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Installation of interior doors: step-by-step instruction

Do-it-yourself installation of interior doors does not require specialized construction skills.
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interior door installation


Do-it-yourself installation of interior doors does not require specialized construction skills.

Some models are sold already assembled.

In other cases, door designs come in disassembled form, which requires additional time and financial costs to install the door-frame and the door slab.

It is also necessary to decide beforehand whether the leaf opens to the slab or to the right, pull or push.

Below we offer a step-by-step instruction on how to install an interior door correctly

Sizes and configuration

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Prepare the following toolbox:

  • A leveling tool to control the vertical position of the frame.
  • Tape measure, ruler, permanent marker, pencil for marking.
  • A handsaw or a jigsaw for extensions and casings cutting.
  • Electric drill, cordless perforator, screw driver with wood and masonry drill bit sets.
  • A milling cutter to be used as a hardware. If it’s not there, a chisel with a hammer will do.
Rough Opening Height, mm Rough Opening Width, mm The nominal size of the door slab, mm
2055-2060 700-710 2000 600
2055-2060 800-810 2000 700
2055-2060 900-910 2000 800
2055-2060 1000-1010 2000 600+600
2055-2060 1330-1340 2000 600+600
2055-2060 1530-1540 2000 700+700

Prepare wedges with different dimensions, which will be used as a spacer for fixing the door-frame. Any instruction describing the interior doors installation says that self-tapping screws are used to fix it. Decide at once how the fastening/fixing/attachment will be made.

A hidden assembly method is preferable, which will require lifting bars. A good alternative is to put /install the door-frame on the anchors. They need to be screwed and pushed into the secret holes, which are then spackled and repainted.

Expendable materials and tools

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Expanding foam will be required. The installation of interior door slabs sometimes involves the need to narrow the rough opening. This involves the use of brick, which means that a finished cement-sand dry masonry mixture is required. Store the container to dissolve it with water and to stir until you get a homogeneous mix.

Buy a square trowel. It’s good to have a scraper at hand to remove the weatherboards before installing the casings made of MDF when the rough opening / hole in the wall is too large.

In other cases, both a wood chisel and a hammer will be required.

If after assembly of the frame and the door it will be turned out that the rough opening is too small, you have to remove the elements of the wall panel and dispose of the waste, so prepare trash bags.

If there are furniture, household appliances and interior objects in the adjacent rooms, cover them with polyethylene film.

The edges of the wall are treated with a spackle, mortar of cement. And to do that, you need an atomizer for humidifying, brushes for removing dust.

Step-by-step instruction for installing interior doors

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In order to install the doors on your own, it is enough to be able (know how) to use the above-mentioned tools.

The procedure starts with measurements. They must be accurate, as a door frame with a slab is chosen on their basis.

  • If you buy a unit in disassembled form, you’ll have to take the time to assemble the frame.
  • All the intended hardware is built in: lockset, handles, butt hinges.
  • A door-frame is installed, verticality and compliance with the required dimensions are checked.
  • The slab is attached with  an installed hardware and the weatherboards are finished.

Before a door is installed, the height and width of the aperture must be measured. This is done in three planes (along the floor, ceiling and in the middle) and two vertices on each side. The design in this case shall not be attached (tightly). The technological gap along the perimeter shall be between 4’’ and 15,7’’ (10 and 40 centimeters).

Extensions are installed if the depth of the hole/rough opening is much greater than the door-frame.

The casings are installed after the gaps are filled with expanding foam.

A more detailed step-by-step instruction includes seven steps.

Step 1. Door-frame assembly

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It(the door-frame) is assembled from wooden bars fixed/attached to each other in the form of a rectangle, unless a threshold is provided.

This type of interior door installation is used for WC, baths, technical rooms, balconies, greenhouses and storerooms, which must be closed tightly.

Other rooms has a P-shaped configuration in plan: I-configuration is used in other rooms: bedrooms, living rooms, dining rooms, etc. There are a number of features and nuances that you can deal with during the assembly/process.

Splinting and Connecting Ways

Methods of the Door-frame assembly

At a 45-degree angle

A beautiful but rather difficult way for an inexperienced builder. It is desirable to use a miter saw or a good hand mitre saw to saw the openings for buit-in equipment.

At a 90-degree angle

The most suitable option for a do-it*yourselfer without cabinet macker skills. You still have to use a mitre box to cut off the door-frame girder.

Recommended gap

The header is attached to the jambs with two self-tapping screws with anti-corrosion treatment.

Expert advice

For self-tapping screws that screw in into the MDF-elements, the holes must be pre-drilled with a drill bit, the diameter of which is three quarters less than the size of the screws.

In most cases, the manufacturer himself saws the blanks for the door-frame according to the size of the slab. Then it is enough to screw the design, fastening the elements with the screws included in the delivery package. If you have to do/start everything from scratch, the slab is taken, and the sidewalls, the upper beam and the threshold are cut along it. Work is best done on the floor.

In this case, two methods of fastening are used:

1. The header and stud are cut at an angle of 45 °. For people without cabinet maker skills, this method is difficult. Additional equipment will be required to do the even cut and correct geometry Make holes for self-tapping screws. Their axes should be perpendicular to the cut. At the final stage, the parts are applied to each other, if desired, they are glued and fastened with screws.

2. The plane of the cuts is perpendicular to the girder axis. The length of the side studs exceeds the height of the door slab by 0,12 in (3 mm) at the top and bottom, if a threshold is provided. Otherwise, a gap of 3/8’’’’ (10 mm) is made at the bottom. To attach the header to the studs, two self-tapping screws on each side are enough. The same applies to the sill beam.

Method 2 is the only one for door-frames with a threshold. Therefore, before hanging doors with a wooden door (slab) and a frame, determine the type of rough opening, and on the basis of this, select the method of the door-frame installation. And do not adjust the dimensions end-to-end. There should be 0,12 in (3 mm) gaps on all sides, which are necessary to pull out the stud freely without jamming.

Connection of the door-frame elements

The sequence of the door-frame design

  1. On a level surface, on a floor or on two shifted tables, you have to place a door-frame girder around the slab, and a cardboard is laid between the slab and the door-frame to form a gap.
  2. The upper end faces of the vertical girders of the door-frame are provided with a blank of the horizontal upper plank and the exact length of the header is measured;
  3. Saw cuts are better cut down with small teeth hack saw
  4. Attach the top of the door-frame(the header) to vertical girder; cardboard must be laid between the slab and the header to form the gap;
  5. When conjoining at right angles, the meeting stile preventing to attach the elements is first cut, then after creating a level plane; the screws are tighten up.
  6. If the saw cuts are made at an angle of 45°, the screws are turned perpendicular to the conjoining line through both girders;
  7. For door-frames without a threshold, the gap between the slab and the potential surface of the floor cover shall be between 5/16’’’’ and 7/8’’’’ (0.8 and 2.0 cm), depending on the purpose of the room and the type of floor covering.
  8. The threshold is made by analogy with the manufacture and attachment of the header at right angles.

Metal screws having a length of not less than 23,6 in (60 mm) shall be used to tighten down the header with side studs. For the first, each side takes three screws, while the other side takes two ones. To make the connection tight, strong/durable and reliable, a quarter is removed. A hacksaw and a chisel with a hammer are used for that. The length of the hole is equal to the width of the girder used in the manufacture of the stud.

  1. Saw off the header of the size we want (using a triangle and a hacksaw)
  2. Mark places of openings for built-in equipment on the «plank» of the header (marked by red lines).
  3. Saw the openings on the plank of the header with a hacksaw (in order not to damage the «front surface» of the door-frame, it is possible to put on it, for example, a piece of thin tin-plate, on the drawing it is painted with gray paint.
  4. With a sharp knife "cut through" (as deeply as possible) along the line of the future horizontal cut, from both sides.

For those who want to know how to install an interior door without a threshold, you must remember that you can cut parts at an angle of 45 degrees, and you will not have to remove a quarter. Another way is to install the header in width for the entire rough opening. This is necessary if it is significantly larger than the door-frame. Then the side supports are attached at right angles to a width that satisfies the dimensions of the door slab.

Assembling a door-frame with a header equal to the width of the upper rough opening zone

Door-frames with a wide lintel/header are assembled for the rough openings arranging in brick or foam concrete buildings to increase the bearing capacity and to ensure alignment with brickwork.

The length of header is equal to the width of the rough opening minus 1,96 in (5 mm). After sawing off a header of the desired length, draw the central axis of the part, distances to the hinge and pretend girder are marked in both directions from it.

Further door-frame assembling actions are performed according to standard technology.

Step 2. Hinges installation

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This is one of mandatory point of the step-by-step interior door installation. The process requires special attention and accuracy. Then the slab will open and close easily, without touching the door-frame, without friction or jamming. The opinion that two butt hinges are enough is wrong. It is better to use three turning knots (i.e., three hinges). This will prevent the possibility of sagging. The first point shall be placed in the place where the top hinge is located, then the middle hinge, and after the lower one.

The use of mortise and overhead hinge mechanisms is allowed. In the latter case, there is no need to make holes, otherwise, before installing the door, it is necessary to cut the material of the attachment size of the butt hinge on the slab and in the support. Marks of overall dimensions and places for fasteners are applied. After screwing in the self-tapping screws, the door-frame is installed vertically, the slab is hung and checked if it opens well and bears against the door-frame.

Step 3. Door-frame installation and door slab hanging

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Before installing, the rough opening should be prepared. The main thing is that there are no protrusions that prevent you from placing the door-frame. To install the door yourself, you need to remove the slab, and set the door-frame to a spirit level. Use a plumb rule to determine the deviation from the vertical axis.

MDF door installation options

For fixing MDF door-frames in the rough opening, it is recommended to use not self-tapping screws, but mounting metal plates used in the installation of drywall designs. Plates are often used in combination with anchor bolts. The number of fasteners is chosen depending on the forthcoming load.

The use of anchor plates is possible if a clean finish has not yet been made. Their installation will require the shaving and levelling of walls after the door-frame is attached.

The design is opened in the rough opening by prepared wooden wedges. This shall be done first with one stud, then with another, and then check the horizontality of the header and make control measurements.

The standard fixing method is anchoring. The jambs are drilled through and grooves are made in the face of the wall panel. This method of installation involves dowels from 5,9'' (150 mm) in length, but they will be visible. You will have to putty, glue or paint over.

The secret fastening is more complex. The fastener is a metal profile, as for plasterboard. The plates are attached to the wall with anchors. First, they make holes in the concrete so that the fastening can be sparkled.

Then you need to insert/hang the door. To do this, it is placed on pre-prepared plates. Having raised the slab, it is necessary to ensure that the mechanisms of the butt hinges are in their places. After that, check if it stands on the way of the door-frame when opening and closing.

The operation of the hardware must also be checked. By the way, handles and locksets are installed on the floor before assembly. Now, it’s important that nothing interferes with the normal operation of the door. Open it half way and make sure it keeps its own position, which is evidence of the verticality of the design.

Step 4. Foaming

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Rules for filling the gap with foam

The corners made of sawn timber scraps will help to precisely keep the centimeter technological gap under the polyurethane foam. Changing the depth of their immersion into the gap, at the same time align the door-frame in the opening.

It is better to buy foam with a dispenser. It is desirable to apply it in portions. First a thin layer, then an additional layer to fill all the space*gap*. In this way, the material can be saved, and not cut off excess/unnecessary foam after consolidation.

Now it's time to fill in the gaps between the booth and the wall. Close the door. The foam is applied in layers, in thin layers. First, the top of the volume is filled so that the foam does not protrude outward under its own weight. If it gets on a visible surface, you must immediately wipe off the excess with a dry cloth.

When the foam has already hardened, use special means to remove the polyurethane foam. After finishing work it is better not to use the doors for 24 hours. This is necessary for the complete drying of the foam.

Step 5. Door lockset and handles installation into a door slab

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According to the installation rules, to perform this type of work, you need to remove the slab. If the manufacturer has not made holes and grooves, you will have to make them yourselves. A milling cutter, chisels, drill are used. Locksets can be overhead and mortise. In the latter case, you will have to select the wood from the support, screw on the cover plate/overlays. And a lockset is inserted/screwed into the hole on the door slab with self-tapping screws. Then decorative cover plates/overlays are installed on the planes on both sides.

But nowadays most of the locks are built into the handles. Manufacturers pre-make holes in which you need to insert a handle with a drive pin. On the other side the second part is fixed. It is better not to change the installation order. The design is fastened with self-tapping screws come fitted with the handles. After screwing in, the faceplates are installed, which are fastened with latches. After that, the slab with hardware is placed on the awnings (hinges). It is important to check that the deadbolt moves freely and does not jam.

Step 6. Extension plates installation

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Step by step instruction at this stage of the installation looks like this


If the bar/plate is not part of the delivery package, buy the bar/plate of the same color.

Cut it in size so that the edge of the wall is completely closed.

Set/install the lateral/bypass extension and then fasten/fix the upper one along the header.

Methods for fastening the door-frame expanded by the extension in the rough opening

  1. Door slab
  2. Door-frame girder/Jamb
  3. Extension
  4. Walls
  5. A plank, used to connect a door-frame to a extension
  6. Expanding foam
  7. Solid board or gypsum plasterboard plank
  8. A girder, glued along the perimeter of the extension. Its size is calculated so that a 3/8 in gap (centimeter gap) remains between the girder and the wall.
  9. A girder, attached to the wall with screws along the vertical jambs, screw it so that the distance between the wall and the mounting planks/rails can be adjusted
  10. Screws

Expert advice

The most difficult thing is to supplement the door-frame with extensions, installed in the rough opening. There are two ways to carry out the planned finishing:

- glue girders with a length of 11,811-15,748 in (30-40 cm) around the perimeter of the extension, then glue the extension to the door-frame and fill the space with expanding sealing foam;

- screw the timber to the wall with five or six self-tapping screws, adjust the position of this peculiar door frame, then insert the extension into the groove and fill the gap with foam.

There are several fixing options. Some modifications of the plates/planks are designed to be placed in special grooves. Another case is when the additional plank is pressed by the door-frame, which means that the installation is necessary during the detachment of the door-frame. L-casing systems are also found when the extension is fixed on both sides.

Step 7. The casings fastening

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Options for framing interior doors

A. Attach the vertical plates to the planned fastening point

B. Carefully mark the starting points of the future work piece cutting, saw it down according to the marks at an angle of 45 °

C. The cross casings, pre-cut at an angle of 45 degrees, is applied to the install location point and mark the second point.

Expert advice

Before final fastening, the operation of the door must be checked: open and close several times. The trims should not stand in the way of the door slab movement.

A. Spike up the upper transverse/cross casing with the help of three galvanized or thin copper nails

B. Put a extensional/lineal vertical casing, installed from the side of the hinges location, mark the future cut line, do the same things with the opposite vertical casing

C. Attach the casings to the door-frame

The face of the door-frame should be flush with the wall surface. Attach the vertical piece to the header and make a cut mark that is ¼ in (half a centimeter) higher. Draw cutting lines, cut off excess/unnecessary. Now apply the side casings one after another.

The main thing is that the line of contact on top is at an angle of 45°. To attach the casing to the jambs, nail them with nails without caps, then they will be invisible. Adhesive binding is also used, but less efficiently. Better yet, use the combined method.

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