Material Costs

[thomp1983]

Hi All,

As a backup plan if our house doesn't sell I'm looking into the possibility of an extension, I want to apply for planning permission whilst it's on the market so I'm ready to start building the day we can take it back off, whether we go ahead with the extension will all be down to cost and there's a few things I need a hand with.

Here are the plans and a few pictures of the house currently.

I'm basing the design on the idea of building 3 brick piers where the 3 6ft fence posts currently are with rsj's on top of the pier and garage wall then 2 maybe 3 across to the house to make the floor (A structural engineer will be used for this if the costs look viable)

I'll be doing all the labour so the prices are purely for the materials,

Roof Tiles/Battens/Membrane £1000
Roof Trusses £1000
Brickwork & Piers £1000
Foundations £1000 For 14m Trench 600mmx1m deep If I have to replace garage foundations

I need help with what the rsj's may cost and what will be required, The new rooms above the garage will be housing 2 bedrooms and obviously the roof will be a reasonable weight is my idea of using 3 piers feasible or would I be better using steel columns covered in brick slips.

Also how would I seal the bottom of the floor from the outside weather? inside the garage I could just insualte between the joists and plasterboard as required but what would I use outside the garage door, I assume there's a plastic sheet material for the job?

I'm hoping to be able to build the weather sealed shell of the extension for 10k or under with a total finished cost of 20k depending on exactly what we do internally.

I've not costed the windows as the odds are we would replace all the windows in the house which would be a seperate cost to all this work.

Also with regards the roof as there is already a small extension on the rear with a pitched roof draining onto the flat garage roof I planned on draining the rear of the new extension roof onto the roof the same, I can't see a way of fitting any sort of pitched roof to the garage roof so think a flat roof on the garage is the way to go

Thanks
Chris

 

[domdee]

This dormer conversion cost my wife's friend around £55k with builders in doing the work. We are east Yorkshire so one of the cheaper parts of the country.

https://newplanningaccess.eastridin...s.do?activeTab=documents&keyVal=Q6M6E5BJ0TC00

 

[kingandy2nd]

Don’t understand the brick piers/rsjs rather than a standard wall.

Double your budget, possibly triple, and you’ll be closer to the true costs.

Good project though, best of luck with it.

 

[thomp1983]

Piers are to allow light in, the main door to the house is that side and if I put a brick wall the whole way along alot of light will be lost into the downstairs entrance.

As for costs we only spent 30k renovating all the rest of the house including removing internal walls, the driveway, a new kitchen and bathroom so I'm fairly confident I can keep to a budget and don't think for materials what I've listed so far is unrealistic

 

[kingandy2nd]

I see, so the ground floor is partially exposed still.

Proper plans 500
Planning app 200
Building control 500-750
Soil removal 400
MOT1 300
Floor slab concrete, 700
Insulation (floor, walls, roof) 1000
Windows, 800
Lintels 300
Structural engineer 250
Rsjs 500
Skip 250

Truss and roof material costs seem too light to me given you’re going to have a quite a lot of surface area to cover. I’d budget 2k.

Another 6-7k or so there, without any of the odds and sods that you’ll spend a few £100 on there and there.

What’s your tool set like? Cement mixer, 300, wacker plate 300, digger 300 (hire), levels and trowels 150, angle grinder 100, genie lift 150 (hire), scaffold ??? Couple of grand in there maybe.

No trying to pee on your campfire, just sharing a bit of experience as a diyer myself that’s about 60% of the way through, and £30k so far into my own double story extension.

Hope that helps.

 

[mikeey84]

I'm no expert but it looks like you'll need the best part of 700 quids worth of concrete for the foundations, is 300 quid going to cover plant hire and disposal of soil?

I can't comment on the other costs, but from the many threads I've read on here, and my own experience, £10k seems very optimistic

 

[thomp1983]

Thanks for the replies,

Disposal of the soil removed would be via my trailer to the local tip which is fortunately a mile away, that's how I did the driveway which I'd guess was a similar amount of soil.

A man with a digger is £200 a day which I would only need if I have to dig a whole new trench foundation, if the current garage foundations are deep enough I'll hand dig the short bits needed at each end.

I have 2 cement mixers and access to a whacker plate, the rest of the tools I mostly already have or have access to borrow (this isn't the first thing I've been involved in building but it's the first of this design and solo lead)

 

[23vc]

You’re planning on digging a 14m 1m deep trench and disposing of the soil in your car trailer? Sounds absolutely bonkers unless I’ve misread it. Surely that’s at least one 16ton grab wagon load, or many skips

 

[kingandy2nd]

Crack on mate, sounds like you’ve got it all sorted

 

[thomp1983]

not sure why this has wandered off into a discussion about disposing of spoil but,

that's a 10m wall dug to 500mm deep, all the soil was placed on tarpaulins on the font drive then loaded into my trailer and taken to the tip, diggin it by hand and disposing of it all took 3 days, 2 days digging, 1 day removal, I understand how to some people paying for a grab lorry at £300 makes more sense but to me I'd rather put in a full day of physical labour and save that money for something else, yes I know the foundations will produce roughly twice as much waste but to me I'd still rather put in 2 days getting rid of it after using a differ to remove it, it's one of the few ways as a diy project you can save money over what a builder needs to do to get things finished.

as for knowing what I'm doing there are obviously some things I don't know hence the need for this thread but how a plan to deal with the waste and the trade offs from that isn't one of them.

Chris

 

[23vc]

Fair enough mate, my post was purely aimed to help, and didn’t realise I was wandering off your topic. if you’ve got it in hand then great. I always find soil ends up so much bigger when it’s out the ground

 

[mikeey84]

I think it was me that started it wandering.

Apologies for that, it was just an example of a cost I thought you hadn't accounted for.

Always difficult to spec RSJs from a photo, but they are not that expensive in the grand scheme of things.