Garden Deck With Greenhouse

This is how we created our recently finished hardwood garden deck with greenhouse. We love using the house in the chilly evenings and when it rains. The deck is obviously great when the weather is good, and with trees providing nice shade.

The Plan

This is the blueprint of the deck. The size was determined by the amount of space we had available, and where the trees were placed. Support beams for the deck are 60cm apart. On each beam, there are four foundations supporting the beam. For the seven longer beams under the house, there is an additional foundation. Foundations are approximately 130cm apart along the beam.

The outer footprint of the greenhouse is 3.84x3.84m. For a detailed measurements see the link in the Bill Of Materials.

The left part of the deck is at level with the ground, and about 50cm above the ground in the right end. This gives a nice feeling of being integrated with the garden. The stairs are 120cm wide.

Preparation

Clearing bushes, removing an old shed with it's foundation, and levelling the ground. We left as many of the trees and bushes as we could, so we did not have to wait many years for everything to grow in.

In the pictures you can see four temporary wooden beams, that were levelled and had the height of the final deck and support beams. This way it was easy to see how much earth that had to be removed, as it is essential that the final beams are not in direct contact with the earth, which would cause them to quickly rot.

Concrete Footings

The foundation shoes were first temporarily bolted onto an inflexible fiberboard, and stuck into concrete four at a time. It can be seen seen supported in the front of the picture, by some temporary garden fence rods. The height does not have to be super precise, as the beams can be adjusted in the shoes later. Once the cement has set, the fiberboard is removed again. (instead of the fiberboard, you can use one of the beams. I just used the fiberboard because it was lighter)

Holes for the concrete were drilled with a ø10cm hand earth auger, to a depth of approximately 60cm. Shoes were placed 130cm apart.

I had a cement mixer at hand, but usually mixed the cement in a big bucket or wheel barrel, as I worked on it a few hours a day after work. And cleaning a cement mixer takes a lot of time and water.

To make sure you start out completely square, you can use the 3-4-5 trick. Place three rods with a distance of 3m, 4m and 5m apart, and place a string along the 3m and 4m side. These strings will be at a perfect 90° angle, you can use to align the support beams with. (it will of course also work with 6m, 8m and 10m etc., as long as you keep the 3:4:5 ratio)

Support Beams

When bolting the beams onto the shoes, you can adjust the height by placing wedges between the shoe and the beam, as illustrated in the sketch.

I started out by carefully levelling out every third or fourth beam, and then placed a long aluminium profile across, to get the height for the beams in between. This way you can save some time on levelling, Beams were placed 60cm apart, but this will depend on the wood and thickness of the planks you are using. A minimum of 60cm is recommended for 23x145mm Jatoba hardwood.

The support beams are 40x80mm, but I would recommend using at least 50mm wide beams, as the deck screws have to be placed very close the end of the plank, when they meet each other on a narrow beam.

Greenhouse Foundation

The greenhouse foundation is the black aluminium frame in the pictures, with posts in each corner set in cement. The foundation and frame is not attached to the deck, but hovers 5mm above the deck. My dog demonstrates how the foundation corner posts (and electricity) is passed through the deck.
The foundation was temporarely assembled and cast after the beams were in place, but before the deck was layed. This way the beams could be used as a refernce to get the foundation in the right height (plank height+5mm gap), and aligned with the deck.

The foundation was disassembled after the cement set (except for the posts) so that the deck could be layed. When the deck was complete, the 5mm gap between the foundation frame and the deck was closed with a silicone seal to allow for the deck to move underneath the house.

I did not know how much the boards would move with the seasons, or how a storm would affect the house, hence this slightly complicated solution, instead of just bolting the house to the deck. The foundation for the house was stronger than for the deck, and with reinforcement so that it can withstand a storm. Consult and follow the manual of your greenhouse.

There is outdoor wires for electricity drawn to two corners of the house, and attached to the side of the beams,

How to Cut the Planks

Before you start laying the deck, it is a good idea to plan how to cut the planks. Otherwise you could end up with all the joints in one location, or in a strange looking repetetive pattern.

The planks were 540cm long (half the length of the deck), each spanning nine beams 60cm apart. To spread out the joints, and making as few cuts as possible, I choose the layout in the sketch. Starting with two full length planks in the first row. Plank A was then cut so that it spanned two and seven beams, with a full plank between them, and so forth. The pattern repeated after seven planks.

(this is why it takes me forever to finish a project! :)

Laying the Deck

The deck was mounted with a 5mm gap. The supplier of the boards recommended 7mm, and I guess they were right :) The boards change a lot with humidity, and they were dry when I layed them out.

In the part of the deck that was inside the house, I placed an self adhesive rubber seal in the gaps, to reduce draft and bugs coming up from the underside.

It is important to use stainless steel screws certified for the type of hardwood you are going to use, otherwise they will discolor the wood. And remember that stainless screws are very soft, so you only get one chance putting them in. To make sure you always place the deck screws in the same distance from the edge, you can create a cardboard template, or 3D print one if you have too much time.

I used some clamps where you can replace the jaws with a deck jaw (see the image in BOM). This allowed for pulling and pushing the planks into place. I would recommend getting the biggest you can, as hardwood require some force to be kept in place.

There is a screw in the middle of both ends of the beams, between which the yellow string is attached, so that all screws could be aligned properly.

(I had originally planned to drain away the water from the house with the grey pipes in the images. But I ended up discarding that idea. It works fine just splashing the water onto the deck, and it is much simpler)

Assembling the Greenhouse

Assembling the greenhouse was just to follow a very complicated instruction manual!

This is a two person job, both for holding and moving parts, but also for interpreting the manual.

As we mounted the glass, we added postit's to the panes to avoid walking into them. And the postit's in dog height, were left on for a long time,.. :)

The glass panes are held in place with a rigid plastic profile, that can be hard to determine if it has been mounted properly. So it is worth double checking on the ceiling, as they are hard to reach again if they should come loose, once all glass has been mounted.

It is important to get a greenhouse with tempered glass, if you are going to stay inside for longer periods of time, or if kid's might play in there. You don't want large shards of glass falling form the ceiling when hit by a ball or bird.

We replaced the top of the desk with a stone plate, as a wooden top would probably not last long with the changing humidity and temperature.

Early Testrun

Checking for leaks during a rainfall, and trying out the newly assembled garden furniture.

An infrared heater is placed in the ceiling, for the evenings when the temperature drops, or the wind cools the house.

Skirting

An upright plank was used as skirting.

When placed perpendicular to the beams, the beams are cut so that they stick out 5mm, or the same distance as is between the planks of the deck. The skirting can then be screwed into the beam ends, using the same screws as for the deck.

When placed parallel to the beams, a peace of wood or wedge can be placed behind as a spacer (the red part in the sketch), to achieve the same 5mm gap.

Stone Edges

In some places, the deck is at level with the ground. So some concrete patio stones were placed upright in a bit of cement, to shield the boards from the wet earth.

Some screws were inserted into the beams, to keep the stones from touching the wood, as this would cause the wood to rot. (they can just be made out in the space between the deck and the stone )

Adding a Few Steps

I wanted to use the same wood for the steps as the deck, so I screwed and glued two pieces together to make it strong enough. I used a cardboard template to get the angles and height right. The white cardboard template can be seen where the side of the steps were bolted onto the support beam.

The sketch show the final size, and how the sides of the stairs are cut from a deck plank. The other sketch show how it is bolted onto the inside of the support beams. The deck planks ar 23mm thick, hence the 23x23mm notch at the top which allows the side to be mounted flush with the deck and skirting. If you use another thickness of planks, this should be adjusted accordingly.

You can easily add or remove a step by extending or shortening the sides.