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Outbuilding construction drawings quote


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Hi,

 

I was quoted £1200 to produce construction drawings for a 10m by 6m simple rectangular building with a pitched roof (to be built under PD). A further £600 is projected to be SEs fee - my understanding is it's on top of the fee for the raft foundation. Does this sound reasonable? The build method is not fixed yet and we plan to agree on it before moving forward.

 

Separately, I would like to have vaulted ceiling, ideally no joists. Is this technically possible? Feasible? Can't find spans that would give me a definitive answer. 3m rafter run is clearly not a problem, 10m glulams seem available, but would the load (SIPs or similar well insulated construction) be too high for this? Concerned because the message I was given was

>> A light weight steel frame with infill timber or block panels / load bearing block & joist roof but the spans would need to be reduced with steel posts

 

TA.

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14 hours ago, DevilDamo said:

Although not directly answering your questions, but I have a few questions...


- How close to a boundary is the outbuilding to be?

- What is the outbuilding to be used for?

- What is the floor area of the existing dwelling?

The boundary - at least the boundary line - will be 1m+. Since it is a row of shrubs there may be slightly less than a metre from the branches. 

The outbuilding is planned as an office /gym, although we hope to be able live there if we ever get to rebuild the main house. 

The total floor area is 110m2 IIRC. 

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6 hours ago, Dave Jones said:

Why are you bothering with either  for a square box that you wont be living in ?

Sorry, what do you mean? BC? Insulated slab? Wrt to the latter, as above, I expect to be spending quite a lot of time there. I like comfort and I want to be able to drop a weight without worrying about breaking the suspended floor. ?

 

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1 hour ago, oldkettle said:

The boundary - at least the boundary line - will be 1m+. Since it is a row of shrubs there may be slightly less than a metre from the branches. 

The outbuilding is planned as an office /gym, although we hope to be able live there if we ever get to rebuild the main house. 

The total floor area is 110m2 IIRC. 

 

So you can get a pitched roof designed to come under 2.5m on a footprint of 10m x 6m?

 

The PD rules for outbuildings do not include for it to be used as a residential dwelling/annexe, so be careful there.

 

Although under PD there are no specific rules on how big outbuildings can be, their size has to be relative to the existing dwelling. I can't see the LPA agreeing to an outbuilding under PD, which is more than 50% of the floor area of the existing dwelling to be relative/ancillary.

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21 minutes ago, DevilDamo said:

On that last point, have a review of the attached.

Outbuilding.png

 

I appreciate this. However we already have planning in place to extend the house to 200m2 and our garden is quite large. Taking into account we both have been working from home this is actually our best bet to get our own offices soon (we both get calls quite often). The gym I have in mind requires some space and one of the reasons I want a vaulted ceiling is to allow me to perform certain exercises. Also thinking of getting a ping-pong table at some point - we both like it very much, don't want to be hitting the joists constantly ?

 

With regards to using as a dwelling, obviously, there are no such plans. A temporary habitation strictly as long as the main house is not habitable is a different thing. 

Edited by oldkettle
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1 hour ago, DevilDamo said:

So you can get a pitched roof designed to come under 2.5m on a footprint of 10m x 6m?

Sorry, missed this bit. 

Aren't we allowed 4m ridge? 

Ah, I see you point. 

This just means we will have to step 2m away from the boundary on the gable side. There is plenty of space for this. 

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1 hour ago, dangti6 said:


I believe they compare it to the size of the ‘original house’, excluding any additions.

 

They seem to be referring to the existing house?

As long as I have something to fill this place - which I will do - I am not worried. It is not wider than the existing house and will be 30m away. Much more concerned about actually building it. 

Edited by oldkettle
Typo
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On 12/11/2020 at 21:16, oldkettle said:

Separately, I would like to have vaulted ceiling, ideally no joists. Is this technically possible? Feasible?

 

Im sure you know that the issue that must be addressed is the weight of the roof pushing the walls out. This is normally achieved by triangulation/joists but another way is to use a structural ridge beam...

 

This works by using a steel or possibly a large wood beam instead of the normal thin ridge board. The ends of the beam carry the majority of the weight of the roof so must rest on padstones in the gable walls or possibly on steel or large wood posts that go down to the foundations. If possible avoid having doors or windows in the gable walls as that can complicate things. The rafters should meet above the ridge beam and be connected together (perhaps with steel straps) so they effectively "hang" from the ridge beam.

 

There are versions of this that use purlins to carry some of the load. These also reduce the unsupported span of the rafters and consequently their dimensions can be smaller.

 

Lot depends on what the roof covering is going to be - tiles are much heavier than polycarbonate sheeting!

 

https://www.beamcalculation.co.uk/start-calculation/steel-ridge-beam/

calc-25.png.351463a297aee4a2a56da35392b0c70e.png

 

Edited by Temp
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1 hour ago, Temp said:

 

Im sure you know that the issue that must be addressed is the weight of the roof pushing the walls out. This is normally achieved by triangulation/joists but another way is to use a structural ridge beam...

 

This works by using a steel or possibly a large wood beam instead of the normal thin ridge board. The ends of the beam carry the majority of the weight of the roof so must rest on padstones in the gable walls or possibly on steel or large wood posts that go down to the foundations. If possible avoid having doors or windows in the gable walls as that can complicate things. The rafters should meet above the ridge beam and be connected together (perhaps with steel straps) so they effectively "hang" from the ridge beam.

 

There are versions of this that use purlins to carry some of the load. These also reduce the unsupported span of the rafters and consequently their dimensions can be smaller.

 

Lot depends on what the roof covering is going to be - tiles are much heavier than polycarbonate sheeting!

 

https://www.beamcalculation.co.uk/start-calculation/steel-ridge-beam/

calc-25.png.351463a297aee4a2a56da35392b0c70e.png

 

 

Thank you. This is exactly what I had in mind and the reason I mentioned glulam. With sips the load does not sound too bad. I am just trying to get an idea for what is possible: maybe 10m is indeed too much, maybe not. 

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14 hours ago, dangti6 said:


I believe they compare it to the size of the ‘original house’, excluding any additions.


Assuming the OP would be going down the LDC route, the LPA would asses the size of the outbuilding in context with the existing dwelling at the time of the submission of an application. So it’s always advisable to extend a dwelling prior to applying for a large outbuilding. The only potential issue with this is that LPA’s can look to withdraw PD rights following grant of ‘formal’ Planning.

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1 hour ago, Temp said:

 

There is a list of appeal decisions here..

 

http://www.permitteddevelopment.org/Incidental-Use-Appeal-Decisions.php

 

Some large outbuildings were refused but some were approved at appeal.

 

 

 

Thank you for the link. No proper rules exist in this area, no consistency. You can have a bathroom. No, you can't. You can have a pool. No, you can't. Somebody who doesn't attend a gym is telling people what size they believe is suitable for a home gym. 

If the neighbours / council are concerned that people rent accommodation out then they should go and prove it. Otherwise I can't quite figure out what their problem is. 

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