Class Q - Steel portal barn conversion cost estimates

[Stoph43]

@Dave Jones is this just a swooping comment or is this based on actual figures you've experienced? Thanks

[saveasteading]

6 minutes ago, Stoph43 said:

'm guessing you've had to apply for full planning approval for this

The outer skin passes the column here and is probably more than your allowable thickness. but not much.

I wonder if anyone knows how much or little constitutes complying?

And is there a dimension recorded at the planners?

 

If it is a problem then is it possible to shave off the necessary amount of eps, and inset the blocks?

OR inset the whole wall to line up with your permitted building line,  and then overlay the gap at the column with PIR to the available thickness.

 

[Stoph43]

On 03/12/2022 at 17:24, saveasteading said:

 

As there is wall cladding then that would define the available outer limit. so you have 20mm or more to play with, if anyone is measuring that closely.

 

But then what if you drop a string line from the edge of the roof  sheeting, does that give extra width?

 

Even if you could only squeeze in 20mm PIR outside the columns, that will do enough, and can be made up for in other ways (discuss later if this works in principle)

 

I do not agree for a moment that you should leave the rafters and purlins exposed, if that is what the above suggestion is. It would need heavy protection and would be , let's say, quirky. It works in the Mediterranean but not here.

 

Are the purlins  (pedantic corner here...purlins are only on the roof, the walls have wall rails (or girts  in American and some of Europe))

yes, are the purlins set on top of the rafters or inset?

 

What do you plan for the wall construction?

 

You will be stripping the wall and roof cladding. Has anyone already measured the existing dimensions?

 

This is all worth many thousands to you, so any more photos or sketches may be worthwhile.

 

Really interested to hear more on your builds sound sliek you have lots of experience on different projects with this. It really depend on how the LPA feel and see it. In my area they are really against any class Q and are renowned for being difficult, so the project is really in their hands. If we get class Q ( which we tick all the boxes to say we should) then we'll apply for for planning to try and take the advise from all of you guys to knock down and start again. We really don't want anything different, the current footprint works fine, it's just a build method around the steel portal. which is really undecided still

 

I like the idea of ICF, but it would need new foundations  so full planning, just trying to look at backs options, no one has actually measured the barn yet another that the architects rough dims. part of me wants to try and add to the structure before it measured so we can squeeze som insulation and structure in as well as eth steel cladding.... it all seems like ridiculous class Q game, just to try and make the building energy efficient without losing footprint

 

Purlins are set onto the steel portal frame (rafters?) and the fibre cement boards are fixed to the purlins (excuse me if the wording isn't correct

 

[saveasteading]

On 04/12/2022 at 14:32, Dave Jones said:

take the m2 cost for a standard build of the same size and double it. 

 

Yes if the condition is poor and you are in the hands of designers.

No, x 1 if it is in good condition and you can use the structure to your advantage.

The downside to me is the constraints, not the the cost.

Or anywhere between.

 

Stoph 43 you can see that I think it can be done at economical cost, while some others say it can't. We are both right, as we don't know the project, your team, or you.

[saveasteading]

32 minutes ago, Stoph43 said:

excuse me if the wording isn't correct

 

Full marks.

Have you checked if the fibre-cement is asbestos free? It looks as if it is modern enough to be polypropylene not asbestos.

If so, it doesn't have to come off and you can build above it for insulation and weather (IF allowed for height) and below for appearance.

But you might choose to strip and start again anyway, but keep the purlins.  IanR solution.

 

Returning to question 1. What is the cost? 

I don't know. 

Most people are saying about £2,000/m2 for new-build. 

If that is accurate I can only advise you to allow more, for the hassles and unknowns, and perhaps designers who don't want (or understand how)  to optimise  with what is available.

 

For example I have seen loads of designs which say to beak out all the concrete slab, then rebuild. I wouldn't, but they have. Not their money, or it didn't cross their mind.

 

Did you ever tell us approx area of the country? You don't need to, as all this discussion is publicly available in a search.

[Tosh]

On 06/12/2022 at 16:57, Stoph43 said:

I'm guessing you've had to apply for full planning approval for this rather than a class Q? 

TBH we bough the site already with full planning for change of use to residential (previously commercial) and to convert building to domestic dwelling. We then submitted a couple of S73's to get the design we wanted as the initial planning was awful. During this we tested the water with the planners to take down the frame but they said that would constitute a new build in the open countryside which was against policy hence we conceded. But conceding that gave us some leverage to get the finished look we wanted which initally they were against - give n take so to speak. Few photos, not sure if they'll all load..

 

[saveasteading]

2 hours ago, Tosh said:

TBH we bough the site already with full planning

Thanks, that is helpful and we can concentrate on what is possible.

 

Would you like to summarise any outstanding questions, and any fundamental constraints from your own aspirations.?

[Tom]

10 hours ago, Tosh said:

TBH we bough the site already with full planning for change of use to residential (previously commercial) and to convert building to domestic dwelling

Looks like you came up with a good solution to the constraints of the conversion, but (correct me if I'm wrong) it doesn't sound like you had "full planning", more like permitted development rights for change of use. Full planning permission would have allowed you to build a new house, rather than convert what was there. 

[Tosh]

3 hours ago, Tom said:

but (correct me if I'm wrong) it doesn't sound like you had "full planning", more like permitted development rights for change of use

Thats incorrect, it is Full Planning. This principle was made clear in the planners pre-app report. The principle on which full planning was granted for change of use and development is that it is a rural conversion. As mentioned previously in our area at least new build in the open countryside is against policy and they said permission would not have been granted. Hence why I had to retain some element of the structure to 'convert'.

I've not heard of PD rights for commercial premises but wasn't applicable to us as we'd already purchased it with full planning.