How do I solve this roofing pitch problem ?

[gavman99]

We're planning an extension to our home that will be approx 4m deep. We'd like a sloped roof but we don't think we'd have enough of an angle on the roof to meet any rainwater requirements. This is because the vertical height difference between the low and high point of roof is approx 1.1m giving us an angle of just over 15 degrees (the high point is just under a bedroom window so can't go any higher). I know you can get some roof tiles that will give you rain drainage at that angle but I suspect not if we want to match our existing tiles. I don't know what they are called but its a 3 year old Barratt house with red "wavy" double tiles so pretty bog standard stuff I reckon.

So my question is how can we have a sloped roof without giving away any depth to the extension ?

Could we combine a pitched roof at the minimum angle we need, with a small flat roof section for the rest ? If so, would you recommed the flat roof at the high point or the low point ?

Are there any other options ?

Hope that makes sense.
Thanks.

 

[freddiemercurystwin]

Theres always Decra http://www.decra.co.uk/Products.aspx or Marley Wessex http://www.marleyeternit.co.uk/Roofing/Concrete-Tiles/Wessex-Interlocking-Tile.aspx although they don't sound like they'll match your existing. Why not make it an interesting roof and use Zinc standing seam or similar? That's quite a contemporary look.

Or what about these http://www.sandtoft.com/tiles/our-products/concrete-range/pantile/double-pantile/product/ Trawl the web you'll probably find something. Confirmation of your existing tiles (or a photo) would save us wasting time tbh.

 

[datarebal]

Your tile sounds like a Marley mendip or Redland grovebury both very commonly used.

your options are as I see it:
1/ change tile type to suit new pitch
2/ small flat roof area at head of slope
3/ and my favorite and used many times, a small lead flat roof area the width of your upstairs windows only. Sounds strange but if done properly it works and looks good.

 

[garyo]

What about having a double hip ended roof and then a gully beneath the upstairs window? Then you'll be able to have as much pitch on the roof as you like, subject to not spoiling the view out of the upstairs window.

Gary

 

[gavman99]

Had to google it, but now that I've seen it, a hip ended roof sounds like a possibility.

What I didn't mention in the original post was that the plan is to have the ceiling right up to the height of the roof with a velux roof light. The aim here is to create a really bright open airy space.

Is it easy to build this style of roof with these roof height ceilings ? Can it be done without any of the roof support beams visible ?

Thanks.

 

[garyo]

I'm no roofing expert so I'll let someone else comment on the construction complexity. What you're describing is called a vaulted ceiling/roof, so that may help you with your googling.

These roofs tend to be fairly thick due to the insulation/strength requirements (no joist to form the base of the triangle), so you might want to consider how that would work with your low pitch, and make sure you're going to end up with the result that you want.

Gary

 

[JonB]

A neighbour of mine raised the level of the back bedroom window to give him a better slope.

 

[jono_h]

I built my extension with a 16 degree pitch and Marley Moderns, with no major problems in 4 years.

Use a quality roofing membrane, be generous with the the overlaps, and you'll probably be OK.

 

[gavman99]

See images below. This is a rough sketch of some of the options.

Option 1 is preferred but dont think we can get matching roof tiles for the low angle.

Option 2 involves going as far back as possible as the roof and then a steeper angle back down towards the wall. Is this combination of angles possible or difficult to do ?

Option 3 is the same angles with the high point in the middle.

Option 4 is probably my second favourite option. SImilar to option 2 but with a flat section to the wall.

I want this to be vaulted with a couple of velux roof windows so really hope this can be done.

 

[theoldun]

Looked at your post number of times, never got round to answering.
To work out run, rise and pitch answer couple questions, and will come back in two/three days with two solutions.
Need to know width of new build?
Width of window?
Height of window?
Height of bottom of window sill above first floor.
Position of window in relation to new build? Just give me a measure from the right hand flank wall of new build to the right hand side of window.
oldun

 

[lorreal]

Hello,
I am newbie in this forum site.
Like all roofing materials, the lower the roof pitch, the more suspect the roof is of leaking when it rains.The roof pitch is too low to cope with water that travels down the roof.
Thanks.

 

[gavman99]

Oldun,

The extension is actually a shared project involving me and my neighbour as we live in a semi detached house and we both figure it would be easier to build at the same time. Might be easier and save some costs that way.

See image below. The red lines are the outline of the planned extension. For clarity, I've shown the shared party walls in thicker lines.

- Length "A" is 6.88 metres. This width can't be changed. Has to be exactly this.

- Length "B" is 5 metres. This is the preferred depth although this could be changed to suit. Although we don't want to go much smaller to be honest.

- Length "C" is exactly 1 metre. This is the distance between the wall and the side of each upstairs window.

- Each upstairs window is 1.2 metres wide and 1.16 metres tall.

- The height from the ground to the window sill of the upstairs window is 3.5 metres.

Hope the above combined with the image makes sense.

We'd both like 2 velux roof windows, so that would be 4 windows in total.

Much appreciated. Thanks.

 

[theoldun]

First post you said 4m depth, now 5m depth. Think you will struggle to get planning on that depth back of semi Suggest you put the 5 metre question on planning and build regs. Some good lads on there, who will give you answer.
Did not answer critical question. Height of first floor window above first floor. Height of sill to ground is no good as do not know ground level relation to floor level
Never mind have taken chance. Have assumed window is 900mm above first floor and 3525 above DPC, 47 course. Think you have got depth of first floor window wrong. Will be either 1050 14 course, or 1200 16 course. All our figures are based on above.
As neighbour has joined in, easiest way now, pitch flank to flank and form gable back wall.
For all granular rolled tiles min pitch is 22.5 deg at 100mm headlap, for through coloured tiles min 17.5 deg at 100mm headlap.
Overall width 6880, divided by 2 = 3440 less 100mm outer skin, 100mm cavity. half of partition wall cav 50 = 3190 half span overall plate.
Ground floor storey height of 2400, and allowing for height of rafter above plate, you will just squeeze a 21deg pitch in and give you room for tile, batten and stepped flashing below the left hand bot corner of window sill.
To get to 22.5 deg pitch, drop storey height down to 2325, or to increase pitch further change first floor window to 1050 depth
If vaulting rafters, you want a top birds mouth below your top plumb cut to hang rafter on. We also put a 400/600mm flat at top to form small triangulation to stop any possible creep. You can also fix adjustable recessed ceiling lights in the flat part.
Use 50x150 for rafters @ 400 centres For U value of 0.20 use 150mm celotex FR4000, or for 0.18 use 165mm. To increase depth of rafters, gun one or two 25x50 battens to bottom of rafter.
You may have a few problems fire stopping at top but who ever draws your building regs will sort that out
For vaulted ceilings always consult SE.
If you do not want to do it this way, come back and will tell you another way.
oldun

 

[Woodi73]

Gavman99 did you ever get this problem sorted as I'm facing exactly the same issue? If you managed to get a good solution I would really appreciate hearing it.

 

[hardmetalking]

Just use zinc which can go down to 3 degrees pitch and is only 5kg per square metre.