If your going to lay a new patio in your garden but have a drain cover in the way then you may be wondering if and how your going to pave over it. The good news is that you can and the even better news is that in most cases it’s really not that difficult either! I still remember my first paving job a good 10 years ago where I didn’t even know that there was a manhole cover in the way, had never done one before and yet I still managed to pull it off!
It doesn’t matter whether you are block paving or laying a new patio – The process is all the same and if your laying the new paving slabs yourself then you will already have the tools needed for the job! In this article we will look at the tools and products needed to pave over your manhole cover as well as a full step by step guide!
Which tools do I need to pave over a manhole cover?
To be honest there aren’t a huge amount of tools needed to pave over a drain and there is a good chance that you already have them to hand if your doing the paving your self but just to be sure, below is the full list of tools needed to pave over your manhole cover.
- Spirit level
- Tape measure
- Angle grinder
- Rubber mallet
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A spade is great for digging around your existing drain as well as mixing the sand & cement etc..
A spirit level will be needed to make sure that your new manhole cover is level to the surrounding paving. I often lay the paving slabs as close to and around the drain cover as possible making it easy to ensure that the new drain hole cover is at the same height and level.
A tape measure will be needed for the measuring and marking of each paving slab that is to go in and around the manhole cover, ready for cutting.
An angle grinder is needed to cut each paving slab to shape. You can use the smaller 4.5″ angle grinder which are easier for cutting awkward shapes etc., but here I have recommended the full sized 230mm (9″) angle grinder as most awkward cuts can still be done with one of these and the discs will last much, much longer. Make sure you use a concrete/stone/masonry diamond blade discs for cutting through the paving slabs.
A rubber mallet is the must have tool for tapping your paving slabs or block paving into place once your recessed manhole cover is in place.
Which materials do I need to pave over a manhole cover?
Other than the obvious sand and cement which we will get into more detail below, the only real product you will need to pave over a drain cover in your garden is another drain hole cover! You will need a recessed manhole cover to be more precise which will give you a depth within the cover itself allowing you to pave inside. Here are some examples below.
Here is the most standard sized recessed manhole cover measuring in at approximately 600x450mm with a depth of 65mm making it perfect for most paving jobs. This size can replace most existing rectangular manhole covers and we have even used them to turn a circular manhole cover into a rectangular one, making it easier to cut the slabs and fit into the new patio.
This manhole cover has the same dimensions as the one above but has a greater depth of 80mm – This usually means that it can withstand greater weight for those drain covers on your driveway where block paving will be used. It’s always best to check the weight capabilities of the drain cover being purchased to make sure it’s fit for purpose.
Whilst the majority of manhole covers are rectangular (600x450mm) it’s very possible that you will have a square 600x600mm drain cover. This one in particular has a depth of 80mm making it suitable for driveways where small to medium sized cars will be used, but you can always replace a square manhole cover with a rectangular one if this better suits your paving needs.
Make sure you plan ahead before paving over your manhole cover
Before any paving project I always plan ahead which is particularly important when there is a drain cover in the way. The first thing your always going to want to remember is that it’s always easier to raise a drain cover compared to lowering it so try and plan ahead to avoid lowering one.
You don’t just want to skim the surface of your existing manhole cover either as most recessed manhole covers have a minimum overall depth of 58mm (including the frame) and even more from 100mm for the deeper manhole covers that are to be used on driveways. This means that to avoid lowering your existing drain cover you will need your new patio or paving to be at a minimum height of 60mm (plus extra room for your mortar mix) above your existing ground level which will allow you to easily install your new cover above your existing one.
If your unable to raise your existing drain cover due to the damp course on your property or any other reasons then it’s best to remove your existing manhole cover and see how deep the concrete is that’s holding it in place. You will usually have a brick built wall within with a minimum of around 6 inches of concrete. You will want to avoid touching the brickwork where possible (I’ve never had to touch them) and just knock out the concrete to a depth that’s suitable for your new manhole cover. This is best done when you pave up to the manhole cover to give you an accurate height/depth which I’ll get into more detail about below.
In almost all cases I have been able to raise the new patio to a suitable height, allowing me to raise the drain cover.
Step by step guide showing you how to pave over your manhole cover
Step 1 – Pave up to and around your existing manhole cover
Never ever install your new manhole cover before laying your paving as it would be all to easy to end up at the wrong height! Instead pave up to your existing drain cover and if possible, around it. This way you will be able to find the exact height to where your new manhole cover needs to be by simply using a spirit level.
Step 2 – Make a mortar mix ready to start installing your new manhole cover
I’m sure lots of people will give you their own views on the best mortar mix so I’m just going to tell you what works for me. I use a mix of 3:1 (3 parts sharp sand to 1 part cement).
The reason I use sharp sand, other than the fact that this is what I use when laying my paving anyway is that I feel ballast has too many large stones in it for such a small amount of mortar being used, weakening the structure, as well as the stones being able to get in the way when tapping the frame to the new manhole cover into place.
I avoid building sand as it is more likely to crack under pressure, hence why shed bases are built with ballast as opposed to builder’s sand. Sharp sand is a nice, between the 2, type sand.
I do lay my paving with a 5:1 mix and it’s probably fine doing it this way for the installation of a manhole cover but I like to use a 3:1 mix for added strength.
Step 3 – It’s time to install your new manhole cover
Providing that you are going to be raising your existing drain cover then the first thing you are going to want to do is remove your existing one and lay a bed of mortar around the perimeter of your drain hole, a little higher than needed.
Next remove your new manhole cover from the frame within and put to one side. By just using the outer frame you will be able to see in both sides making sure that your mortar mix is compacted all the way through.
Simply place the frame to your manhole cover on top of your mortar bed and tamper it down evenly, one side at a time until it’s nearly level with the surrounding paving. From here I use piece of 3×3 wood, long enough to reach the paving from one side, over the manhole cover and over to the other side. This way if you tap it down using a mallet, you can only end at the perfect height to the surround paving. You can always use your spirit level for this if you have no 3×3 posts lying around.
Once you are happy with the height of your new manhole cover (frame) then use your mortar mix to go along the inside, filling in any gaps and create a smooth finish using a trowel. Once complete, lay some mortar along the outside of the frame to ensure that it will be secure once set but try not to create too thick a layer as you need to allow room for your surround paving.
If you are needing to lower your existing manhole cover then all of the above steps are still correct but before you do so, you will need to remove your existing manhole cover and remove or lower the existing cement that’s holding it in place.
In the past I have had success simply using my 9″ grinder along the inside of the manhole wall making it easier to knock out the cement from the cut above. I would avoid using a large breaker as you run the risk of damaging the bricks below, however a handheld breaker should be fine to use and will give you more control.
Once your new manhole cover is in place and you are happy, use a hose to wash down any loose cement that has managed to find it’s way into the manhole, being careful of splashing and ruining your work. Wait a good 24 hours at least for the mortar to set before continuing to the next step.
Step 4 – Cut and lay your surrounding paving slabs
If you’ve layed your new paving slabs yourself then this bit should come naturally. If you’ve never layed your own patio but are thinking of giving it a go then you can read my full guide here.
Cutting your paving slabs around a new drain hole cover can be tricky, especially if your new manhole cover is diagonal compared to the rest of your paving like the one pictured.
In theory, all you need to do is measure and mark each paving slab before cutting it into shape with your angle grinder (with a masonry blade ofcourse). If there are awkward cuts like the one above then you can use cardboard and a Stanley knife to create templates, or simply place your whole slab into place and resting on top of your new manhole cover whilst you mark where each angle is. Although this can be easier said than done!
Once cut, just lay the paving slabs around your new drain cover as you would lay your slabs anywhere else – With a mortar mix and tapping the slab into place. Cutting the slabs to fit the inside of your recessed manhole cover can be a little more tricky due to the handles.
What I tend to do is cut the paving slab(s) to the perimeter of the manhole cover and once done, fill the manhole cover with cement and temporarily place the slab into place, covering the handle(s). I then mark on the slab where the handles are from side to side, remove the handle covers, and use these as a template to draw around before making my cuts. This works perfectly for me!
Once you are happy with your cuts, lay then inside your manhole cover as you would anywhere else and tamper down until a perfect height with all 4 edges. Once done, have 2 of you lift your manhole cover and place into the frame, finishing it off!
My overall thoughts on replacing a manhole cover with a recessed paved one
Paving over a manhole cover really isn’t all that hard and if your capable of laying your new patio or block paving yourself then the chances are that you will be able to install a recessed drain cover too.
Just remember to check the depth of the drain cover that your purchasing and that it can handle the weight that you intend to use it for. For example, the one pictured here could handle up to 5 tonnes which was more than adequate for a back garden and could likely be used for a drive too since the majority of cars way less than 2 tonnes, although the 10 tonne ones would be the ones I’d still use on driveways just to be on the safe side!
This turned out to be a much longer article than I had anticipated – Honestly sometimes once I start writing I just get carried away! So much so that I’ve most probably missed something so if you have any questions then please do comment below and I’ll respond as quickly as possible! Alternatively you can pop over to our forum and ask your question there where we all try to answer each others questions.