Conservatories, Sunrooms - Your questions Answered
Difficult Sites / Building Works (18)

Please note: Most of the answers we feature here are from 1999 - early 2002. We endeavour to keep all links etc up to date, however if you spot any errors please let our webmaster know at It should also be noted that some replies may change in light of changes to legislation especially with regards to Planning Permission and Building Regulations. To submit a new question or to query an existing question visit http://www.ask-questions.com/yabbse/index.php.

This question answered by Mike Edwards at the DIYDOCTOR - The tool you are looking for is actually called a water level! It comes complete with hoses and gauges (about 50ft. of hose) Most big builders merchants will carry a tool catalogue which contains it.We got ours from Travis & Perkins for £26.00

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Question submitted by Sue

My conservatory is now completed. It has 2 dwarf walls to side and front and 1 full wall to side. The walls have been plastered and the floor screeded. I have noticed hairline cracks to the full wall and hairline cracks and small holes on the flooring. Our conservatory supplier have assured me that this is due to drying out quickly (some recent warm weather) and should not cause a problem in the future. Before I have the walls painted and the floor tiled I would appreciate your comments. Am I worrying unnecessarily?

This question is answered by the Conservatories Online editorial team - It is likely that the cracks are due to the drying out process. Screeded floors in particular will show cracks/small holes. For this reason you should always avoid walking on a "bare" screeded floor. A screeded floor is not like concrete and is relatively soft - this is why you put underlay/carpet or some other flooring finish on top. The benefits of a screed finish is that it allows you to have a flat/smooth floor level. If a screeded floor is particularly badly cracked, its possible to purchase "self leveling compounds" that will fill in the small holes/cracks. Who ever fits your tiles should be able to do this.

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Question submitted by Colin

I am planning a conservatory on a new house that is being built. One company has told me that the foundations must be a minimum of 3 feet deep yet another one said 18 inches. Which one is true?

This question is answered by the Conservatories Online editorial team - Depth of foundation depends on site conditions (type of soil). 18 inches is quite typical - however some companies will dig deeper as standard. These are just some of the differences between companies. Clearly the company digging deeper foundations will be doing more work and would we suspect be charging more. (Arguably they are also doing a better job) As most conservatories are not subject to building regulations - there are no statuary rulings on this. The links here http://www.conservatoriesonline.com/construct.htm and http://www.conservatoriesonline.com/construct1.htm should help

This question answered by Gary Paice BSc ARICS, Crownwood Conservatories, Woking - I believe the question needs addressing in three ways. 1. The effect the construction will have on the tree. 2. The effect the tree and its roots could have on the foundation work during construction. 3. Any possible post construction problems. All three of these issues will first be affected by the ground conditions. A heavy clay type soil will be far more susceptible to ground movement caused by variations in moisture content, and root damage. This is because water can make up a good deal of its volume at any given time. Sandy or gravel soils are less of a problem. Take good local advice on this. The tree in question is not a large tree of the type most given to problems. Its potential spread is less, and its root spread generally reflects this. If you are not building under the existing spread or canopy of a tree it is less of a problem. You are unlikely to damage the tree if you lie outside its spread, and may as a result not encounter its roots during construction. Conversely cutting through significant root growth can damage, and even kill the tree. Let us assume this is not the case. Foundations should always be constructed so that they extend below all vegetable soil (soil that contains matter likely to rot away in time especially if cut of from its source like tree roots) Provided in this instance the sides of the trench are examined and no fibrous roots are entering the trench then it should be fine. If roots do exist go down a further 225mm below the last of any such roots. It is an idea to perhaps extend the foundations on that side further than normal anyway. If roots were present in the side of the trench it would be good practice to mass fill the trench to give good root barrier protection. We do not want roots growing (or subsequently dying) under the building. Use a reinforced concrete slab to provide a fully supported slab, such as by using B785 steel mesh in 150mm of concrete supported all round. The NHBC provide a design guide for this. That way if there is any change in ground conditions it will not affect things. Using a 50mm "Jablite" polystyrene under the slab provides insulation, as well as a compressible layer to counter soil heave. If all of this is done, and foundations are constructed well, then there is not likely to be any danger to the tree or to the building after construction. Gary Paice BSc ARICS, Crownwood Conservatories, Woking http://www.crownwooddevelopments.co.uk

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Question submitted by Terry

I have had 3 quotes for a conservatory on a house of less than 2 years old. Although having since found your web site I may start again. None of these companies mentioned the possibility of a problem - but it has now been pointed out to me that I have "cavity tray outlets" on the wall where the conservatory is to be built, i.e. plastic inserts in the mortar between some of the bricks above the door lintel. Is it possible that these outlets will be a source of damp into the conservatory? If so is there any action I can take or tests I can make?

This question answered by the Conservatories Online editorial team - Cavity trays that "exit" into a conservatory can cause a problem with damp. We would recommend that new cavity trays are inserted just above the level of your conservatory roof. The exit points would then be above the conservatory roof level. This is especially important if you are considering plastering the house wall that will now be inside the conservatory. Even the smallest amount of damp will show up on plastered walls. The following links will explain the situation better. http://www.conservatoriesonline.com/topconstipsextra.htm and http://www.conservatoriesonline.com/construct3.htm

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Question submitted by Peter

I am having a 4mX3m conservatory constructed. What arrangements must be made for drainage of rainwater from the roof gutter? Are there any statutory requirements? I live in Crewe, England.

This question is answered by the Conservatories Online editorial team - Most conservatories are not subject to building regulation approval and as such there are no statutory standards. We would recommend that you have a soakaway constructed. (Basically a large 1 metre cubed hole in the ground filled with rubble) The soakaway should ideally be at least four metres away from your conservatory. Ask your builder / conservatory supplier for advise on constructing a soakaway. Some people drain into water butts but these do in our opinion fill up very quickly and are not really practical. You should not drain into your main drains (i.e. connect to manholes).

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Question submitted by Roy

I have a Victorian style conservatory to the rear of my house and would like a single storey extension to the front. It turns out that the existing foundations are some 12 feet deep because of the bad building land and a traditional extension would have to have piled foundations (as per the building inspector).

Would a conservatory style structure be able to cope with a "raft" or is piling inevitable ? ( the structure would become an extension of the dining room and used as sitting room at the front of the house).

This question answered by Gary Paice BSc ARICS, Crownwood Conservatories, Woking. - The question of foundation depths is a common one. The short answer is that in an ideal world the foundations should always be the same as the main structure to help eliminate the chance of differential movement. In a practical sense that is not always possible, nor dare I say necessary. But in this instance a piled foundation for a conservatory must be considered overkill. However you would need to dig an exploratory hole to ensure that the ground at least has some firmness. A raft or shallow strip foundation will do a job in supporting the conservatory although in both instances the introduction of a structural mesh reinforcement in the slab (say B785 mesh) would be good advice. Personally if I were going with a strip foundation I would take it down to what seems to be reasonably stable ground (hopefully perhaps 1 metre) and incorporate two 12mm steel reinforcing bars to the full perimeter, just to protect against a crack through the foundation itself. A 600mm minimum thickness of concrete would also be a recommendation. After that if the conservatory moves slightly at least it will move "as one unit", so be sure to not tooth in the brickwork, but leave facility for such slight movement. Local advice from a builder or installer to talk you through the detail of all of this would be best. All of this only applies of course if it is indeed a "Conservatory" as understood by the Building Inspector. Other than that you are in his hands, and probably into mini piling or a designed raft." Gary Paice BSc ARICS, Crownwood Conservatories, Woking

I would like to add a conservatory onto our kitchen. We have an "L" shaped house and the addition would have to be right in that inner 90 degree angle. Therefore, we have two roof pitches and low eaves to deal with. Is there any way we could successfully add a conservatory and NOT have disastrous leaks with all of the rain water coming from different directions and meeting in the same place? I hope I made myself clear in describing our dilemma. My husband seems to think that there is no way to work around it. I'm hoping the experts can tell me differently! Thanks so much!

This question answered by Chris Edwards of Classic Conservatories - For the purpose of a prompt answer and because of your comment of low eaves, we will presume your property is a ranch style. There are, in fact, two solutions to your dilemma, one being more desirable than the other. The first would include building a cricket or small dormer for the conservatory to butt against at the back, and, use a parallel box gutter running between the property roof and conservatory roof. This will allow water from the valley created to drain away in a manner that would avoid water retention adjacent to the foundation of the property. Alternatively where there is an eave overhang on both of the interior facets of an "L" shaped building. You could construct a square ended conservatory with a parallel box gutter which is "L" shaped to match the building. On the short side at the back of the conservatory the hip would be reversed so the water draining from the conservatory and property roof would be diverted to avoid water retention adjacent to the foundation of the property.

Please tell me what the best PVC product is i.e. should it be reinforced with steel or aluminium? Any tips would be helpful.

I was also told that the foundations needed to 'rest' for about 10 weeks before adding frame etc. Is this correct? Another supplier said the job could be completed in 3-5 days.

This Question answered by Tina Dunlop - In my opinion - there is really not much to choose between Galvanised Steel Reinforcement or Aluminium Reinforcement. Both do the job and leading companies uses both alternatives. What I do find is that "salespeople" will often make exaggerated claims one way or the other in an attempt to sell their product. Typically the arguments go as follows - Steel is stronger - but more likely to rust if the galvanisation is removed and Aluminium is not quite so strong - but will not rust! (That's the simplified arguments!) As an example of the "exaggeration" that can go on - I have know of companies to show photos of windows with rust coming from them! What is not explained is that when screws are inserted into galvanised steel is that a small amount of "swarf" is removed and with that the galvanisation. It's possible for the swarf - which will always drop down to the bottom of the frame to "rust". The evidence of this quickly disappears as the swarf oxidises. This rusting is "not catching" and will not pass to the rest of the reinforcing. Sorry if my answer is not "conclusive" - but I feel the more important consideration is the overall calibre of the company you chose and the quality/looks of the PVCu system - not whether Steel or Aluminium is used for reinforcement. The only other question I would raise with a supplier is "if the frames are fully reinforced"? - In my opinion they should be. Some suppliers will use terms such as "reinforced where necessary" - this is clearly not the same as "fully reinforced". With regards to a "rest" period between the base going down and conservatory being erected - seven working days is usually considered fine. Imagine what would happen to the building industry if you had to wait 10 weeks for base/walls to rest before going on with the rest of the building!

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Question submitted by Darryl

Where can we find 45 degree preformed bricks for our conservatory design?

This Question answered by Tina Dunlop - Most Builders Merchants will be able to help you with this. Only "problem" I find is that different merchants may refer to these bricks in different terms. For instance some will refer to them as ....... "Squints" "135 degree bricks" "Dog Legs" and "specials" Try Travis Perkins at http://www.travisperkins.co.uk Also Jewson at http://www.jewson.co.uk/ Some times its difficult to get the "angled" brick as an exact match to the main brick you use. Then its often quite nice to use a "contrasting" brick - for a bit of variation. Its also possible to take a normal brick - have it "professionally" cut and then "glued" back together. I don't have a link for that - but you may find that the Builders Merchants could make some suggestions.

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Question submitted by Jean

I am interested in a lean to across the back of my property (a semi). However it will sit on top of the main soil pipe from my property and also my kitchen waste pipes exit into a drain (that would fall inside the proposed lean-to). How do I cope with this?

This Question answered by Tina Dunlop - It's possible that some of what you want to do will require building regulation approval. (DRAINAGE!) You will find out more about this at the following "link"..... http://www.conservatoriesonline.com/planperm.htm Most leanto designs can be adapted to fit around a soil pipe. If the manhole will be inside the conservatory then you should use a doublesealed manhole cover. Most people rather than move soilpipe - "box it in" afterwards. With regards to the wastes - depending on the expense you wish to go to - you could........ 1. Reroute Wastes or 2. leave wastes where they are and "build" a gully cover (which is removable) over the drain. With this alternative you have to be aware that its possible in exceptional circumstances (usually when washing machine or similar is empting) that the flow of water into the drain may be so great that the water will spill over the drain cover. A variation on suggestion 2 is to seal gully over completely and fit a "rodding eye" so that if it is ever necessary - you can unblock drains etc. Opinions on the best method of coping with this - do vary - I am only giving you the most common solutions. I would suggest its best to ask your supplier for advise and as I said at the beginning you should enquire weather you need building regulation approval or not.

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Question submitted by Jean

I want to put a conservatory outside my kitchen where all the drains, water input, and sewage pipes are. Is this IMPOSSIBLE?

This Question answered by Tina Dunlop - Conservatories attached to kitchens are one of the most popular locations for conservatories. In order to "avoid" requiring Building regulation approval you should retain an external grade door between the Conservatory and Kitchen. Most conservatory companies can cope quite easily with the "difficulties" you describe. I think it best to get a number to tender and see what feedback they give you. For sure it is not impossible. I would in any case check out if there are any other circumstances (drainage etc) on your site which may require Building Regulation approval.

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Question submitted by Peter

I have a two story semi-detached Victorian house that overlooks the sea in Ventnor, Isle of Wight. The sea facing lounge and upper bedroom have a bay window. I am considering a conservatory. What is the best conservatory solution to fit the bay. I want a glass roof with a Victorian style gable.

This Question answered by Tina Dunlop - With a bit of imagination just about any style of conservatory can be fitted against (or around) a bay window. I have seen both lean-to and Victorian styles accommodated. Sure a lot more care will be required - especially with the sealing of the roof. Not every company will be interested in this project - but you will find there are companies who will be interested. Try and get them to show you photos of previous examples. The examples need not be "around" bays - just of difficult situations they have overcome in the past. A couple of points to remember..... 1. It is likely the conservatory roof will need to be constructed on site before final dimensions for the glass roof panels next to the bay can be calculated/measured. (This means it takes longer to complete the installation as typically toughened glass units take 7 - 10 days to make) 2. Allow for internal decoration around the bay afterwards - especially if existing bay is tile hung. I take it you would rather not look at tiles internally? I think some T/G style timber cladding can look good. To see some examples of a Victorian style conservatory fitting around a bay click here.

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Question submitted by Penny

We would like a two sided conservatory, however the shortest side wall that is currently in place is flat roofed and a strange shape!! We have a 5m run of back wall, complete with cast iron soil (stench) pipe!! The side wall has a 4 m run (flat roofed, height 2.8m). However the wall is not one continuous line. It has a sideways on "U" shaped area, like an inverted porch, to a depth of 0.7metres. What would happen about the roof taking the soil pipe and the above into consideration? I suspect this may be easy for you but it's causing me sleepless nights!!

This Question answered by Tina Dunlop - To answer the soil pipe question first. The most common solution is to "cut" the conservatory roof around the pipe and seal with "flash band" or similar. It is even possible to purchase special "two piece" flashing units, which join around the pipe to seal or alternatively have a lead-flashing piece welded together by a leadworker. (Leadworkers are usually plumbers - there are still a few left with this traditional skill) I would also replace the existing cast iron stench pipe in PVCu - as it will be easier to work with and seal against. If you are using some sort of pitched roof arrangement (say a hipped Edwardian Style with Box Gutter) then you have some additional difficulties - however the solution is basically the same. Specially fabricated box gutters to fit around Pipes can be fabricated. There are some other solutions but they would be much more difficult to describe in the context of this Q & A. I suggest you consult a conservatory specialist or if you are doing this yourself consult someone who specialises in making conservatory roofs. They will be able to advise you on box gutters etc. It is off course possible to move the soil pipe location - but this is usually not an option for most people. Most people "box around" the soil pipe below the roof level internally in order to disguise it. With regards to the "U" indent to the flat roof on the other side the most common solution is to extend the flat roof over the area of the "U" indent. Effectively you now no longer have the "U" indent but a straight edge, which you can fix directly against. As your height is 2.8 metres you will be best making the eaves height of the conservatory frames similar to this - otherwise you will have to insert an infill panel below the flat roof level. (At 2.8 metres you will have windows above your doors) You have given me a depth for the "U" bit but not a width. If it were reasonably wide then another solution would be to have a specially fabricated box gutter. Your question is a little bit more difficult than the usual ones I try to answer here. Due to the complications and the number of options available it really would be best to consult a specialist. I would not say it is easy to overcome - but there are certainly solutions. Most of the companies featured on this site should be able to help.

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Question submitted by Mark

At the rear of our house there are two inspection covers which not only serve our house but the other people in our close. The question is can we put a conservatory over these inspection covers and will we have to get planning permission to do so?

This Question answered by Tina Dunlop - Lots of people do place conservatories over inspection chambers (manholes) and therefore avoid moving them.  To do so - you will need to use double-sealed manhole covers. (To stop that smell!) You also need to realise that there may be occasions when either you are your neighbours will want to access the manhole. Whilst this may be rare you should be aware of this potential inconvenience. You will not need planning permission in England/Wales for this specific issue. However you will need Building Regulation approval if you decide to move the position of the inspection chamber. You may also need to check local Bylaws and restrictive covenants in your property deeds.

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Question submitted by Anna

I was wondering if you can build a conservatory on an existing deck. The deck is about 12 feet high. The house is a bi-level.  I have doors off the kitchen to the deck. If not do you have any other suggestions for the space.  I would like to enclose it and utilize for extra living space.

This Question answered by Tina Dunlop - As you live in the USA - I consulted Classic Conservatories. Here is their reply. Conservatories are designed for year round enjoyment. A conservatory can be built onto a deck which will need to be reinforced to building code. Your local building inspector will inspect the structure as part of the permit process. All work must be inspected whether you have a conservatory specialist or general contractor to build a room.

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Question submitted by Jac

I have a manhole cover where I would like to put the conservatory. Are they easily moved ? What cost am I looking at?

This Question answered by Tina Dunlop - It is quite possible to leave a manhole inside a conservatory (if it is not in the way of outside walls) - provided you use what is called a double sealed manhole cover. You need to decide if you can put up with the inconvenience of accessing the manhole (on those rare occasions) from inside your conservatory. Most people go with this option as its usually the easiest and cheapest. (My builder charged me I think less than £100 for a double sealed manhole cover). If a manhole must be moved then you will I believe need Building Regulations approval from your local council in England and Wales. Any competent builder should be able to organise this for you. Costs excluding the council fees will vary from £500 - £800. The costs would include re-routing drains and supplying materials. In my experience most builders do not "relish" this type of work and therefore costs are not usually very competitive even though in my opinion the job is not particularly difficult.

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Question submitted by Charles

I have found the conservatory I want - but all the quotes I get for doing the base/brickwork and installation  seem to vary greatly. Is there a "rough guide" to the rates one should pay for this?

This Question answered by Tina Dunlop - What you will pay will vary from region to region. I can only give a guide - but here goes. Concrete base inclusive of materials, labour and fitting a damp proof membrane - £94.00 per metre squared. Dwarf cavity walling inclusive - £105 per metre squared. So as an example a conservatory base measuring 4 metres by 4 metres with a 600 mm dwarf wall will cost £2,260.00. Most builders will charge you for the complete run of walling even though you will almost certainly have an opening for a door somewhere in the run. Also please be aware that most builders will have a minimum charge and smaller works will have higher rates. NOTE - this is only a guide - it is a fair guide to what a reputable / bona fide building contractor (who will guarantee their work) would charge. There will be many builders who will charge less - but likewise there will be some who will charge more. The above rates should include VAT in most instances. As a further guide I have seen rates as low as £70 per metre squared for bases and £75 per metre squared for walling. As always - best to shop around. Note, most builders will charge the same for both brick work or plastered/rendered walls inside. However, with plastered walling you will probably also want to plaster the existing house wall - and this will cost extra. There will be extra charges if your ground level needs to be built up to match internal house floor levels or if you have a particularly unusual brick to match. Also not included in above guide is moving drains or building soakaways. Rates for actually installing conservatories and sunrooms also vary - so here is another guide. A 3600 mm by 3600 mm Victorian style PVCu conservatory will cost approximately £800 to erect with a polycarbonate roof and £1050 to erect with a glass roof. A simple leanto - 4000 mm by 2700 mm will cost about £450 - £550 to install. Rates are generally higher for Hardwood conservatories. SPECIAL NOTE - Whilst most building contractors will be more than capable of doing your base etc - please be careful to employ an experienced conservatory and sunroom installer for the erection. Few builders have regular experience of installing conservatories and unless they have I would always opt for using a specialist installer. Most manufacturers and suppliers can recommend somebody for this. Best of the lot is if you can find a conservatory installer who will also do your base and walling. Remember all of the above is only a guide. However, I do hope it helps.