How would this build meet regs???

[Footsoldier888]

This is the extension that was passed just a few days before I moved from my old house.

Putting aside the fact I was a bit cheesed off it got approved, as a project I found it very interesting and was sorry to miss it going up.

The primary question I have is about the roof construction because as you can see the roof space is vaulted. Do you think the roof is going to be a SIP roof??? The velux windows are 1.34m wide and 93.4cm deep. Or is it some form of steel construction? The length is 7.1m and 3.2 internal height. If so would there be a steel purlin going to the gable wall? They have allowed about 20cm in the roof for insulation, is that enough? Also the gap between first and second floor was 20cm.

As you can see the en-suite dimensions are pretty tight so I was wondering if there might be an impact with this space???

On the ground floor they are building a garden room and the plan is to build up from the existing line of the Sussex kitchen, with the glass in the Sussex being replaced as it sits on the bricks they would be building up from (see last photo).

I presume they would have to dig a trial hole to check foundations here. I was wondering how it works on the rest of the foundation line if the existing foundations were adequate but shallower than you would dig today. Also how does it work with the bricks and cavity width??? The dimension seems to be the same as today on the plan at 300 but it was built in the mid 1960's so were cavities really that big then??? Also was there insulation and what about the brick tie condition? I had the same Sussex next door and my brickwork was damp and frost damaged and theirs wasn't much better. Water would splash off the patio and hit them a lot and I think they should have used engineering bricks there really.

As I see it (only a novice though) is it really feasible to do this??? Or would you remove the brickwork and rebuild from block below ground say?

All comments appreciated thanks.

 

[freddiemercurystwin]

I don't see anything that would phase a competent designer.

 

[Footsoldier888]

Agreed - I was just wondering what people would typically opt for on the roof as I am not too clever on vaulted roofs .

Perhaps this thread would be better off in projects or building??? Wasn't sure if I could put it in building since it hasn't been built.

 

[^woody^]

A ridge beam comes to mind

 

[noseall]

In respect to the GF, the garage would likely be demolished, existing foundations dug out and all new foundation trenches dug and concreted. This would allow easy access for drainage etc along with a full thermal spec' floor.

 

[Footsoldier888]

A ridge beam comes to mind

Aha! So by tieing it to the gable wall does that mean purlins would not be needed?

How does it work having so few rafters what with the wide velux windows then???

This idea of the sloping and vaulted roof works so much better on a side extension I can't but wonder why it is not a lot more common. I see so many of the standard side extension but you end up with a low ceilinged rectangle that way. This way almost seems a bit too good to be true somehow.

 

[Footsoldier888]

In respect to the GF, the garage would likely be demolished, existing foundations dug out and all new foundation trenches dug and concreted. This would allow easy access for drainage etc along with a full thermal spec' floor.

Thanks - the garage is on a slab foundation so you are correct sir.

Regarding the foundations under the Sussex kitchen, if they are not sufficient then the kitchen floor would have to come out and there would be a big cost implication.

For a beginner like me I can see how a project such as this could result in unexpected costs if you don't get some really detailed drawings at the outset.

 

[^woody^]

A ridge beam comes to mind

Aha! So by tieing it to the gable wall does that mean purlins would not be needed?

How does it work having so few rafters what with the wide velux windows then???

This idea of the sloping and vaulted roof works so much better on a side extension I can't but wonder why it is not a lot more common. I see so many of the standard side extension but you end up with a low ceilinged rectangle that way. This way almost seems a bit too good to be true somehow.

A ridge beam just holds the top of the rafters up. That in turn prevents the roof spreading by preventing the rafters pivoting. It is not about tying to a gable wall. The gable wall supports the ridge beam, that's all.

Purlins have different function and are used to support rafters that are too thin to support a load on their own over their span. Like piers supporting a bridge.

I dont understand what you are referring to with veluxes and too few rafters.

Vaulted ceilings are not more common be cause many plan drawers are not competent enough to even think about them, let alone design them. But not everyone wants a high sloping ceiling anyway.

 

[Footsoldier888]

Still struggling here .

When you say ridge beam do you mean steel or wood??? If it's just holding the top of the rafters up why does it need to be steel???

Understand about the purlins now but what then is tying the gable wall in?

Can you beef up the rafters so as not to need purlins then???

Regarding the velux I was thinking there may be a limit as to how many rafters the window could span as the tend to be long and thinnish normally, that was all I was thinking.

Scary if what you say about plan drawers is true. I accept it's not for everyone but the big advantage is it gives you light on both ends of the room. Funnily enough the parish council objected to the frontage though saying it wasn't in keeping with the area - ie someone had a good idea finally .

 

[freddiemercurystwin]

A ridge beam can be steel or timber but at certain span steel becomes more practical. Rafters can span without purlins if they are adequate and can support large rooflights usually doubling up each side of the rooflight, sometimes tripling, the first floor is tieing the gable in not that it's gonna go anywhere.

WTF does the parish know about design? An uneducated and ill informed bunch of cretins that makes the planners look competent.

 

[wessex101]

WTF does the parish know about design? An uneducated and ill informed bunch of cretins that makes the planners look competent.

Amen to that.

I cannot understand the OP's surprise at this design, it looks quite ordinary really. It is quite common in a situation like this where the side extension is stepped back and the eaves are lowered to reduce "terracing". A lot of my designs have vaulted ceilings these day, they are very popular and often specifically requested by the client. In fact I'm working on one at the moment where we are ripping out a flat ceiling to an extension and creating a vaulted ceiling.

Mind you there do seem to be a lot of crap designers out there who churn out the same old boring box extensions so maybe good design and imaginative solutions are less common than I thought.

 

[Footsoldier888]

I am in a suburb of York and I haven't been able to find another one locally, infact the flat roofed side extension is still alive and kicking here! But so many have the 'in profile' roof with the lowish ceiling.

wessex have you used a SIP roof on one of these atall??? I was just wondering how these vaulted ones perform temperature wise. Like in my example the en-suite is exposed to a north wind blowing down the street and it's ahead of the street building line and above an unheated store. Also the bedroom has a large volume of space to heat. Then you can have the opposite effect in summer. I would imagine the quality of insulation used could make a big difference to the enjoyment of the space.

Still worrying about the gable here! In a traditional one you have lateral restraint straps tying the wall to the ceiling joists. So what does their job on the vaulted one??? Or do you have a much longer strap say???

wessex are you going purlins on yours???

 

[wessex101]

Personally I don't rate SIP's. You can usually achieve the same result using traditional building methods safe in the knowledge that it wont delaminate or degrade after 10 years and probably be cheaper. You can incorporate insulation up to Building Regulations standards for the same overall thickness as a SIP.

You obviously have to factor in the increase room volume for heating but with modern levels of insulation it isn't a problem.

For most residential projects the stability of the gable wall is not a problem. Not having straps at ceiling level really isn't that much of a problem unless you have a very tall gable in a very exposed position.

 

[Footsoldier888]

Interesting - SIP's always look the business on Grand Designs but then I have never seen them in real life. Or done any building for that matter.

 

[freddiemercurystwin]

SIP's are a developers dream and they have their place. But in the real world they don't lend themselves to domestic extensions.