Building (labour & material) Costs for rear extension

[macadonald]

Hi Guys,

Been a while since I used the forum, was taking a few months break after two hectic years of DIY renovations that many of you gave me great advice with.

I have managed to free up some money from a remortgage to build a single storey pitched roof extension. The problem is that I don't think it is enough for a builder to simply come in and do all the work for me.

I'm trying to get ball park figures for labout & material costs. I know a builder will often increase the material cost to make more profit, but being reasonably capable, I hope to get hands on myself with certain aspects and have a builder who may be willign to do it this way.

Assuming I am goign to be building it out of double skin dense concrete blocks, with all of the insulation, tiled roof, french doors, windows and foundations, is there a means of calculating approximate material costs?

Perhaps a broken down spreadsheet someone has from their own job. Alternatively I guess, would be get quantities and I could then cost this up at the local buolding yard.

the extension will be the permitted 3m by 5m width..

Many thanks

 

[big-all]

a builder will want to make a living this includes any markup on materials
if you remove the income from materials the rate will go up to cover it

you can reduce your cost by grafting to the builders instruction

 

[macadonald]

Thanks Big-all, exactly what I thought.

Then on the assumption that I will project manage the work and buy the materials myslef so that I employ tradesman for each aspect of the build, is there an easy way to calculate or rough estimate for material costs for such a single storey rear extension?

 

[noseall]

Why on earth are you building out of dense concrete blocks?

Bomb shelter.

The mark-up is there for a reason.

If you buy all the materials then you are going to carry some of the liability for the materials. If anything goes wrong with any of the fabric of the building and it is found that it was installed correctly then the onus will be on you to rectify.

Then on the assumption that I will project manage the work and buy the materials myslef so that I employ tradesman for each aspect of the build, is there an easy way to calculate

By doing it this way you have made calculating the cost impossible.

For a start no one knows your level of construction competence.

A very broad costing figure is £1000 per m² (floor area). This is for the building work. Add on plumbing, heating, electrics, decorating, kitchens, bathrooms, cloak suites, ceramic tiling and a fruit tree in the back garden.

 

[macadonald]

Guys thanks for the 'advice'..

Not sure I understand why my construction competance or choice to purchase the materials myself would affect the material cost? I had always wanted to do a self build (bringing in the specialists when needed). I have done a fair bit of block laying and entirely gutted the inside of the house and rebuilt it, so think I will mange most aspects. I'm man enough to admit that I will need to employ specialist skills when needed though.

At the end of the day, my original question regarding material costs was to get a ball park figure (before labour). I unfortunately, will have a tight budget, but don't think that is a reason to not go ahead necessarily.

Have a good weekend all!

 

[noseall]

3m x 5m extension material costs in the region of 7k including spoil removal, plant, scaffold, skips etc.

 

[DeludedAussie]

3m x 5m extension material costs in the region of 7k including spoil removal, plant, scaffold, skips etc.

Is there no way to bring this down?

For example the spoil can be dumped at your local civil recycling centre or used at the back of your garden to make it a bit higher.

No need for a skip - again fill a hatchback and take it own to the recycling centre

So the only material you have is concrete at 100 cubic metre. blocks at 90p each, insulation and roof tiles all of which can be second hand on ebay

 

[ivixor]

Why not just build the thing yourself then? Submit building notice, handle inspections, etc.

Get a bricklayer in to build up off the foundations which you have laid to regulations. Get someone in to screed the floor too. The rest I would have a go at myself, including a flat roof with rubber top.

The way to calculate costs is simple: work out how much material you need, then get prices for it!

 

[DeludedAussie]

Why not just build the thing yourself then? Submit building notice, handle inspections, etc.

Get a bricklayer in to build up off the foundations which you have laid to regulations. Get someone in to screed the floor too. The rest I would have a go at myself, including a flat roof with rubber top.

The way to calculate costs is simple: work out how much material you need, then get prices for it!

I am trying to lear from other people who have done this before

I have yet to see a BREAKDOWN of where the money for an extension goes

I would love to see a spreadsheet which shows cost of digging foundations , cost of concrete costs of skips and so on so I can see where I can improve this

 

[badgeraudio]

This site will estimate your costs based on a set of plans.

But there is also a sample copy which might be helpful to allow you to estimate the cost your self!

http://www.estimators-online.com/samples-detail?type=single-storey-extension

 

[kingandy2nd]

I am trying to lear from other people who have done this before

I have yet to see a BREAKDOWN of where the money for an extension goes

I would love to see a spreadsheet which shows cost of digging foundations , cost of concrete costs of skips and so on so I can see where I can improve this

You really don't get it do you?! It doesn't matter what other people that have done extensions before have experienced/paid.

Their build will be different to yours! Different foundation requirements, different access concerns, different materials required, different labour costs, different different different different different.

I don't know what you persit on trawling this site trying to get this mythical 'breakdown' as you won't find it.

Quite frankly from your post/spam I have gleaned that basically you've bought a house that's too small and inadequate for your space needs so are basically explorining every ****ing option on how to make it bigger - extension, loft coversions, chimney removal etc etc.

The fact of the matter is that until you actually decide WHAT you want to do to your place, and then get it drawn up, you are never going to get an accurate price or a breakdown that you could use to see where savings could be made.

I reckon I'll see you and your house on DIY SOS in the near future so that'll be a good way to get a cheap extension... by getting the BBC to do it for you.

 

[peterperfection]

WHOOPS
Would have been a good idea to look at the date when Op originally posted the question --before these recent replies. .

 

[luisdesign]

I am loath to post given that this is of absolutely no help to the OP now... but I do feel I need to address one thing:

3m x 5m extension material costs in the region of 7k including spoil removal, plant, scaffold, skips etc.

Is there no way to bring this down?

For example the spoil can be dumped at your local civil recycling centre or used at the back of your garden to make it a bit higher.

Actually you are not able to do this - spoil, and more specifically hardcore is not accepted at many civic amenity centres, and where it is, it is usually highly limited and controlled. This is because councils are charged for the removal of this waste - This is the reason why people use skips, as the skip hire will include the waste removal fees. If they see the same guys coming day after day they will likely prevent you from depositing or charge you (over the odds of course) for the privelage.

again fill a hatchback and take it own to the recycling centre

When I re-decorated my bathroom I did this... just to take the tiles alone took countless trips. It's amazing how much space this stuff actually takes up. Add to that that the tiles were considered hardcore and I had to spread my journeys to the dump over about 5months! For an extension you'll be getting rid of spoil for years if you use this method!

So the only material you have is concrete at 100 cubic metre. blocks at 90p each, insulation and roof tiles all of which can be second hand on ebay

lol...

what about dpm, dpc, below dpc blocks / bricks, render, mortar, mesh, screed, wall ties, plaster, plaster finish, restraint straps, lintels, windows, doors, structural timber, ply, battens, felt, junction sheeting (ie: lead), guttering, downpipes, straps, architraves, skirting, nails, bolts... I'm not even scratching the surface.

Then you would also need to think about buying tools and plant hire... All the stuff a builder would already have.

 

[limerockconstruction]

Why not just build the thing yourself then? Submit building notice, handle inspections, etc.

Get a bricklayer in to build up off the foundations which you have laid to regulations. Get someone in to screed the floor too. The rest I would have a go at myself, including a flat roof with rubber top.

The way to calculate costs is simple: work out how much material you need, then get prices for it!

I am trying to lear from other people who have done this before

I have yet to see a BREAKDOWN of where the money for an extension goes

I would love to see a spreadsheet which shows cost of digging foundations , cost of concrete costs of skips and so on so I can see where I can improve this

Why would anyone give you access to their own intellectual property. If you want a breakdown, figure it out yourself, you seem to know how much everything costs.

 

[macadonald]

Wow guys,

My post appears to have come back to life after almost a year. I ended up building the extensions.

In short, demolished the old extension and dug out about 3 slabs myself.
Half dug the trenches and paid some cheap labour for one extra day.
Didn't use a skip, but rather a man and a van. He must have done 15 loads or more.
Poured the concrete myself.
Brought in a brickie and his team to build the walls in 3 days.
Laid the timber for the roof myself.

We then left for a month while builders did the dirty knock through. Carm back to it largely done, but did all the decorating myself.

Most of the materials I purchased myself which saved loads.

Taking on what I could, did undoubtedly save money, but as always, the total cost is more than expected.

Mac