build decent houses. It will be worth paying a bit extra to get the structure 100%.

soldsold

Builders will have done the research to know where the cheapest materials can be got, and can buy in bulk for the best rates.

If going selfbuild just be prepared for lots of phone calls to suppliers and lots of bouncing between suppliers haggling for the best price, or the money you save on selfbuild can get eaten up by paying top dollar for materials.

Also consider lumping jobs together - eg foundations and block walls instead of pricing separately - you might get a better rate.

mr_edge_to_you

soldsold wrote: »

Builders will have done the research to know where the cheapest materials can be got, and can buy in bulk for the best rates.

If going selfbuild just be prepared for lots of phone calls to suppliers and lots of bouncing between suppliers haggling for the best price

be prepared for phone calls to and from everyone.when things go wrong it is you and you alone who is responsible.i should add that you need to be on site daily to ensure the work is being done right. I've had 2 call from our builder. 1st was getting details of our heating supplier and the 2nd was because he lost them!