Ideally, an alpine house should be located in an open, sunny position but if you don’t have this space, Lancashire Lad, then you will have to make do with what is available. As the chosen location is not 100% perfect then don’t go spending £1,000s on a purpose built alpine house! A bog-standard from B&Q will do just as well once you have customised it. Remember that the main purpose of an alpine house is to keep overhead rain off the crown of the plants but allow plenty of ventilation. Buy some extra side vents for this purpose. Try to orient the greenhouse so that the gable end opposite the door is on the least sunny side. When we built our latest one I didn’t put any glass in this wall but made simple wooden frames covered with fine mesh from the garden centre. I also have some similar panels in the door. This allows air to pass through at all times but restrict strong winds that could do damage. In the summer we also remove some panes of glass to increase the ventilation. If you have cats then the openings created are best covered with some netting to keep birds out – cats and birds in the alpine house at the same time is not a good idea! A solid floor, concrete or slabs, is probably better than a soft one. Alpines are usually displayed on a bench at waist height so the legs of this bench will need to sit on something. If you are going to include a sand plunge bed then this will be very heavy and need the firm floor to sit on.
Enjoy your alpine house!

My Alpines are still outside, covered with old sacks !

Some will survive like that Diane others wont - what are you planning on actually having in there Lancashire Lad?

I haven't decided what to grow just yet. I suppose the conditions may dictate that once it's up.

I thought I may build a structure out of breeze blocks and wood.
I thought of doing the base (3 foot high) in breeze blocks then put a wooden frame on top with glass.
The structure I thought of would be 8 foot by 6 foot so a bed either side at waist height resting on breeze blocks. So the beds would each be 8 foot by about 2 foot with a 2 foot path down the middle.
I wondered if I should put mesh on both ends with a door in the middle at each end. That hopefully should provide the ventilation. The walls and roof would be glass.
There's a 6 foot fence on either side so it's sheltered but I don't have anywhere else I'm afraid.

Ll, why are you asking on here??? :-)))) You already have an excellent idea of what you want and obviously think that you are capable of building it. Well done and good luck to you!
Now that I know your design plan I can say that your ventilation ideas should be pretty good but I would still try to add a few louvered vents along the side of the house.
You might want to consider a plunge bed on the brightest side and a flat bench on the other so that you can stand random pots on thios and also use it as a work table; a boon in poor weather.
Regarding the benches, you talk about the house being six feet wide so the benches and the walkway would be two feet - remember that the side walls of the benches have a thickness so you will lose out somewhere in the width.

Why bother with walls. My Alpine house has roof and walls up the half way, but nothing on the top half at all.
My Glass house for Alpines (different to an Alpine House has mesh doors at either end and that seems to be enough ventilation even for Primula allionii which is the devil for Botrytis in Winter.

See here for Plunge beds
http://www.growsonyou.com/Owdboggy/blog/18366-making-plunge-beds-in-the-glasshouse
and here for my Alpine House
http://www.growsonyou.com/Owdboggy/blog/18354-my-alpine-house

I would have thought Hywel's Cactus House an easier option, with the netting at the ends. He can walk round it.
I am lucky Moongrow - am surrounded by high protective fencing. The sacks soak up the wet the Alpines dont like, they get too big really. Never mind, cant have it all ways.

Many thanks for the replies, and the photos are truly inspirational.
Alpines are something that I have dabbled with for a few years and in the past I have attended slide shows at the East Lancs Alpine Society. I've also visited Holehird several times in the Lake District and their Alpine House is a joy.

Basically I would now like to get rid of my poly tunnel which I have used for veg and replace it with an Alpine House.
I have ideas as described above but am looking for reassurance that I am on the right tracks as I think this project will cost me a couple of hundred pounds at least. I don't want to buy another "greenhouse" if it's not the way to go and the advice I have received so far will certainly help me plan things better.

I would suggest that 'a couple of hundred pounds' would be a very conservative estimate for the greenhouse, Lancs, unless you have a source of cheap material. A wooden alpine house looks far superior to an aluminium one but it is high maintenance. Wood has a nasty tendancy to rot and you don't want the glass collapsing onto your precious plants, never mind yourself.
An alternative could be a cheap aluminium greenhouse lifted onto, say, an 18" block base.

If you go to the AGS East Lancs group then there are some very experienced growers there who would be able to give great advice. I know many of them and they are a grand group of folks.

You could also join the Scottish Rock Garden Club - take a look at their website www.srgc.net/ They hold joint shows with the AGS in Hexham, Newcastle and Blackpool.

Another idea is to look around locally, a lot of people want to get rid of greenhouses, if someone would dismantle and remove them. They advertise them on the cheap ads. pages or in shop windows. I know a man who has 'collected' about ten of them. Its become an obsession. Some he joined together to make a thirty foot long one on his allotment.
The money saved could be used for louvre glass, and other necessaries for the precious Alpines.

My idea now is to build the bottom 3 foot in breeze blocks. Then put a (treated) wooden frame on top of this with a sloping roof ( to make the joints easier). Then I will glaze the top of the front and back, plus the roof. The sides and doors I will cover in mesh.
The tip about the plunge bench on one side and a flat bench on the other seems the best way forward.
I reckon I can do that for a couple of hundred pounds (as long as I don't go to a super store for the materials).

Good luck LL let us know how you get on!

Take lots of photographs during construction. I would like to see a blog of what you do.

Thanks - I will do that. I'll probably need more advice as it progresses for a soil mix and plants etc - but I'll leave that one for now.