Self Build Extension Queries

Daragh86

Hi,

I have searched the forums but can't seem to find the answers I'm looking for, probably because they are pretty simple questions and don't belong here.

I am planning a extension to my house which comes in under 12sqm and other relivant planning regulations that exclude it from requiring planning permission. I am drawing up the plans at the moment and was going to prepare quite detailed construction drawings for pricing and throughout construction to keep myself in line.

My questions are:

Do I need to employe somebody to come to site periodically to check building standards? If so, is this a structural engineer, architect, ??? Any idea what the going rate is so a small, uncomplicated extension like this?

If I need an architect or structural engineer to sign off periodically on the build do I need to provide him/her with construction drawings before the build starts to approve them?


Also, I am having a problem at the moment with deciding what type of roof to construct. The extension is 4m long x 3m wide. The outside wall of the house will be centered in the rear wall of the house so there is a bedroom window directly above the centre of the width of the proposed extension. This presumably means I can't design a pitched roof? If not a pitched roof it will have to be a lean to design? If so what degree of angle should be used over an approx 4m span (or does it matter once there is a minium fall? If so what is the minimum?


Thanks for any help in advance.

martinn123

Daragh86 wrote: »

Hi,

I have searched the forums but can't seem to find the answers I'm looking for, probably because they are pretty simple questions and don't belong here.

I am planning a extension to my house which comes in under 12sqm and other relivant planning regulations that exclude it from requiring planning permission. I am drawing up the plans at the moment and was going to prepare quite detailed construction drawings for pricing and throughout construction to keep myself in line.

My questions are:

Do I need to employe somebody to come to site periodically to check building standards? If so, is this a structural engineer, architect, ??? Any idea what the going rate is so a small, uncomplicated extension like this?

If I need an architect or structural engineer to sign off periodically on the build do I need to provide him/her with construction drawings before the build starts to approve them?

In my opinion, if the extention is exempt from planning you should obtain a Cert that the building complies with Building Regulations, this can involve 3 visits, to examine foundations, insulation etc, again nearer completion, insulation DPC no drains covered up etc, and a final cert on completion. I have been quoted 200.00 per visit plus VAT, from a Surveyor, who has to carry Professional Indemnity Insurance, as the Cert will go with the deeds of your house and be examined should you sell.


Also, I am having a problem at the moment with deciding what type of roof to construct. The extension is 4m long x 3m wide. The outside wall of the house will be centered in the rear wall of the house so there is a bedroom window directly above the centre of the width of the proposed extension. This presumably means I can't design a pitched roof? If not a pitched roof it will have to be a lean to design? If so what degree of angle should be used over an approx 4m span (or does it matter once there is a minium fall? If so what is the minimum?


Thanks for any help in advance.

Not sure if this helps, but you could consider a Double Hipped Roof, that is sloping in 4 directions, from a central ridge, where it meets the house you will need a valley, for rain water

Poor Uncle Tom

Daragh86 wrote: »

I am planning a extension to my house which comes in under 12sqm and other relivant planning regulations that exclude it from requiring planning permission. I am drawing up the plans at the moment and was going to prepare quite detailed construction drawings for pricing and throughout construction to keep myself in line.

My questions are:

Do I need to employe somebody to come to site periodically to check building standards?

You don't need to, unless you are getting a mortgage and you need someone to sign off stage releases, but if you are not up on modern building methods you would be best advised to have someone look after the build for you.

Daragh86 wrote: »

If so, is this a structural engineer, architect, ???

An Indemnified Architectural Technician, Architect or Structural Engineer.

Daragh86 wrote: »

Any idea what the going rate is so a small, uncomplicated extension like this?

About €150 per stage inspection which should include sign off if needed.

Daragh86 wrote: »

If I need an architect or structural engineer to sign off periodically on the build do I need to provide him/her with construction drawings before the build starts to approve them?

Yes.

Daragh86 wrote: »

Also, I am having a problem at the moment with deciding what type of roof to construct. The extension is 4m long x 3m wide. The outside wall of the house will be centered in the rear wall of the house so there is a bedroom window directly above the centre of the width of the proposed extension. This presumably means I can't design a pitched roof?

If the GF to eaves height is 2.3m, the Floor to Ceiling height is 2.4m, the First Floor thickness is 225mm and the First Floor to Cill height in the first floor bedroom is 750mm. And also taking an overhang on the new roof of 300mm it should be possible to get 25 degrees for the new roof, but check this out first.

Daragh86 wrote: »

If not a pitched roof it will have to be a lean to design? If so what degree of angle should be used over an approx 4m span (or does it matter once there is a minium fall? If so what is the minimum?

It depends on the finished materials of the roof.

Mellor

martinn123 wrote: »

Not sure if this helps, but you could consider a Double Hipped Roof, that is sloping in 4 directions, from a central ridge, where it meets the house you will need a valley, for rain water

That would be a terrible idea. Draing towards the house is not good.

Op, you may be able to get a low pitched roof in, I wouldn't discount it just because of the window

Daragh86

Thanks very much for all the help lads.

Just another quick one Uncle Tom, if I don't get an architect/engineer in to sign off on the build will I have a problem in the future if I want to sell the house? Would I need a cert of compliance then?

Poor Uncle Tom

You may require a Certificate of Compliance with Building Regulations or a Certificate of Exemption from planning permission if you were selling. I would just check that out with your solicitor first to be safe.

(I said you may need them, but because the extension is so small these items may be overlooked, that's why it is best to check first)

Open A

Hi Daragh

The minimum pitch for a flat roof is 1 in 40. Modern flat roofs (if properly built) do not cause the same problems associated with flat roofs of the 1970s. Make sure the roof is 'warm deck', that is insulate over the roof structure creating a stable thermal environment for the rafters. Otherwise the roof will expand and contract causing problems to the weather-proof membrance.

There's lots of useful advice and tips on www.environ.ie including technical guidance documents (guides to compliance with building regulations), planning regulations, etc.

To be exempt from planning permission the maximum size of an extension is 40sq provided that the private open space (garden) remains at least 25sqm. This can vary from council to council (e.g. Wicklow) See http://www.environ.ie/en/Publications/DevelopmentandHousing/Planning/FileDownLoad,1586,en.pdf for more info on what you can do without planning permission.

I would always recommend talking to a professional. If you only need structural design advice then an engineer is probably more useful than an architect - pm me for suggestions (I'm not an engineer)

Good luck!

Claire

Daragh86

Thanks Claire. I'm going to get the design drawings done to as far as possible in the next week or so. I think I will have some bother with the roof design so I might give you a shout then if that's alright? Thanks very much for the help, it's much appreciated.

Mellor

Open A wrote: »

The minimum pitch for a flat roof is 1 in 40.

No it isn't.
The minimum pitch is totally dependant on the roof material.

To be exempt from planning permission the maximum size of an extension is 40sq provided that the private open space (garden) remains at least 25sqm. This can vary from council to council (e.g. Wicklow) See http://www.environ.ie/en/Publications/DevelopmentandHousing/Planning/FileDownLoad,1586,en.pdf for more info on what you can do without planning permission.

No it doesn't.
The planning act is a state act and applies everwhere. No council can override this.

Open A

Mellor, you're right, the pitch depend on materials. However to achieve sufficient fall in a flat roof 1in40 is the minimum pitch I would advise. You also need to be sure you use a suitable material for the roof's pitch

Wicklow County Council's Development Plan indicates plot ratios as low as 0.25, which in my experience, need to be maintained when building an extension. This doesn't contradict statute, a minimum of 25sqm must also be met, but most cases Wicklow Co. Co.'s rules work out stricter.

muffler

Open A wrote: »

Wicklow County Council's Development Plan indicates plot ratios as low as 0.25, which in my experience, need to be maintained when building an extension. This doesn't contradict statute, a minimum of 25sqm must also be met, but most cases Wicklow Co. Co.'s rules work out stricter.

Im not aware of the content of that devp. plan but it most likely applies to new builds where it is conditioned on the permission.

If the house has been erected for a period of time and there are no conditions regarding the reduction of the open space area in the rear garden then the 25m2 min. becomes the default area.

Open A

muffler wrote: »

Im not aware of the content of that devp. plan but it most likely applies to new builds where it is conditioned on the permission.

If the house has been erected for a period of time and there are no conditions regarding the reduction of the open space area in the rear garden then the 25m2 min. becomes the default area.

I recently applied for planning permission for an extension to a house in Wicklow on behalf of a client so I have some experience of this. Pm me if you'd like details.

archtech

Open A wrote: »

I recently applied for planning permission for an extension to a house in Wicklow on behalf of a client so I have some experience of this. Pm me if you'd like details.

The fact you applied for planning permission meant that the development didn't fall in the category of exempted development. In that case the planning authority has to(or is meant to) take into account the policies of the development plan, which may be stricter than or different to the requirements of the Planning and Development Acts/Regulations. However if a development satisfies the criteria for exempted development under the Planning and Development Acts/Regulations and doesn't need a planning application then the development plan is not applicable, and one only has to comply with the relevant legislation.

Open A

archtech wrote: »

The fact you applied for planning permission meant that the development didn't fall in the category of exempted development. In that case the planning authority has to(or is meant to) take into account the policies of the development plan, which may be stricter than or different to the requirements of the Planning and Development Acts/Regulations. However if a development satisfies the criteria for exempted development under the Planning and Development Acts/Regulations and doesn't need a planning application then the development plan is not applicable, and one only has to comply with the relevant legislation.

I stand corrected, good to know.

martinn123

Mellor wrote: »

That would be a terrible idea. Draing towards the house is not good.

Op, you may be able to get a low pitched roof in, I wouldn't discount it just because of the window

In your opinion ?

all the posts here seem to be recommending leanto, or nearly flat roofs, what about if he wants a velux type window, to let in some light, in my experience,even though they advertise as working as low as 15deg, in reality they leak at less than 20deg, not always but sometimes.

Poor Uncle Tom

martinn123 wrote: »

In your opinion ?

all the posts here seem to be recommending leanto, or nearly flat roofs, what about if he wants a velux type window, to let in some light, in my experience,even though they advertise as working as low as 15deg, in reality they leak at less than 20deg, not always but sometimes.

I think there are better solution options then choosing the option you outlined above. It isn't a good idea to direct rainfall towards the house wall if it can be avoided, and I believe it can be avoided here. Also from a design point a 'stand alone' hipped roof doesn't integrate very well as a building extension, however small it might be.

martinn123

Poor Uncle Tom wrote: »

If the GF to eaves height is 2.3m, the Floor to Ceiling height is 2.4m, the First Floor thickness is 225mm and the First Floor to Cill height in the first floor bedroom is 750mm. And also taking an overhang on the new roof of 300mm it should be possible to get 25 degrees for the new roof, but check this out first.


It depends on the finished materials of the roof.

This I agree with, and would allow a hipped roof, i.e inverted V where it attaches to house, however subsiquent posts seem to be towards a lean to, which in my opinion look poor, especially a low pitch.

My last post refers to light, as depending on where the extention comes off the house there may be a loss of light, unless there is a window in the gable end, if its a terraced house, or a semi, you can create a corridor, very dark leading to the extention, resulting in no additional net additional usable space

Mellor

martinn123 wrote: »

In your opinion ?

No not in my opinion. In the opinion of any one who is in anyway capable in detailing and water proofing.
Draining towards a valley abutting a wall is a bad idea. Ig the DP blocks, there could be serious issues.
IF this junction was needed, for whatever reason, then traditional techniques and materials wouldn't be used imo.

all the posts here seem to be recommending leanto, or nearly flat roofs,

All the posts didn't recommend flat or lean-to, in fact no post reccomended either. You suggested a double hip, and myself and UncleTom suggesting having a proper look at pitched. Open A answered the OP's question on angle of a flat roof, she didn't suggest any option though.

The other option, not mentioned would be monopitch, where the direction of fall is parallel to the rear wall. Some people might prefer this to a traditional lean to. I've seen some very good roofs like that, and were generally more "architectural" in design.
Personally, I don't like lean to roofs either, I prefer pitched and flat in that order before a lean to.

what about if he wants a velux type window, to let in some light, in my experience,even though they advertise as working as low as 15deg, in reality they leak at less than 20deg, not always but sometimes.

A velux is for pitched roofs. And would work perfectly with my suggestion of a regular pitched roof. I don't see how a double hip helps install a velux here.

Obviously a flat roof would require a flat roof light. This will let in as much light as a velux.

martinn123 wrote: »

This I agree with, and would allow a hipped roof, i.e inverted V where it attaches to house, however subsiquent posts seem to be towards a lean to, which in my opinion look poor, especially a low pitch.

My last post refers to light, as depending on where the extention comes off the house there may be a loss of light, unless there is a window in the gable end, if its a terraced house, or a semi, you can create a corridor, very dark leading to the extention, resulting in no additional net additional usable space

Who suggested a lean to?
The only person that mentioned a lean-to before now (other than the OP) was you?

If light is an issue, then the type of roof won't solve or change this.

martinn123

Mellor wrote: »

No not in my opinion. In the opinion of any one who is in anyway capable in detailing and water proofing.
Draining towards a valley abutting a wall is a bad idea. Ig the DP blocks, there could be serious issues.
IF this junction was needed, for whatever reason, then traditional techniques and materials wouldn't be used imo.


All the posts didn't recommend flat or lean-to, in fact no post reccomended either. You suggested a double hip, and myself and UncleTom suggesting having a proper look at pitched. Open A answered the OP's question on angle of a flat roof, she didn't suggest any option though.


Who suggested a lean to?
The only person that mentioned a lean-to before now (other than the OP) was you?

.

Sorry I don't know how to multi quote, but if you can follow this

OPEN A, Post 7 '' The Minimum pitch for a flat roof is 1 in 40. make sure the roof is warm deck ''

MELLOR Post 9. ''No it Isn't dependant on material''

OPEN A Post 10 '' to achieve sufficient fall in flat roof, 1 in 40 is the minimum pitch I would advise

Thats where the subject of lean to or flat roofs started, I am merely stating in my opinion they look poor.

as for light, a Velux either side of a double hip roof will provide light.

Open A

Daragh,

Something to think about is whether you mind if the highest point of the roof is higher than the window cill on the first floor. Personally, I think this looks terrible from the first floor window; it will probably block any view you have of your garden and may block light as well.

If you decide to keep your roof under first floor cill level, then a flat roof is the best way to mazimise height downstairs.

On the otherhand, you may decide that what you gain downstairs makes it worth having a roof with its highest point above window cill level on the first floor. In this instance I agree with the suggestions on the inverted v. I am assuming that the valley would run paralell to the house. If your extension is the full width of your plot you may want to consider other options and it could get tricky finding a long term solution to bringing the water from the valley away from the house.

martinn123 wrote: »

My last post refers to light, as depending on where the extention comes off the house there may be a loss of light, unless there is a window in the gable end, if its a terraced house, or a semi, you can create a corridor, very dark leading to the extention, resulting in no additional net additional usable space

I completely agree with this. In your design be clear about what the room / rooms in your house next to the extension will be used for and how they will be lit. I have been to houses where the extension has reduced usable space and created large dark areas in the centre of the plan. If you are in anyway unsure about this I recommend talking to an architect about figuring out the best use of house + extension.

Good luck!

martinn123

This is the type of roof I have in mind, while the width is larger than the OP mentioned you get the idea

Good Luck.

Open A

martinn123 wrote: »

This is the type of roof I have in mind, while the width is larger than the OP mentioned you get the idea

Good Luck.

Here is a flat roof option for a similar site. We built the extension at garden level which maximised the ceiling height inside and gives great connection to the garden.

All other things being equal I prefer a pitched roof, but sometimes a flat roof is the most practical answer.

Open A

Open A wrote: »

Here is a flat roof option for a similar site. We built the extension at garden level which maximised the ceiling height inside and gives great connection to the garden.

All other things being equal I prefer a pitched roof, but sometimes a flat roof is the most practical answer.

don't think my photos worked there, sorry about that!

finola75

I would personally consult an architect before doing anything. I have once met an architect I]snip[/I who works on famous projects in the UK who says an architect is important for the quality of the construction and material you are going to use. my current neighbors are renovating their house without the help of an architect and the building company is making a mess out of it and it is costing them a fortune to fix all the damage.


Mod edit: finola, I've edited out the name of the architect. There's no need to mention it (plus its against the rules).