Examining the 'house sandwich' - working with 8250mm

[joth]

5 minutes ago, DevilDamo said:

I appreciate LPA’s vary up and down the country but a bat survey amongst other reports and surveys are normally validation requirements. So these would be “ticked off” prior to the formal registration of the application as opposed to being brought up at the end. That is of course assuming the LPA are efficient. If changes are required during the formal determination process and of which are considered to be minor, the LPA should be able to accept revised drawings, which replace the previous. If the changes required are considered to be material, the LPA in most cases would have to re-notify the neighbours along with other consultees and may request an extension of time. Again, this is all assuming the ‘efficiency’ of the LPA.

Just to clarify, by "here" I mean in the specific planning authority where the OP is going to be placing their planning application (we live in the same town), and which is widely regarded as one of the most expensive and least efficient to deal with.

(Our own application (a simple renovatin/extension) was delayed 5 weeks because  as the end they realized they'd incorrectly reissued the original plans to the local parish council when we made a minor amendment early on. I spoke to the parish council and they said they don't even look at minor amendment after approving the original plans, so I was at least able to gee up the district council a bit when I shared this intel with them...)

 

[puntloos]

3 hours ago, joth said:

One thing I'd mention is with a basement this is actually a 3-4 story house, replacing a 2 story one, on a larger footprint. So long as you follow all the rules the planners can't object, but it's likely to get some attention from neighbours and in particular any disgruntled folks in the area that had their own similar scale project rejected. If any of these manage to get it called in for debate, and the conservative (with both small and big c) councilors start crawling over it, then that's when it can get more stressful. Afaict their pet hates are McMansions, and apartment conversions with insufficient parking spaces. 

 

Eh I'm fine then my design is a Mansion King, I'll have you know.

 

But it's a fair point, although when it comes to the "2 extra floors" - both would be "small rooms" not a "full footprint". Perhaps it depends on how it's presented, but if I can represent the basment for what it's actually intended for - a "plant room", and the loft as indeed an undeveloped loft, perhaps that would help. (and it is factual too - core reason for the basmenent is indeed storing plant stuff, and core reason for loft is storage, and perhaps some play space for the kid, but no proper living.

 

 

[Bitpipe]

We had a similar challenge - first planning app rejected and one of the reasons was the ridge height exceeding the previous dwelling.

 

Our planning solution was to have ground floor at 2400mm, first floor at 2300mm and make the best of the room in roof space, which was 2330mm.

 

When we got the detailed drawings from MBC, we were still 100mm off as the floor decks were thicker than anticipated. We solved that by just going 100mm further down with the basement / foundation - the limits there were governed by getting the necessary foul drops from the downstairs loo to the street sewer - lots of calculations on the invert levels for each IC but we made it ok.

 

Could have tried to get away with it but decided not worth the risk.

 

Was worried that @2400mm the GF ceiling would feel too low but it's fine - as its all open plan and lots of floor to ceiling windows, it's never bothered us.

 

 

 

Just to add, as we're effectively a 4 story house (basement, GF, FF, RIR), every door that opens onto the hall / stairway from a habitable room (i.e. excluding bathrooms) is FD30 rated with fire strip. We have a nice glazed 926mm door into the GF hallway and it got very expensive as the glass needs to be FD30 also. We did not need to use fire rated PB (pink) as standard 12.5mm with a skim is considered to give 30min protection.

 

Basement also needed independent means of exit so there is a separate door there that opens to stairs up to ground level.

Edited July 19, 2020 by Bitpipe

[Bitpipe]

2 hours ago, puntloos said:

 

Eh I'm fine then my design is a Mansion King, I'll have you know.

 

But it's a fair point, although when it comes to the "2 extra floors" - both would be "small rooms" not a "full footprint". Perhaps it depends on how it's presented, but if I can represent the basment for what it's actually intended for - a "plant room", and the loft as indeed an undeveloped loft, perhaps that would help. (and it is factual too - core reason for the basmenent is indeed storing plant stuff, and core reason for loft is storage, and perhaps some play space for the kid, but no proper living.

 

Fire regs are one thing I'd never skimp on to get round BR.

 

It's your life you're playing with if anything goes wrong - they are written that way for a reason.

[puntloos]

21 hours ago, Mr Punter said:

Often eaves height is more of a target than ridge height.

That's it, I'm building a Church.

 

It is an interesting point, but I think in my case 'ridge height' is better for my case. (difference in eaves height is worse)

 

How do LPAs look up ridge heights and compare them? Case in point:

Ridge height of neighbour 1: 58.90 (above sea level)

My intended ridge height: 58.54 

 

Fine, right? But no, sadly my neighbours DPC is at 50.84 and mine - in the current house, 50.29. The 'absolute height' of that neighbour is 8.06m (vs my 8.25)

Dumb question but is there anything stopping me from sinking the house (or more specifically the DPC) a few cm?

 

 

 

 

[puntloos]

20 minutes ago, Bitpipe said:

 

Fire regs are one thing I'd never skimp on to get round BR.

It's your life you're playing with if anything goes wrong - they are written that way for a reason.

I think I'm missing one step of reasoning here. Which part of my 'ruminations' would imply I'm skimping on fire reqs? Maybe I misused 'small footprint' - I just meant that the full house footprint is maybe 125m2 where the basement is 25 and loft perhaps similar.

 

[Bitpipe]

1 hour ago, puntloos said:

Fine, right? But no, sadly my neighbours DPC is at 50.84 and mine - in the current house, 50.29. The 'absolute height' of that neighbour is 8.06m (vs my 8.25)

Dumb question but is there anything stopping me from sinking the house (or more specifically the DPC) a few cm?

 

Nope, its what we did, dropped the GF level by 100mm - just need to make sure that you don't compromise your invert levels to main sewer.

 

Re fire regs - if you're planning to make your loft at all habitable at completion - occasional play space etc, then you need to make sure that you're good on the fire regs - that's all.

 

You may consider a particular space as 100% non habitable and use it for some domestic purpose, even occasionally. You don't need to be sleeping overnight in it for it to count. Only bathrooms and hall cupboards were exempt from our FD30 regulation.

 

If the house is signed off and the loft is not considered a room, then you may be ok as any future change of use would be considered as a conversion under PD.

 

However if you build the loft as a room in roof from the outset then BR will probably be all over it.

[puntloos]

17 minutes ago, Bitpipe said:

 

Nope, its what we did, dropped the GF level by 100mm - just need to make sure that you don't compromise your invert levels to main sewer.

 

I guess my main question is: can I provide the info the LPA works with - e.g. can I put in my DAS that our ridge is planned to be 50.65 whereas neighbours are 50.55 and 50.89 respectively (which is also reflected on our survey) - or do they do their own due diligence, which might turn up the more contentious point of view, that we are aiming for 8.25m from DPC, where neighbours are 7.95 and 8.05 respectively. 

 

Who gets to "provide the data" the LPA uses

 

17 minutes ago, Bitpipe said:

Re fire regs - if you're planning to make your loft at all habitable at completion - occasional play space etc, then you need to make sure that you're good on the fire regs - that's all.

 

You may consider a particular space as 100% non habitable and use it for some domestic purpose, even occasionally. You don't need to be sleeping overnight in it for it to count. Only bathrooms and hall cupboards were exempt from our FD30 regulation.

 

 

If the house is signed off and the loft is not considered a room, then you may be ok as any future change of use would be considered as a conversion under PD.

However if you build the loft as a room in roof from the outset then BR will probably be all over it.

 

So that's the key part, and I have a similar  question as above: 

 

Who decides if it's a loft or a room? (and based on what)

 

A few people already suggested a few things:

 

8 hours ago, DevilDamo said:

Just don’t indicate any rooflights or dormers to the roof planes along with not providing them with a second floor plan. As and when you come to order the attic trusses, make sure there are allowances for double/triple trusses for any future openings.

 

8 hours ago, ProDave said:

Just don't mention the loft, you don't even need to tell them you are using attic trusses, that's only building control need to know that.  Just show "loft" on the plans with just a loft hatch as access.

 

So basically.. I'm thinking, of:

- Not even mentioning the loft

- Hatch, not my fancy spiral staircase.

- No rooflights, but plan for them with trusses etc when the time comes

- Make sure FD30 style doors can be fit in the right locations

 

 

Does that sound like it could work?

 

[puntloos]

1 hour ago, puntloos said:

Does that sound like it could work?

 

And as a bonus, surely I'd have to specify the basement? Or can I leave that out for planning permission?

 

 

 

 

 

[PeterW]

1 hour ago, puntloos said:

 

And as a bonus, surely I'd have to specify the basement? Or can I leave that out for planning permission?

Not a chance !! Basements require planning as they are an engineering activity. They also require escape windows / wells which show up on plans anyway. 

[DevilDamo]

@puntloos With all the various posts in relation to layouts, regulations, processes, etc... what exactly is your architect doing or advising upon? The majority, if not all of these this would normally be dealt with by them. Are they literally just a draughts(wo)man and have been instructed/paid as such?

Edited July 19, 2020 by DevilDamo

[puntloos]

3 minutes ago, DevilDamo said:

@puntloos With all the various posts in relation to layouts, regulations, processes, etc... what exactly is your architect doing or advising upon? The majority, if not all of these this would normally be dealt with by them. Are they literally just a draughts(wo)man and have been instructed/paid as such?

 

Do you mean my various posts across this forum? Or just here?

 

We're pretty happy with the skill of the Architect to design something 'elegant' but these type of details seem to not rank highly in their mind. (frankly, they're a bit of a luxury architect that tend to deal with 5000sqm mansions, while I'm trying to be really optimal in space saving)

 

So indeed I'm doing a bunch of legwork to squeeze the most out of the design myself. 

 

(plus they charge by the hour )

[DevilDamo]

Across the forum in general.

 

Even if somebody has been instructed to design something ‘elegantly’, they should also be aware and advise their client of the Planning and Building Regulation implications. It just doesn’t seem you’re getting that at all and I’d be questioning their capability. I assume you have learnt things here that you have not been told or heard before?

[puntloos]

21 minutes ago, DevilDamo said:

Across the forum in general.

 

Even if somebody has been instructed to design something ‘elegantly’, they should also be aware and advise their client of the Planning and Building Regulation implications. It just doesn’t seem you’re getting that at all and I’d be questioning their capability. I assume you have learnt things here that you have not been told or heard before?

I see your point, but nah it's not that bad, basically the exchange with them is mostly "here's the new design with the changes you requested implemented. We did it this way for reasons x,y,z. - and then I would go off and examine the details and figure out if perhaps I could push things further without running into worrying safety margins, and then repeat. 

 

Perhaps in retrospect it would fit my 'character' better if they would already give 3 options with pros and cons, but I just have the sense most people don't go into the level of detail and 'playing with options' that I do. (present company accepted of course, but I think this forum is unusually 'savy')

 

In this particular (loft or not) case, they recommend against building a 2200mm loft because they feel the LPA would shoot it down, which seems like a valid concern, but my current sense after this discussion is we could actually get more out of it and still get it passed..

Edited July 19, 2020 by puntloos

[dpmiller]

10 hours ago, PeterW said:

Not a chance !! Basements require planning as they are an engineering activity. They also require escape windows / wells which show up on plans anyway. 

 

Architect appears not to have considered this?

[puntloos]

4 hours ago, dpmiller said:

 

Architect appears not to have considered this?

 

I did wonder about that one, but I thought that if the basement contains no official living space (just a plant room and some storage) it was okay to go without?

[Bitpipe]

Here's your challenge.

 

Planners deal with planning law.  Building Control (whether LA or private) deal with adherence with building regs law. SEs ensure the dwelling will be structurally sound (and their work/calcs feeds into BC), QS will give you an estimate of what the dwelling could cost to build based on SPONs etc...

• Planners will happily give you permission to build a dwelling that fails to meet building regs. They will even give you planning permission for a building on land you don't own as that's a legal issue, not a planning issue (see also covenants etc..).
• Building control will happily tell you why the building you have planning for does not meet regs for a dozen or so reasons and needs modifications (e.g. extra insulation in roofs / walls, windows needing moved, fire provisions not being met, disability access etc..)
• SEs will happily tell you why the architects design is not buildable or that you need lots of steel to make it viable.
• QS will happily quote you a number you can't afford or one that you can afford but can't find a builder who will do it for that price.

One of your architect's roles should be to straddle these domains and design you a dwelling that will get planning, will pass building control and is buildable to your budget.  There may be some esoteric issues that they are not super familiar with which you can query them on but significant issues like fire regs etc should be familiar to them. At a min they should be all over the building regs, QS and SEs are usually outsourced (and may be provided by your builder / contractor). 

 

If they really are not engaging with you on these things then you need to be very wary as you may pay them handsomely and then pay again to have it all redesigned to keep SE, BC and even QS happy.

 

Regarding basement, yes planners do need to be aware as they impact the gross internal area which is a planning consideration. If there are street side visible elements like light wells then that factors in also.

 

Note if your basement is a dark windowless hole at the centre of your house with no independent means of exit then you could have issues depending on other fire suppression methods (sprinklers, FDs etc). Whatever you plan to use it for, if it has stairs down to it then BC will be interested.  i.e. if you're down there storing something when a fire starts and can't get out then you may die. That tends to get BCs attention.

 

A loft that could be converted to habitable use in the future but is just a windowless space with a hatch upon completion is probably not going to get attention as you would need to get permission to convert it in the future and would need to get BC to sign off any future works.

 

[puntloos]

6 hours ago, Bitpipe said:

Here's your challenge.

 

Planners deal with planning law.  Building Control (whether LA or private) deal with adherence with building regs law. SEs ensure the dwelling will be structurally sound (and their work/calcs feeds into BC), QS will give you an estimate of what the dwelling could cost to build based on SPONs etc...

• Planners will happily give you permission to build a dwelling that fails to meet building regs. They will even give you planning permission for a building on land you don't own as that's a legal issue, not a planning issue (see also covenants etc..).
• Building control will happily tell you why the building you have planning for does not meet regs for a dozen or so reasons and needs modifications (e.g. extra insulation in roofs / walls, windows needing moved, fire provisions not being met, disability access etc..)
• SEs will happily tell you why the architects design is not buildable or that you need lots of steel to make it viable.
• QS will happily quote you a number you can't afford or one that you can afford but can't find a builder who will do it for that price.

One of your architect's roles should be to straddle these domains and design you a dwelling that will get planning, will pass building control and is buildable to your budget.  There may be some esoteric issues that they are not super familiar with which you can query them on but significant issues like fire regs etc should be familiar to them. At a min they should be all over the building regs, QS and SEs are usually outsourced (and may be provided by your builder / contractor). 

 

If they really are not engaging with you on these things then you need to be very wary as you may pay them handsomely and then pay again to have it all redesigned to keep SE, BC and even QS happy.

 

Thanks, it's good to sanity check but my current impression is that the architect is delivering 'sound' designs, just that my approach to suggesting changes is to basically be the stupid layman and just randomly add some space here or move something there that 'seems better' with little heed to regulations.

 

Then the architect has to go in and 'solidify' things again. And because we're paying them I typically figure I ask here first

 

Sorry if some of my questions seem like my architect is dropping the ball but really I think it's mostly my ignorance and trying to learn!

 

6 hours ago, Bitpipe said:

Regarding basement, yes planners do need to be aware as they impact the gross internal area which is a planning consideration. If there are street side visible elements like light wells then that factors in also.

 

Fair.

 

6 hours ago, Bitpipe said:

Note if your basement is a dark windowless hole at the centre of your house with no independent means of exit then you could have issues depending on other fire suppression methods (sprinklers, FDs etc). Whatever you plan to use it for, if it has stairs down to it then BC will be interested.  i.e. if you're down there storing something when a fire starts and can't get out then you may die. That tends to get BCs attention.

Good to know

 

6 hours ago, Bitpipe said:

A loft that could be converted to habitable use in the future but is just a windowless space with a hatch upon completion is probably not going to get attention as you would need to get permission to convert it in the future and would need to get BC to sign off any future works.

 

 

FWIW this is the current architect design:

(the 400mm floor structure was based on advice from our builder as a safe amount, but can probably be squeezed, the central hall is up to the roof, so the actual loft in this pic is the left+right section)

 

As such, I don't think I can 'stretch' the loft to 2200.

 

Loft is currently 1800. 

I could probably get away with 2650/2350 for 1st and 2nd

-> 1900

Possibly 350mm floor structure depth (x3)

-> 2050

 

But that last 150 I don't really see where I can get that, unless I perhaps 'sink the house' 150..

 

[Bitpipe]

17 minutes ago, puntloos said:

 

Thanks, it's good to sanity check but my current impression is that the architect is delivering 'sound' designs, just that my approach to suggesting changes is to basically be the stupid layman and just randomly add some space here or move something there that 'seems better' with little heed to regulations.

 

Then the architect has to go in and 'solidify' things again. And because we're paying them I typically figure I ask here first

 

Sorry if some of my questions seem like my architect is dropping the ball but really I think it's mostly my ignorance and trying to learn!

 

 

Fair.

 

Good to know

 

 

FWIW this is the current architect design:

(the 400mm floor structure was based on advice from our builder as a safe amount, but can probably be squeezed, the central hall is up to the roof, so the actual loft in this pic is the left+right section)

 

As such, I don't think I can 'stretch' the loft to 2200.

 

Loft is currently 1800. 

I could probably get away with 2650/2350 for 1st and 2nd

-> 1900

Possibly 350mm floor structure depth (x3)

-> 2050

 

But that last 150 I don't really see where I can get that, unless I perhaps 'sink the house' 150..

 

 

Would you consider reducing your GF ceiling height?  Going above 2.4m incurs additional cost when it comes to plaster boarding  as the sheets come in 2.4m so lots of cuts? High ceilings are always impressive but it could be a compromise worth considering to make another floor viable.

 

For floor buildup, you need to allow 15mm for pb & skim on the ceiling underside and whatever your floor covering is upstairs. The floor deck is likely 18mm OSB so the rest is joist. Rule here is that the longer the span the deeper the joist to provide stiffness. The other consideration is any steel that you have in your roof structure to create large open span areas - these will be as deep as the engineer dictates (same principal as joists) and will need to be battened underneath to allow PB to be fixed to them.400mm is decent allowance - mine are 340mm surface to surface.

 

Do you know your sewage invert levels (if you're connecting to a mains sewer)? You work backwards from here to get the necessary fall (between 1:40 and 1:80) and then see if you're high enough for the ground floor drains to gravity flow to the main sewer.

 

If invert levels allow, your house can sit lower than the surrounding ground but you'll need a landscaping / drainage strategy like ACOs around the perimeter to intercept ground water. We have an imperceptible slope up from the house to the street boundary - did not need ACOs as the basement perimeter backfill acts as a giant French drain and also used a water permeable resin bound gravel/tarmac driveway.

 

One more consideration for that basement, what's your drainage strategy for it? If you're putting services or plant down there then you'll need some arrangement to extract water - e.g. the UVC tundish or MVHR/boiler condensate. Worse, if you had a flood (burst pipe, washing machine disaster etc) that's where the water may end up.

 

 

 

[the_r_sole]

as per @Bitpipe's post - it doesn't really feel like you're getting the most/best out of your architect because you're trying to drive the design - I'm sure any creatives in the group will have seen the I design, you watch pricelist before....

 

I've worked with a fair number of self builders before, but I've never have someone work like you appear to be, I'm not sure how or why you've engaged them, but it looks like you're paying money to a design professional and then redesigning their design - can you not just sit down around a table with a set of drawings and tell them what you want them to design?

 

[DevilDamo]

It’s all very well having a client wanting to get involved but to me, this much involvement is quite concerning. I’d feel embarrassed or upset if one of my clients was asking the quantity and quality of the OP across the forum. Just hope their architect never reads BH ?

[dpmiller]

maybe he/she does...

[the_r_sole]

12 minutes ago, dpmiller said:

maybe he/she does...

 

the next revision will be interesting then! ?

[puntloos]

1 hour ago, Bitpipe said:

Would you consider reducing your GF ceiling height?  Going above 2.4m incurs additional cost when it comes to plaster boarding  as the sheets come in 2.4m so lots of cuts? High ceilings are always impressive but it could be a compromise worth considering to make another floor viable.

 

Not for us, one of the primary reasons for a new build is that we want high(ish) ceilings. I actually intended to start another topic on this  (what is a good 'ratio' for height vs width vs depth of a room to not make it feel tunnel-y or tight.)

 

But handwavingly, I'm tall enough that without any 'stretching' I can touch a 2m40 ceiling, so no. But 2650+ would be great, 2600 probably acceptable. 

 

1 hour ago, Bitpipe said:

For floor buildup, you need to allow 15mm for pb & skim on the ceiling underside and whatever your floor covering is upstairs. The floor deck is likely 18mm OSB so the rest is joist. Rule here is that the longer the span the deeper the joist to provide stiffness. The other consideration is any steel that you have in your roof structure to create large open span areas - these will be as deep as the engineer dictates (same principal as joists) and will need to be battened underneath to allow PB to be fixed to them.400mm is decent allowance - mine are 340mm surface to surface.

 

What's the widest span you had to cover? (I understand there's a ton more variables, but just curious)

 

1 hour ago, Bitpipe said:

Do you know your sewage invert levels (if you're connecting to a mains sewer)? You work backwards from here to get the necessary fall (between 1:40 and 1:80) and then see if you're high enough for the ground floor drains to gravity flow to the main sewer.

 

Nope, don't know. I've been trying to find the info on my survey but I don't think it says. The only thing I see on there is a manhole marked "SV" (sewage valve?) about 20m away from the edge of my property, which is about 0.5m lower than my DPC, which sounds mildly promising since it would mean that it sits indeed at slightly better than about 1:50 ratio (assuming the actual pipe is somewhat below that manhole lid)

 

1 hour ago, Bitpipe said:

 

If invert levels allow, your house can sit lower than the surrounding ground but you'll need a landscaping / drainage strategy like ACOs around the perimeter to intercept ground water. We have an imperceptible slope up from the house to the street boundary - did not need ACOs as the basement perimeter backfill acts as a giant French drain and also used a water permeable resin bound gravel/tarmac driveway.

 

Doesn't sound like a massive deal then? 

 

As it stands my current DPC is 300mm above the street level (at the lowest point, toward the manhole), and the house is on a very slight upward slope (higher toward the garden)

(sorry for the colors, not my choice, but MH in green far left, SV slightly beyond that. 

 

 

1 hour ago, Bitpipe said:

 

One more consideration for that basement, what's your drainage strategy for it? If you're putting services or plant down there then you'll need some arrangement to extract water - e.g. the UVC tundish or MVHR/boiler condensate. Worse, if you had a flood (burst pipe, washing machine disaster etc) that's where the water may end up.

 

 

Yeah I'm sure some strategy will be done there, we haven't done detail design yet..

 

 

[DevilDamo]

SV would normally dictate a Stop Valve. Topographical surveys would usually include a key for the various abbreviations.